Дисертації: "Current load"

1

Ma, Shuhan. "Load-current response to severe changes of voltage." Thesis, KTH, Elektroteknisk teori och konstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203894.

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Electric loads, such as computers, lamps, refrigerators and heaters connected to low-voltage distributionsystems in homes and offices differ widely in how their current responds to changes in the applied voltage.These voltage changes could be a total collapse of the voltage, a weak or strong reduction of amplitude,or a sudden phase-shift.This thesis investigates the currents into some modern power-electronic interfaced loads, at sub-cycletimescales, in response to sudden changes of AC voltage magnitude. One reason for this interest was anearlier project about fault-location methods in which the necessary level of modeling of loads wasquestioned [1]. A related issue that is also investigated is the response of such loads when Wye-connectedin a three-phase system with a high-impedance neutral such as a broken conductor.Several related matters have been studied a lot in other work. For example, active and reactive powerconsumptions of loads can change in response to the variation of voltage magnitude and frequency.Studies of power system oscillations, and angle and voltage stability, typically make use of such models.At distribution level, the relation of power consumption of loads to the feeder voltage has been includedin studies of Conservation Voltage Reduction (CVR). In these examples, the variation of voltage is typicallysmall, and the result is a value that summarizes an entire cycle (active or reactive power) without givinginformation about the current’s faster changes. Studies of voltage dip tolerance have instead workedwith larger changes of voltage, and short and variable durations, but without the resulting current beingthe interest.This thesis starts with a literature survey about different types of modern loads with differentcharacteristics, especially electronic loads which have become a far greater proportion of the totaldistribution-system load over the past several decades. It is known that the number of the electronicdevices has increased significantly due to the boom in the consumer electronic market. The most commonexamples of these loads include: computers, monitors, TVs and DVD players. Based on a survey of loadbehaviors and models, the current response of these loads to the voltage dips or recoveries are modeledby circuit simulation. Measurements of the currents into some computer equipment were performedwith voltage dips and recoveries, and compared to the results from models. The voltage amplitude dropsto 25%, 50% or 75% of its original value, and recovers afterwards. The current response is studied, focusingmainly during a short time period up to a few AC cycles. A similar mixture of simulation and measurementis then used to study the situation of the potential that arises at the neutral point of a three-phaseconnected electronic load when the neutral conductor has a high resistance.
Elektriska laster i hem och kontor, såsom datorer, lampor, kylskåp och värmare, anslutna tilllågspänningsdistributionsnätet, varierar kraftigt i hur deras strömmar reagerar till förändringar ispänningen, vilka kan exempelvis vara en svag eller stark minskning av spänningsamplituden eller enplötslig fasförskjutning.Denna avhandling undersöker strömmarna i vissa moderna slags laster, vilka har effektelektroniskgränsnitt mellan nätet och effektförbrukningen. Strömmarna betraktas även på tidsskalor mindre än enperiod av nätfrekvensen. En anledning till intresset var ett tidigare projekt om fellokaliseringsmetodersom ifrågasatte den nödvändiga nivån av lastmodellering [1]. En relaterad fråga som också utreds ärbeteendet av sådana laster när de är Y-anslutna i ett tre-fas system med hög impedans i nolledaren.Flera aspekter av lastmodellering har studerats i tidigare arbete. Aktiv och reaktiv strömförbrukning avlaster som konsekvens av spänningsamplitud och frekvensen har studerats för modellering av elsystemetssvängningar samt vinkel- och spänningsstabilitet. I distributionsnätet har förhållandet mellan lastersströmförbrukning spänningsamplituden inkluderats i studier av ”CVR” (conservation voltage reduction). Idessa exempel är variationen av spänningen vanligtvis små och resultatet är ett värde som sammanfattaren hel cykel (aktiv eller reaktiv effekt) utan att ge information om snabbare förändringar. Studier avtolerans av laster till spänningssjunkningar har istället arbetat med större ändringar av spänning och kortoch variabel varaktigheter, men utan att ta intresse på den resulterande strömmen.Avhandlingen inleds med en litteraturstudie om olika typer av moderna laster med olika egenskaper,särskilt elektroniska laster som har blivit en mycket större andel av distributionnätets belastning under desenaste decennierna. Antalet elektroniska enheter har ökat betydligt: vanliga exempel av sådana laster ärdatorer, bildskärmar, TV och DVD-spelare. Baserat på litteratur om sådana laster och deras modeller, harresponsen av dessa laster till spänningssjunkningar eller återställningar modelleras genomkretssimuleringar. Mätningar har också utförts, av strömmarna i några datorutrustningar, vid spänningarsom sjunker med 25%, 50% eller 75% av det ursprungliga värdet och återställs efteråt. Dessa mätningarjämförs med resultaten från modellerna. Tidsramen av intresse är från millisekunder upp till någraperioder av nätfrekvensen. En liknande kombination av simulering och mätning har också använts för attstudera situationen där faror kan uppstå vid bruten nolledare i ett trefassystem.

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2

Jonsson, Erik. "Load Current Interruption in Air for Medium Voltage Ratings." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24327.

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Load break switches (LBSs) are common inside metal clad switchgear assemblies where space is a limiting factor. SF6 is usually used in this application due to its superior electrical characteristics, but is unfortunately also a strong greenhouse gas. Therefore development of new products, utilizing air which is an environmental friendly alternative, is in progress. Since air has much lower dielectric strength than SF6, the main challenge with this is therefore to reduce the size. Compact SF6 products have created a retrofit market, and in many existing installation sites larger products will not fit. Current interruption is a complex process and depends on several parameters, and it is not straight forward to optimize the design of a medium voltage (MV) switch. Numerical simulation which is a common for product development in other areas is difficult for this application. Due to the long dominance of SF6 products, little research has been published about the design criteria for LBS technology in air. The scope of the thesis covers current interruption of MV LBSs in air with respect to various design parameters, such as nozzle geometry, nozzle materials, gas flow, and contact movement. Both gas blow-assisted current interruption (associated with puffer breakers) and ablation-assisted current interruption are addressed. The material in the nozzle can enhance the interruption capability. Such a nozzle material is called ablation material. When the arc is burning close to the surface of an ablation material, gas is evaporated which cools the arc. This technology is used to some extent for low voltage switchgear, but much less for higher voltages. The objective is therefore to investigate the potential of this technology for the MV LBS application. All work is done experimentally with similar test conditions as are used for product type testing. A direct powered MV laboratory and a test switch are built. The test switch is designed particularly for parameter studies. The result from air blow experiments reveal the minimum upstream pressure drop required for current interruption for various basic nozzle geometries, and at different contact positions. One study is particular relevant for the 24 kV / 630 A class, and it is found that 0.25 - 0.3 bar upstream pressure drop appears to be a threshold value for successful interruption. It is also presented how the minimum upstream pressure drop varies for different MV LBS ratings. The results show that the needed pressure drop is approximately proportional, both towards the current and towards the rate of rise of recovery voltage. This investigation is made so that the majority of all MV LBS ratings (7 - 52 kV and up to 900 A) are covered. From the ablation experiments it was found that high content of hydrogen in the ablation material is favorable for enhancing the current interruption capability. In a comparison experiment between different polymers, polypropylene shows best interruption capability. This material was therefor applied as ablation material in the test switch, and tested in the MV laboratory. The results reveal high capability to interrupt the thermal phase (over the needs for most MV LBSs), but also that the transient recovery voltage several milliseconds after current zero often leads to dielectric re-ignition. This is opposite to a puffer breaker where the thermal interruption instead appears to be the crucial part.

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3

Moore, Jonathan E. "Frequency-based load sharing in current-mode-controlled buck converters." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA362884.

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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, March 1999.
"March 1999". Thesis advisor(s): John G. Ciezki, Robert W. Ashton. Includes bibliographical references (p. 103-105). Also available online.

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4

Su, Yipeng. "High Frequency, High Current 3D Integrated Point-of-Load Module." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51248.

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Point-of-load (POL) converters have been used extensively in IT products. Today, almost every microprocessor is powered by a multi-phase POL converter with high output current, which is also known as voltage regulator (VR). In the state-of-the-art VRs, the circuits are mostly constructed with discrete components and situated on the motherboard, where it can occupy more than 1/3 of the footprint of the motherboard. A compact POL is desirable to save precious space on motherboards to be used for some other critical functionalities. Recently, industry has released many modularized POL converters, in which the bulky inductor is integrated with the active components to increase the power density. This concept has been demonstrated at current levels less than 5A and power density around 600-1000W/in3. This might address the needs of small hand-held equipment such as smart phones, but it is far from meeting the needs for the applications such as laptops, desktops and servers, where tens and hundreds of amperes are needed. A 3D integrated POL module with an output current of tens of ampere has been successfully demonstrated at the Center for Power Electronic Systems (CPES), Virginia Tech. In this structure, the inductor is elaborated with low temperature co-fire ceramic (LTCC) ferrite, as a substrate where the active components are placed. The lateral flux inductor is proposed to achieve both a low profile and high power density. Generally, the size of the inductor can be continuously shrunk by raising the switching frequency. The emerging gallium-nitride (GaN) power devices enable the creation and use of a multi-MHz, high efficiency POL converter. This dissertation firstly explores the LTCC inductor substrate design in the multi-MHz range for a high-current POL module with GaN devices. The impacts of different frequencies and different LTCC ferrite materials on the inductor are also discussed. Thanks to the DC flux cancellation effect, the inverse coupled inductor further improves the power density of a 20A, 5MHz two-phase POL module to more than 1kW/in3. An FEA simulation model is developed to study the core loss of the lateral flux coupled inductor, which shows the inverse coupling is also beneficial for core loss reduction. The ceramic-based 3D integrated POL module, however, is not widely adopted in industrial products because of the relatively high cost of the LTCC ferrite material and complicated manufacturing process. To solve that problem, a printed circuit board (PCB) inductor substrate with embedded alloy flake composite core is proposed. The layerwise magnetic core is laminated into a multi-layer PCB, and the winding of the inductor then is formed by the copper layers and conventional PCB vias. As a demonstration of system integration, a 20A, 1.5MHz integrated POL module is designed and fabricated based on a 4-layer PCB with embedded flake core, which realizes more than 85% efficiency and 600W/in3 power density. The application of standardized PCB processes reduces the cost for manufacturing the integrated modules due to the easy automation and the low temperature manufacturing process. Combining the PCB-embedded coupled inductor substrate and advanced control strategy, the two-phase 40A POL modules are elaborated as a complete integrated laptop VR solution. The coupled inductor structure is slightly modified to improve its transient performance. The nonlinearity of the inductance is controlled by adding either air slots or low permeability magnetic slots into the leakage flux path of the coupled inductor. Then the leakage flux, which determines the transient response of the coupled inductor, can be well controlled. If we directly replace the discrete VR solution with the proposed integrated modules, more than 50% of the footprint on the motherboard can be saved. Although the benefits of the lateral flux inductor have been validated in terms of its high power density and low profile, the planar core is excited under very non-uniform flux. Some parts of the core are even pushed into the saturation region, which totally goes against the conventional sense of magnetic design. The final part of this dissertation focuses on evaluating the performance of the planar core with variable flux. The counterbalance between DC flux and AC flux is revealed, with which the AC flux and the core loss density are automatically limited in the saturated core. The saturation is essentially no longer detrimental in this special structure. Compared with the conventional uniform flux design, the variable flux structure extends the operating point into the saturation region, which gives better utilization of the core. In addition, the planar core with variable flux also provides better thermal management and more core loss reduction under light load. As conclusions, this research first challenges the conventional magnetic design rules, which always assumes uniform flux. The unique characteristics and benefits of the variable flux core are proved. As an example of taking advantages of the lateral flux inductor, the PCB integrated POL modules are proposed and demonstrated as a high-density VR solution. The integrated modules are cost-effective and ready to be commercialized, which could enable the next technological innovation for the whole computing and telecom industry.
Ph. D.

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5

Garcia, Robert John. "THE EFFECTS OF COMPENSATION ON LOAD TRANSIENT RESPONSE IN SWITCHED MODE POWER CONVERTERS." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291724.

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6

Lam, Hoi-yee. "Voltage-current trajectory a 2-dimensional approach to understand electrical load signatures /." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B3890861X.

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7

Lam, Hoi-yee, and 林凱儀. "Voltage-current trajectory: a 2-dimensional approach to understand electrical load signatures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3890861X.

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8

Suh, Inyoung. "Determining the load composition in commercial buildings based upon harmonic current characteristics /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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9

Forslund, Johan. "Experimental Results of a Load-Controlled Vertical Axis Marine Current Energy Converter." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-268867.

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This thesis investigates the load control of a marine current energy converter using a vertical axis turbine mounted on a permanent magnet synchronous generator. The purpose of this thesis is to show the work done in the so far relatively uncharted territory of control systems for hydro kinetic energy conversion. The work is in its early stage and is meant to serve as a guide forfuture development of the control system. An experimental power station has been deployed and the first results are presented. A comparison between three load control methods has been made; a fixedAC load, a fixed pulse width modulated DC load and a DC bus voltage control of a DC load. Experimental results show that the DC bus voltage control reduces the variation of rotational speed with a factor of 3.5. For all three cases, the tip speed ratio of the turbine can be kept close to the expected optimal tip speed ratio. However, for all three cases the average extracted power was significantly lower than the average power available in the turbine times the estimated maximum power coefficient. A maximum power point tracking system, with or without water velocity measurement, should increase the average extracted power. A simulation model has been validated using experimental data. The simulated system consists of the electrical system and a hydrodynamic vortex model for the turbine. Experiments of no load operation were conducted to calibrate the drag losses of the turbine. Simulations were able to predict the behaviour in a step response for a change in tip speed ratio when the turbine was operated close to optimal tip speed ratio. The start position of the turbine was varied in the simulation to view the influence on the step response from a changed turbine position relative to the direction of the water flow.

Funders: J Gust Richert, Bixia Miljöfond

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10

Nyhlén, Erik. "Control of marine current energy conversion system." Thesis, Uppsala University, Electricity, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-129988.

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This thesis involves the development of a system for control of a marine current energy conversion system. The control system is developed on the principles of load control, i.e. it aims to control the rotational speed of the turbine by controlling the power extracted from the generator. The system operates by feedback of the generator DC-voltage and current as well as the speed of the water current passing through the turbine. An IGBT-transistor controlled by an AVR-microcontroller executes control of the generator and hence the turbine. A digitally implemented PID-controller serves as the fundamental automatic control regime. The control system can be operated from a PC-application connected to the microcontroller through a serial wire connection. From the graphical user interface ofthe PC-application the system operator can set the system control parameters and monitor the state of the generator and turbine. The control system can be set to keep the turbine operating at a desired tip speed ratio, rotational speed or generator voltage. Further, for purposes of indoor testing of the control system a separate system, a motor control system, was developed as a part of this thesis work. The purpose of the motor control system is to enable simulating the behavior of a turbine with a motor driving the generator instead of an actual turbine. The motor control system operates by control of an ACS800 variable frequency drive that is connected to the motor. The motor control system allows its operator to feed in data describing the variations in water speed over time as well as data describing how the simulated turbine's power coefficient depends on its tip speed ratio. From this data the motor control system continuously calculates the torque that should be put on the generator axis by the motor. Results from test runs of the system show that the performance of the system is good. The system responds quickly to changes in the control parameters. Also the system manages to keep the specified control parameter quite well even during rapid changes in the water speed.

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11

Gustafsson, Karin. "Ion Current Dependence on Operating Condition and Ethanol Ratio." Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8053.

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This masters thesis investigates the possibility to estimate the ethanol content in the fuel using ion currents. Flexible fuel cars can be run on gasoline-ethanol blends with an ethanol content from0 to 85 percentage. It is important for the engine control system to have information about the fuel. In todays cars the measurements of the fuel blend are done by a sensor. If it is possible to do this with ion currents this can be used to detect if the sensor is broken, and then estimate the ethanol content until the sensor gets fixed. The benefit

of using ion currents is that the signal is measured directly from the spark plug and therefore no extra hardware is needed. To be able to see how the ethanol ratio affects the ion currents, the dependencies of the operating point have been investigated. This has been done by a literature review and by measurements in a Saab 9-3. Engine speed, load, ignition timing, lambda and spark plugs effects on the ion currents are especially studied. A black box model for the ion currents dependence on operating point is developed. This model describes the engine speed, load and ignition timing dependencies well, but it can not be used to estimate the ethanol ratio.

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12

Pollock, Helen Geraldine Phyllis. "A series-parallel load-resonant converter for a controlled-current arc-welding power supply." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/4191/.

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A power supply incorporating a series-parallel load-resonant converter, capable of very efficient operation over a wide range of output power is presented. The series-parallel load-resonant converter is shown to have three pairs of resonant frequencies. Operation of the circuit at each of these resonant frequencies maintains zero current switching and high frequency operation. Design mathematics is developed which allow series-parallel load-resonant converters to be designed with specific resonant frequencies and circuit resistances. A new method of power control for series-parallel load-resonant converters is presented; the power delivered to the circuit and hence the load is shown to var substantially depending on which resonant frequency the circuit is excited at. Two series-parallel load-resonant converters are designed simulated, constructed and tested. There is good agreement between the simulation and experimental results. One of the circuits produces an output current of 200 A while the second demonstrates the new power control technique pulsing between 55 A and 145 A while running at frequencies of 63 kHz and 100 kHz. The new power supply is particularly suited to arc-welding. It contains an active rectifier and draws near unity power factor.

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13

Lee, John C. "Magamp post-regulator applied to a quasi-resonant converter and magamp operation under extreme load condition in a PWM converter." Thesis, This resource online, 1988. http://scholar.lib.vt.edu/theses/available/etd-11072008-063123/.

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14

ANDERSSON, JOHAN, and RICKARD HÖGLUND. "Electric Load Driven Longboard." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279809.

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This bachelor’s thesis aims to show an extensive overview of all the parts that build up an electric load driven longboard and see if a load controlled longboard can be seen as a safe, comfortable and convenient alternative to the more common remote controlled longboard. The thesis will also answer how weight can be measured on a longboard in the most effective way, what the most comfortable riding technique is and what a good motor-battery configuration to be able to travel at 30 km/h and 10 km would be. The longboard measures the weight distribution with load cells located between the deck and the trucks. An Arduino translates the input from the load cells to a certain speed and then sends it to an ODrive which controls a BLDC motor that is powered by two LiPo batteries. The results show that a load controlled longboard can very well be seen as a good alternative if right riding technique is used. The best technique is when the longboard accelerates when the rider tilts and keeps a constant speed when the rider stands straight. The best way to measure the weight is to fasten the trucks with hinges which lets the load cells register weight without anything interfering. Not all tests could be done because of Covid-19 but a measured top speed of 15 km/h with a high gear ratio is a promising result for the future when more suitable gear ratios will be tested to try to reach the goal of 30 km/h.
Det här kandidatexamensarbetet strävar efter att visa en omfattande överblick på alla delar som bygger upp en elektrisk lastdriven longboard och se om en laststyrd longboard kan ses som ett säkert, komfortabelt och behändigt alternativ till den vanligare radiostyrda longboarden via handkontroll. Det här arbetet kommer också svara på hur vikt kan mätas på en longboard på ett så effektivt sätt som möjligt, vad som är den mest bekväma åkstilen och vad är en bra motor-batteri konfiguration för att kunna åka i 30 km/h och nå 10 km skulle vara. Longboarden mäter viktfördelningen med lastceller som är placerade mellan brädan och truckarna. En Arduino omvandlar indatan från lastcellerna till en specifik hastighet som den sedan skickar till en ODrive som kontrollerar en borstlös likströmsmotor som i sin tur är driven av två LiPo batterier. Resultaten visar att en laststyrd longboard kan mycket väl ses som ett bra alternativ om rätt åkstil används. Den bästa stilen är att longboarden accelererar när åkaren lutar sig och håller en konstant hastighet när åkaren står rakt. Det bästa sättet att mäta vikt är att montera truckarna på gångjärn som låter lastcellerna mäta vikt utan att något stör. Alla tester kunde inte utföras på grund av Covid-19 men en uppmätt topphastighet på 15 km/h med en hög utväxling är ett lovande resultat för framtiden när lämpligare utväxlingar kommer testas för att försöka nå målet på 30 km/h.

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Wu, Long. "Separating Load Torque Oscillation and Rotor Faults in Stator Current Based-Induction Motor Condition Monitoring." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14545.

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Stator current spectral analysis techniques are usually used to detect rotor faults in induction machines. Magnetic field anomalies in the airgap due to the rotor faults result in characteristic side-band harmonic components in the stator current spectrum, which can be measured as rotor fault signatures. A position-varying load torque oscillation at multiples of the rotational speed, however, has exactly the same effect. Stator current harmonics due to a load torque oscillation often obscure and even overwhelm rotor eccentricity fault detection since the magnitude of load oscillation induced harmonics is usually much larger. Although previous research has suggested some methods to differentiate between these two effects, most of them rely heavily on the accurate estimation of motor parameters. The objective of this research is to develop a far more practical and computationally efficient method to detect rotor faults effectively in the presence of a load torque oscillation. A significant advantage of the proposed scheme is that it does not need any knowledge of motor parameters. The normalized negative sequence information induced by a mixed rotor eccentricity in the stator current or terminal voltage space vector spectra, serves as a reliable rotor fault indicator to eliminate load oscillation effects. Detailed airgap magnetic field analysis for an eccentric motor is performed and all machine inductance matrices as well as their derivatives are reformulated accordingly. Careful observation of these inductance matrices provides a fundamental understanding of motor operation characteristics under a fault condition. Simulation results based on both induction motor dynamic model and Maxwell 2D Finite Element Model demonstrate clearly the existence of the predicted rotor fault indicator. Extensive experimental results also validate the effectiveness and feasibility of the proposed detection scheme.

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16

Yao, Qifeng. "Experimental Investigation and Statistical Analysis of Entrainment Rates of Particles in Suspended Load." Kyoto University, 2019. http://hdl.handle.net/2433/244513.

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17

Lízner, Václav. "Nízkofrekvenční aktivní umělá zátěž." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316439.

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This diploma thesis is focused on synthetic loads, especially electronically controlled loads. The thesis analyse principles of mechanically and electronically controlled loads and theirs operation modes. The paper also carried out a search of AC loads available on the market. The parameters of the AC load were based on the requirements provided by client. The functionality of the designed load is verified by simulation. The thesis continues with realization of the designed schematics and bringing the load to function. At the last section of the thesis are detail parameters of the designed load verified by measurement.

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Gannett, Robert Ashley. "Control Strategies for High Power Four-Leg Voltage Source Inverters." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34251.

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In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies. Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone.
Master of Science

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Okubo, Hitoshi, Masahiro Hanai, Hiroki Kojima, and Naoki Hayakawa. "Progress in Development of Superconducting Fault Current Limiting Transformer (SFCLT)." IEEE, 2011. http://hdl.handle.net/2237/20728.

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20

Danilovic, Milisav. "Active Source Management to Maintain High Efficiency in Resonant Conversion over Wide Load Range." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/76618.

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Анотація:

High-frequency and large amplitude current is a driving requirement for applications such as induction heating, wireless power transfer, power amplifier for magnetic resonant imaging, electronic ballasts, and ozone generators. Voltage-fed resonant inverters are normally employed, however, current-fed (CF) resonant inverters are a competitive alternative when the quality factor of the load is significantly high. The input current of a CF resonant inverter is considerably smaller than the output current, which benefits efficiency. A simple, parallel resonant tank is sufficient to create a high-power sinusoidal signal at the output. Additionally, input current is limited at the no-load condition, providing safe operation of the system. Drawbacks of the CF resonant inverter are associated with the implementation of the equivalent current source. A large input inductor is required to create an equivalent dc current source, to reduce power density and the bandwidth of the system. For safety, a switching stage is implemented using bidirectional voltage-blocking switches, which consist of a series connection of a diode and a transistor. The series diode experiences significant conduction loss because of large on-state voltage. The control of the output current amplitude for constant-frequency inverters requires a pre-regulation stage, typically implemented as a cascaded hard-switched dc/dc buck converter. The pre-regulation also reduces the efficiency. In this dissertation, a variety of CF resonant inverters with two input inductors and two grounded switches are investigated for an inductive-load driver with loaded quality factor larger than ten, constant and high-frequency (~500 kHz) operation, high reactive output power (~14 kVA), high bandwidth (~100 kHz), and high efficiency (over 95 %). The implementation of such system required to question the fundamental operation of the CF resonant inverter. The input inductance is reduced by around an order of magnitude, ensuring sufficient bandwidth, and allowing rich harmonic content in the input current. Of particular importance are fundamental and second harmonic components since they influence synchronization of the zero-crossing of the output voltage and the turn-on of the switches. The synchronization occurs at a particular frequency, termed synchronous frequency, and it allows for zero switching loss in the switches, which greatly boosts efficiency. The synchronous conditions were not know prior this work, and the dependence among circuit parameters, input current harmonics, and synchronous frequency are derived for the first time. The series diode of the bidirectional switch can reduce the efficiency of the system to below 90 %, and has to be removed from the system. The detrimental current-spikes can occur if the inverter is not operated in synchronous condition, such as in transients, or during parametric variations of the load coil. The resistance of the load coil has a wide variance, five times or more, while the inductance changes as well by a few percent. To accommodate for non-synchronous conditions, a low-loss current snubber is proposed as a safety measure to replace lossy diodes. The center-piece of the dissertation is the proposal of a two-phase zero-voltage switching buck pre-regulator, as it enables fixed frequency and synchronous operation of the inverter under wide parametric variations of the load. The synchronous operation is controlled by phase-shifting the switching functions of the pre-regulator and inverter. The pre-regulator reduces the dc current in the input inductors, which is a main contributor to current stress and conduction losses in the inverter switches. Total loss of the inverter switches is minimized since no switching loss is present and minimal conduction losses are allowed. The dc current in the input inductors, once seen as a means to transfer power to load, is now contradictory perceived as parasitic, and the power is transferred to the load using a fundamental frequency harmonic! The input current to the resonant tank, previously designed to be a square-wave, now resembles a sine-wave with very rich harmonic content. Additionally, the efficiency of the pre-regulator at heavy-load condition is improved by ensuring ZVS for with an additional inductive tank. The dissertation includes five chapters. The first chapter is an introduction to current-fed resonant inverters, applications, and state-of-the-art means to ensure constant frequency operation under load's parametric variations. The second chapter is dedicated to the optimization of the CF resonant inverter topology with a dc input voltage, two input inductors, and two MOSFETs. The topology is termed as a boost amplifier. If the amplifier operates away from the synchronous frequency, detrimental current spikes will flow though the switches since the series diodes are eliminated. Current spikes reduce the efficiency up to few percent and can create false functioning of the system. Operation at the synchronous frequency is achieved with large, bulky, input inductors, typically around 1-2 mH or higher, when the synchronous frequency follows the resonant frequency of the tank at 500 kHz. The input inductance cannot be reduced arbitrarily to meet the system bandwidth requirement, since the synchronous frequency is increased based on the inductance value. The relationship between the two (input inductance and the synchronous frequency) was unknown prior this work. The synchronous frequency is determined to be a complicated mathematical function of harmonic currents through the input inductors, and it is found using the harmonic decomposition method. As a safety feature, a current snubber is implemented in series with the resonant tank. Snubber utilizes a series inductance of cable connection between the tank and the switching stage, and it is more efficient than the previously employed series diodes. Topology optimization and detailed design procedure are provided with respect to efficiency and system dynamics. The mathematics is verified by a prototype rated at 14 kVA and 1.25 kW. The input inductance is reduced by around an order of magnitude, with the synchronous frequency increase of 2 %. The efficiency of the power amplifier reached 98.5 % and might be improved further with additional optimization. Silicon carbide MOSFETs are employed for their capability to operate efficiently at high frequency, and high temperature. The third chapter is dedicated to the development of the boost amplifier's large signal model using the Generalized State-space Averaging (GSSA) method. The model accurately predicts amplifier's transient and steady-state operation for any type of input voltage source (dc, dc with sinusoidal ripple, pulse-width modulated), and for either synchronous or non-synchronous operating frequency. It overcomes the limitation of the low-frequency model, which works well only for dc voltage-source input and at synchronous frequency. As the measure of accuracy, the zero-crossing of the resonant voltage is predicted with an error less than 2° over a period of synchronous operation, and for a range of interest for input inductance (25 μH – 1000 μH) and loaded-quality factor (10 – 50). The model is validated both in simulation and hardware for start-up transient and steady-state operation. It is then used in the synthesis of modulated output waveforms, including Hann-function and trapezoidal-function envelopes of the output voltage/current. In the fourth chapter, the GSSA model is employed in development of the PWM compensation method that ensures synchronous operation at constant frequency for the wide variation of the load. The boost amplifier is extended with a cascaded pre-regulator whose main purpose is to control the output resonant voltage. The pre-regulator is implemented as two switching half-bridges with same duty-cycle and phase-shift of 180°. The behavior of the cascaded structure is the same as of the buck converter, so the half-bridges are named buck pre-regulators. ZVS operation is ensured by putting an inductive tank between the half-bridges. Each output of half-bridges is connected to each of input inductors of the boost to provide the PWM excitation. Using the GSSA model, the synchronous condition and control laws are derived for the amplifier. Properties of the current harmonics in the input inductors are well examined. It is discovered that the dc harmonic, once used to transfer power, is unwanted (parasitic) since it increases conduction loss in switches of the boost. A better idea is to use the fundamental harmonic for power transfer, since it does not create loss in the switches. Complete elimination of the dc current is not feasible for constant frequency operation of the amplifier since the dc current depends on the load coil's resistance. However, significant mitigation of around 55 % is easily achievable. The proposed method improves significantly the efficiency of both the buck pre-regulator and the boost. Synchronous operation is demonstrated in hardware for fixed switching frequency of 480 kHz, power level up to 750 W, input voltage change from 300 V to 600 V, load coil's resistance change of three times, and load coil's inductance change of 3.5 %. Measured efficiency is around 95 %, with a great room for improvements. Chapter five summarizes key contributions and concludes the dissertation.
Ph. D.

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21

Dyachuk, Eduard. "Load diagnostic of power lines to control and optimize the utilization of wind energy." Thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-10090.

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22

Khopkar, Rahul Vijaykumar. "DC-DC converter current source fed naturally commutated brushless DC motor drive." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1257.

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The aim of this work is to reduce the cost and size of a brushless dc motor (BLDC) drive as well as increase the reliability and ruggedness of that drive. Traditional BLDC drives use Voltage Source Inverters (VSI) that utilize hard switching, thereby generating switching losses and entail the use of large heatsinks. VSI needs a huge dc link capacitor that is inherently unreliable and is one of the most expensive components of a drive. Hence, a Current Source Inverter (CSI) is used to replace the hard switchings by natural turn-off, thereby eliminating the heatsinks as well as the large dc link capacitor. A controlled rectifier together with a large inductor act as the current source. The only disadvantage is the large value of the dc link inductor and the huge number of turns needed to achieve these values of the inductances lead to huge resistive losses. Therefore, it is shown that it is possible to replace the controlled rectifier and the large inductor with a suitable dc-dc converter based current source switching at high frequencies and a much smaller value of the dc link inductor. Switching at high frequencies makes it possible to reduce the value of the dc link inductor without increasing the current ripple. Hence, it is possible to have the advantages of using a CSI as well as reduce the value of the dc link inductor without a corresponding increase in the heat sink and snubber requirements.

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Karimi, Seywan. "Dielectrics calculation of on-load tap-changer VUCL." Thesis, KTH, Hållbar produktionsutveckling (ML), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292536.

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This is a bachelor's thesis in Mechanical engineering. The main topic of the thesis is the electrical calculation of the tap changer's shield. Although there are many kinds of tap-changers, this study focuses on VUCL models. The theoretical background of the thesis is that the new shield is suitable and useable in all VUCL models. The primary topic of the thesis is to study that the new shield protects the resistance box in the middle of the tap changers. To do this study, Creo Parametric, Comsol, and SpaceClaim are the programs used.
Detta är en kandidatexamen i maskinteknik. Avhandlingens huvudämne är den elektriska beräkningen av kranbytarens sköld. Även om det finns många olika typer av lindnings fokuserar denna studie på VUCL modeller. Den teoretiska bakgrunden för avhandlingen är att den nya skölden är lämplig och användbar i alla VUCL-modeller. Det primära ämnet för avhandlingen är att studera det nya sköld skyddar motståndet rutan i mitten av lindningskopplare. För att göra denna studie är Creo Parametric, Comsol och SpaceClaim de program som används.

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Suwanasri, Thanapong. "Investigation on no load mechanical endurance and electrical degradation of a circuit breaker model under short circuit current interruption." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979106028.

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25

Pauletti, Luiz Celestino. "Um estudo de uso de gradador de tensão em motores de indução monofásicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/17566.

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O motor de indução é, talvez, o mais robusto e, certamente, um dos motores mais comumente usados. Graças à simplicidade de sua construção, do seu baixo custo, confiabilidade e rendimento relativamente alto com carga nominal é provável que ele permaneça sendo a principal fonte de transformação de energia elétrica em energia mecânica nas aplicações industriais e comerciais por um futuro previsível. O estudo de economia de energia pela redução de perdas é o objetivo do presente estudo. Os motores de indução operam regularmente com fluxo quase constante no entreferro e, portanto, com perdas magnéticas quase constantes. A utilização de um circuito gradador de tensão em série com a alimentação do motor para reduzir o fluxo no entreferro pela redução da tensão aplicada quando a carga não requer fluxo total é o objeto de análise neste estudo. Com a redução da tensão, para manter o conjugado de operação, a velocidade de rotação diminui, ou seja, há um aumento no escorregamento até um valor ótimo para reduzir as perdas totais. Então, esperaria-se que com a redução da tensão aplicada, as perdas magnéticas decresceriam e a eficiência total cresceria. Via de regra, no motor de indução, dada a característica mergulhante de sua curva Conjugado x Velocidade na região em torno da velocidade nominal, o conjugado varia muito mais que a velocidade. Para operação eficiente, a sua tensão aplicada deve ser função da carga que traciona. É objetivo desse trabalho estudar um dispositivo que, colocado em série com a fonte de alimentação de um motor de indução de CA, promove a redução de potência fornecida ao motor, quando a carga aplicada ao motor é menor que a carga nominal. Uma análise da redução da tensão senoidal aplicada através de um auto-transformador de tensão variável é comparada com a redução da tensão através de um circuito gradador baseado em tiristores. A melhor tensão a ser obtida é a que reduz as perdas magnéticas ao mínimo, para cargas que não requerem o fluxo total no entreferro como quando da tensão nominal aplicada. As limitações do processo são estudadas e apresentadas.
The induction motor is perhaps the most rugged, and certainly one of the most commonly used motors. With simply construction, low cost, reliability and efficiency relatively high with rated-load it seems to be a good way to convert electric energy into mechanical energy for industrial and domestic applications for a predictable future. An economy in energy consumption by loss reduction is the goal of this study. The induction motors as normal operate with constant flux in the air-gap and, hence with almost constant losses in the core. The use of a voltage gradador circuit in series with the voltage source applied to the motor for flux reduction in the air-gap by reduction of the voltage when the load do not need full-flux is this study proposal. Hence, with applied voltage reduction, to keep the operational torque, the motor rotation decreases or the slip increases to an optimum value to reduce the total core losses and increase the efficiency. As a rule, the induction motor, by the dip characteristic of the torque x speed curve in the region near the nominal speed, the torque changes much more then the speed. For efficient operation, the applied voltage should be a function of the load. It is the goal or aim of this work to study a device which, when placed in series with the power input of an alternating current induction motor, will produce a reduction in power normally provided to the motor when operated in either a condition where motor loading is less than a rated load. An analysis of voltage ideal sine wave supply reduction applied by an autotransformer with variable voltage is compared with the voltage reduction using a gradador circuit based on thyristors. The optimal voltage operation is the one that decrease the iron losses to minimum, for partial-load that do not need full-flux in the air-gap as when the full voltage is applied. Limitations in the process are investigated and will be showed.

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Kvalheim, Miles R. "Residental Electricity Demand: An Analysis of the Current and Future United States Electricity Grid and Its Impact on Power Consumption." Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/cmc_theses/352.

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The nature of electrical power requires specific infrastructure in order to operate adequately. Currently, the United States electricity grid contains a number of bottlenecking inefficiencies that arise from the aging infrastructure of the system. This paper examines the current state of the United States electricity grid, how potential changes in weather variables can affect the electricity consumption of residential consumers, and how implementation of Smart Grid technology can potentially mitigate these issues. It is determined through regression analysis that each weather variable that was tested proves significant for at least one of the consumers compared. This indicates that there is an enormous magnitude of individual variables that factor into residential electricity consumption and that more efficient and integrated electricity practices are necessary to optimize efficiency.

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27

Ye, Zhihong. "Modeling and Control of Parallel Three-Phase PWM Converters." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29476.

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This dissertation studies modeling and control issues of parallel three-phase pulse-width modulated (PWM) converters. The converters include three-phase boost rectifiers, voltage source inverters, buck rectifiers and current source inverters. The averaging of the parallel converters is performed based on a generic functional switching unit, which is called a phase leg in boost rectifiers and voltage source inverters, and a rail arm in buck rectifiers and current source inverters. Based on phase-leg and rail-arm averaging, the developed models are not only equivalent to the conventional three-phase converter models that are based on phase-to-phase averaging, but they also preserve common-mode information, which is critical in the analysis of the parallel converters. The models reveal such parallel dynamics as reactive power circulation and small-signal interaction. A unique feature of the parallel three-phase converters is a zero-sequence circulating current. This work proposes a novel zero-sequence control concept that uses variable zero-vectors in the space-vector modulation (SVM) of the converters. The control can be implemented within an individual converter and is independent from the other control loops for the converter. Therefore, it greatly facilitates the design and expansion of a parallel system. Proper operation of the parallel converters requires an explicit load-sharing mechanism. In order to have a modular design, a droop method is recommended. Traditionally, however, a droop method has to compromise between voltage regulation and load sharing. After parametric analysis, a novel droop method using a gain-scheduling technique is proposed. The numeric analysis shows that the proposed droop method can achieve both good voltage regulation and good load sharing. An interleaving technique is often used in parallel converter systems in order to reduce current ripples. Because of its symmetrical circuit structure, the parallel three-phase converter system can reduce both differential-mode and common-mode noise with a center-aligned symmetrical SVM. Based on the concept that a symmetrical circuit can reduce common-mode dv/dt noise, a conventional three-phase, four-leg inverter is modified so that its fourth leg is symmetrical to the other three legs. The common-mode dv/dt noise can be practically eliminated with a new modulation strategy. Meanwhile, with a modified control design, the new four-leg inverter still can handle low-frequency common-mode components that occur due to unbalanced and nonlinear load.
Ph. D.

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28

Åkergren, David. "RC Trough Bridges: A Parametric Study using FEM and an Analysis of their Current State." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87260.

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There are approximately 4000 railway bridges in Sweden managed by the Swedish Administration of Transport (Trafikverket), of which a common construction type is the reinforced concrete (RC) trough bridge, which is a structure that consists of a slab carried by two longitudinal main beams which transfer loads towards the supports. A substantial amount of the RC trough bridge population is approaching the end of their service lives which consequently implies that the replacement of some of these bridges can be expected in the near future. Extending their service lives can yield positive effects from a financial- as well as an environmental perspective, and therefore it is highly beneficial to evaluate their capacities as realistically as possible. One factor that may help improve accuracy during the determination of their capacities is an evaluation of how it is affected by the location of the railway track on the bridge. In current design codes defined by Trafikverket, consideration is taken to horizontal track displacement for a minimum displacement of 0.1 m if there doesn’t exist data suggesting that a larger displacement is prevalent on the bridge. However, Trafikverket has received data which suggest that a considerable number of bridges could experience load eccentricities which exceed the standard minimum value. This raises the question whether or not 0.1m is the most optimal limit value for load eccentricity on railway bridges. For RC trough bridges, a larger load eccentricity may result in one main beam carrying a larger portion of the load which will decrease the axle load which the bridge can carry. It is therefore important to evaluate the influence of larger horizontal displacements than what is currently is considered as a preventive action. In addition, several studies on Swedish concrete bridges constructed during the 20th century have pointed to a significant increase in concrete compressive- and tensile strength over time. This suggests that it is possible that a considerable amount of RC trough bridges have a higher capacity than what was originally intended, and further research is required in order to understand the behaviour of these bridges when key material parameters are altered. There are three main tasks which this master thesis seeks to complete. The first part is a detailed analysis of a database named BaTMan (Bridge and Tunnel Management) that belongs to Trafikverket. In this analysis parameters such as span length, age, material type and damages for every identified railway bridge is extracted and further processed in Microsoft Excel in order to gain a clear overview of the RC trough bridge population. The second task regards the development of a non-linear finite element model of a typical RC trough bridge named Lautajokki. The model is analysed using ATENA Science and its behaviour is verified against test results obtained during a full-scale test of the bridge performed by Paulsson et al. (1996). The last task is to use the devolved model to perform a parametric study where the effects of changes in load eccentricity, compressive strength as well as tensile strength is studied.

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Lange, Martin T. "INFLUENCE OF VOLTAGE SOURCE PULSE WIDTH MODULATED SWITCHING AND INDUCTION MOTOR CIRCUIT ON HARMONIC CURRENT CONTENT." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1230942161.

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30

Ahmed, Ismaila Idowu. "The influence of material factors, including cold work, on the susceptibility of stainless steels to stress corrosion cracking." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/the-influence-of-material-factors-including-cold-work-on-the-susceptibility-of-stainless-steels-to-stress-corrosion-cracking(19937317-f1b4-4dbc-ab0e-3eab3760f716).html.

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The main objective of the thesis was to gain better understanding of key parameters associated with Cold Work (CW) and their possible effects on Stress Corrosion Cracking (SCC) susceptibility of Austenitic Stainless Steels (ASS) cold rolled to different degrees. The microstructural characterisation of the cold rolled ASS was carried out using optical microscopy to determine and correlate the average grain size with the level of CW. The assessment of martensite development during the CW was carried out using the neutron diffraction technique. The effects of CW levels and strain paths on the lattice strain evolution during the in-situ loading and on the mechanical failure of cold worked ASS were studied. The electrochemical behaviour of cold rolled ASS was also studied. Finally, The SCC susceptibility of ASS was investigated using the Slow Strain Rate Testing (SSRT) techniques. The post-mortem analyses of the failed samples were carried using the optical and Scanning Electron Microscopy (SEM). The study showed that the average grain size decreases with CW and reaches minimum at 20%CW. The smallest and the largest grain size occurred consistently on the Longitudinal (L) and Short-transverse (S) plane respectively. Evidence of martensite development was only found during the plastic deformation at cryogenic temperature and none was observed at ambient temperature. The study showed that the strength of material increases with the level of CW. The Bauschinger effect occurred when the strain path is reversed and its magnitude is independent on whether the tensile or compressive prestraining comes first or last but rather dependent on the amount of CW. The correlation between the CW levels and the lattice strain evolution during the in-situ loading showed that, the lattice strain increases with prestrain and reaches saturation in the material prestrained to 20%CW.The result of the mechanical failure test showed that, 20% cold rolled material loaded along the L and Transverse (T) directions showed a gradual failure, whilst the material loaded along the S direction exhibited a rapid failure. The SEM micrographs suggest that materials loaded along the L and T direction failed with the characteristic features of pure ductile failure while the specimen loaded along S direction showed mixed features of the ductile and brittle failure. The electrochemical properties of the cold rolled materials are more affected by sample orientation than the levels of CW. The short-transverse plane was observed to be most noble whilst the longitudinal plane was the least noble. The results of the SSRT in the chloride environment showed that the plastic elongation, the ultimate tensile strength and the time to failure decrease as the applied potential increases. The post-mortem analysis of the failed samples with the SEM showed that, the fracture surface contained region of ductile failure characterised by dimples, and region of SCC with secondary cracks along the loading axis. Whilst the cross sectional analysis, showed evidence of predominant transgranular stress corrosion cracks. The study found that SCC susceptibility of the ASS is directly linked to strain heterogeneity and directional anisotropy caused by cold working.

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Rajagopalan, Satish. "Detection of Rotor and Load Faults in BLDC Motors Operating Under Stationary and Non-Stationary Conditions." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11524.

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Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are being increasingly used in critical high performance industries such as appliances, automotive, aerospace, consumer, medical, industrial automation equipment and instrumentation. Fault detection and condition monitoring of BLDC machines is therefore assuming a new importance. The objective of this research is to advance the field of rotor and load fault diagnosis in BLDC machines operating in a variety of operating conditions ranging from constant speed to continuous transient operation. This objective is addressed as three parts in this research. The first part experimentally characterizes the effects of rotor faults in the stator current and voltage of the BLDC motor. This helps in better understanding the behavior of rotor defects in BLDC motors. The second part develops methods to detect faults in loads coupled to BLDC motors by monitoring the stator current. As most BLDC applications involve non-stationary operating conditions, the diagnosis of rotor faults in non-stationary conditions forms the third and most important part of this research. Several signal processing techniques are reviewed to analyze non-stationary signals. Three new algorithms are proposed that can track and detect rotor faults in non-stationary or transient current signals.

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32

Bjurelid, Martin, and Emran Murina. "Analys & kartläggning av Uddevalla citys mellanspänningsnät." Thesis, Högskolan Väst, Avdelningen för data-, elektro- och lantmäteriteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-8291.

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Kraven på ett driftsäkert elnät ökar hela tiden i takt med att elanvändning blir allt viktigare i dagens samhälle. Luftledningar byts ut med markkabel och möjlighet till reservmatningar samt bra elkvalitet är av hög prioritering. Skicket på elnätets utrustning försämras med åren och kommer med tiden behöva bytas ut. Med uppdrag från Uddevalla Energi AB har siffror tagits fram berörande spänningsfall, kapacitiv jordfelsström och belastningar vid normaldrift och reservmatning, samt ålder och typ på kablar i Uddevalla citys mellanspänningsnät. Den här rapporten presenterar dessa resultat och ger några förslag på ändringar om så krävs. Även en del om planerade framtida utbyggnationer tas upp och hur dessa påverkar nätet. För att få fram resultaten används Uddevalla Energis program för nätberäkning, "DpPower". Beräkningarna visade att vid normaldrift var alla värden godkända enligt tumregler som Uddevalla Energi följer. Vid reservmatning däremot var vissa linjer överbelastade, analysen visar dock tillgängliga lösningar. Ålder och status på kablar i nätet varierar stort vilket gör det svårt att specificera hur ombyggnationer ska ske. Hänsyn bör istället tas till överbelastningar.
The demand of reliable power distribution is increasing as the usage of power is increasing in the society of today. Overhead lines are replaced by underground cables, availability to reserve power supply and power quality is of high priority. The condition of the equipment deteriorates over the years and will eventually have to be replaced. By request from Uddevalla Energi, values have been provided concerning voltage drop, capacitive ground fault current and loads during normal operation and standby power supply. The types and ages of cables in Uddevalla City’s high-voltage network has also been looked at. This report presents these results and gives some suggestions for modifications if required. Planned future deployments are looked over and how these may affect the network. To obtain these results the network calculating program "DpPower" was used. The calculations presented shows that in normal operation all values are approved within the company standards that Uddevalla Energi follows. For the reserve supply however, some lines are overloaded. The analysis shows possible solutions for these issues. Age and status of cables in the network varies widely, making it difficult to specify how redevelopments should take place. Instead the overloads should be given more consideration.

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33

Barakati, Amir. "Dynamic interactions of electromagnetic and mechanical fields in electrically conductive anisotropic composites." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3562.

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Анотація:

Recent advances in manufacturing of multifunctional materials have provided opportunities to develop structures that possess superior mechanical properties with other concurrent capabilities such as sensing, self-healing, electromagnetic and heat functionality. The idea is to fabricate components that can integrate multiple capabilities in order to develop lighter and more efficient structures. In this regard, due to their combined structural and electrical functionalities, electrically conductive carbon fiber reinforced polymer (CFRP) matrix composites have been used in a wide variety of applications in most of which they are exposed to unwanted impact-like mechanical loads. Experimental data have suggested that the application of an electromagnetic field at the moment of the impact can significantly reduce the damage in CFRP composites. However, the observations still need to be investigated carefully for practical applications. Furthermore, as the nature of the interactions between the electro-magneto-thermo-mechanical fields is very complicated, no analytical solutions can be found in the literature for the problem. In the present thesis, the effects of coupling between the electromagnetic and mechanical fields in electrically conductive anisotropic composite plates are studied. In particular, carbon fiber polymer matrix (CFRP) composites subjected to an impact-like mechanical load, pulsed electric current, and immersed in the magnetic field of constant magnitude are considered. The analysis is based on simultaneous solving of the system of nonlinear partial differential equations, including equations of motion and Maxwell's equations. Physics-based hypotheses for electro-magneto-mechanical coupling in transversely isotropic composite plates and dimension reduction solution procedures for the nonlinear system of the governing equations have been used to reduce the three-dimensional system to a two-dimensional (2D) form. A numerical solution procedure for the resulting 2D nonlinear mixed system of hyperbolic and parabolic partial differential equations has been developed, which consists of a sequential application of time and spatial integrations and quasilinearization. Extensive computational analysis of the response of the CFRP composite plates subjected to concurrent applications of different electromagnetic and mechanical loads has been conducted. The results of this work verify the results of the previous experimental studies on the subject and yield some suggestions for the characteristics of the electromagnetic load to create an optimum impact response of the composite.

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Húsek, Jan. "Dvoukvadrantový spínaný proudový zdroj pro buzení cívek." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-218879.

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This master`s thesis deals with design and realization of two-quadrant switching current source for inductive loads. Output current adjustable range is 0 – 1A. Selected topology enables change of current direction. Current supply is made with TDA8920 integrated circuit. Thesis also contains basic information about switching supplies and coils.

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Rangel, Camilo Alberto Sepúlveda. "Modelo aproximado de sistemas de distribuição considerando geração distribuida e o efeito da tensão na carga." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/127892.

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Esta dissertação apresenta um modelo aproximado de rede desenvolvido para análise de sistemas de distribuição em regime permanente. O modelo é detalhado do ponto de vista matemático e teórico considerando a representação dos elementos em derivação da rede (cargas e geradores) e dos limites operacionais empregando aproximações lineares. A modelagem linear permite determinar de forma simples os valores das tensões e correntes do sistema, podendo ser empregada em problemas de otimização relacionados ao planejamento e expansão de sistemas de distribuição. A representação da carga considera a influência da variação da tensão, fator determinante nas redes de distribuição. Também é considerada a inclusão de geração distribuída (GD) sendo implementada para diferentes modos de operação, permitindo ainda a minimização das perdas para a barra onde a GD está alocada. Para validar a abordagem proposta, os resultados do modelo apresentado foram comparados em termos de tensões, correntes e perdas com resultados obtidos com o modelo convencional de fluxo de carga, solucionado pelo algoritmo de varredura. Os testes foram realizados em dois sistemas de distribuição conhecidos, um de 70 barras e um de 135 barras. Para o sistema de 70 barras foi avaliado o uso de diferentes modos de operação da GD. Finalmente, para o sistema de 135 barras foram comparados os resultados do modelo proposto com o fluxo de carga convencional caracterizando a GD como uma barra de tensão controlada (PV) para diversos valores de injeção ativa na barra selecionada. As conclusões confirmam a validade e as vantagens que o modelo desenvolvido neste trabalho proporciona.
This work presents an approximate model developed to the analysis of electrical distribution systems at steady state. Both mathematical and theoretical details are given considering the representation of the shunt elements (loads and generators) and the operating limits of the network, using linear approximations. The linear modeling adopted resulted in a simple way to determine the values of the voltages and currents of the system; further the model can be applied to optimization problems related to optimal operation and expansion planning of distribution systems. The load representation considers the influence of voltage variations, which play an important role in the distribution networks. This work also considers the inclusion of distributed generation (DG), which is assessed under several modes of operation, including one mode which allows to minimize the losses at the node where the DG is located. To validate the proposed approach, the results for two example networks, given in terms of voltages, currents and losses, were compared with corresponding results obtained with conventional load flow model, solved by the backward-forward sweep method. The examples networks used to test and validate the model are known distribution systems, one having 70 and the other 135 nodes. Regarding the system with 70 nodes, the inclusion of DG was studied for several operational modes. Finally, the system of 135 nodes were used to compare the results of the proposed model with the results of the conventional load flow; in this case, the GD was characterized as a controlled-voltage bar (PV) for various levels of active power injection into the bar where the GD is located. The conclusions show the validity and advantages of the proposed model.

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Цибуля, Ю. А. "Техніко-економічні умови приєднання СЕС «Нерафа» до електроенергетичної системи". Thesis, Чернігів, 2021. http://ir.stu.cn.ua/123456789/25268.

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Цибуля, Ю. А. Техніко-економічні умови приєднання СЕС «Нерафа» до електроенергетичної системи : випускна кваліфікаційна робота : 141 "Електроенеретика, електротехніка та електромеханіка" / Ю. А. Цибуля ; керівник роботи В. М. Бодунов ; НУ "Чернігівська політехніка", кафедра електричної інженерії та інформаційно-вимірювальних технологій. – Чернігів, 2021. – 107 с.
Об’єкт проєктування – сонячна електростанція встановленою потужністю 10 МВт. Мета роботи – забезпечення якості та надійності видачі генеруючої потужності сонячної електростанції в електричну мережу АТ «ЧЕРНІГІВОБЛЕНЕРГО». В даному проєкті запропоновано шляхи приєднання сонячної електростанції до електричних мереж АТ «ЧЕРНІГІВОБЛЕНЕРГО». Виконано вибір обладнання для сонячної електростанції, запропоновано схему збору потужності сонячної електростанції, виконано розрахунок та оцінку параметрів режимів роботи сонячної електростанції та вплив нової сонячної електростанції на параметри режимів роботи мереж АТ «ЧЕРНІГІВОБЛЕНЕРГО». Виконано розрахунок економічної ефективності прийнятих технічних рішень.
The object of design is a solar power plant with an installed capacity of 10 MW. The purpose of the work is to ensure the quality and reliability of the power generation of the solar power plant in the electric network of JSC «CHERNIGIVOBLENERGO». This project proposes ways to connect the solar power plant to the electrical networks of JSC «CHERNIGIVOBLENERGO». The choice of equipment for the solar power plant was made, the scheme of solar power plant collection was proposed, the calculation and estimation of the parameters of the solar power plant operation modes and the influence of the new solar power plant on the operation parameters of JSC «CHERNIGIVOBLENERGO» were performed. The calculation of economic efficiency of the accepted technical decisions is executed.

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Luedtke, Elin. "Minimizing Transformer No-Load Losses at Hydropower Plants : A Study of Effects from Transformer Switch-Off During Stand-by Operation." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447635.

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Hydropower is the most important power balancing resource in the Swedish electrical power system, regulating the power supply to match the load. Consequently, several hydropower plants have periods of stand-by operation where the power production is absent but where several devices within a plant are still active. Such a device is the step-up power transformer, which during stand-by operation still generates no-load energy losses. These losses can accumulate to a considerable amount of energy and costs during the long technical lifetime of the apparatus. One option to minimize these no-load energy losses is by turning the transformer off when its generating unit is in stand-by operation. However, when this transformer operational change has been explained to experts in the field, the most common response has been that a more frequent reenergizing of a transformer leads to higher risks for errors or transformer breakdowns. This study aimed to analytically investigate three effects from this operational change. First, the potential of fatigue failure for the windings due to the increased sequences of inrush current. Secondly, the thermal cycling as a consequence of change in present losses. Lastly, the energy and economic saving potentials for hydropower plants where this operational adjustment is applied. The study used both established as well as analytical tools explicitly created for this study. These were then applied on currently active transformers in different plant categories in Fortum’s hydropower fleet. The study primarily showed three things. Firstly, risk of fatigue failure due to the increased presence of inrush currents did not affect the transformer’s technical lifetime. Secondly, the thermal cycling changes were slightly larger with absent no-load losses during stand-by operation. The average temperature for the transformer decreased, which in general is seen as a positive indicator for a longer insulation lifetime and thus the transformer’s technical lifetime. Finally, the created frameworks showed the potential of saving energy and money for all plant categories, where the potential grew with the installed production capacity and the stand-by operation timeshare. Despite the simplifications made to describe the complex reality of a transformer operating in a hydropower plant, this thesis contributes to lay a foundation for future investigation of an easy adjustment to avoid unnecessary energy losses and costs for transformers in hydropower plants.

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Blengini, Neto Adolfo. "Ambiente multim?todos para otimiza??o de opera??es em sistemas de distribui??o de energia el?trica generalizados." Pontif?cia Universidade Cat?lica de Campinas, 2017. http://tede.bibliotecadigital.puc-campinas.edu.br:8080/jspui/handle/tede/926.

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Анотація:

Submitted by SBI Biblioteca Digital (sbi.bibliotecadigital@puc-campinas.edu.br) on 2017-03-23T14:50:03Z No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5)
Made available in DSpace on 2017-03-23T14:50:03Z (GMT). No. of bitstreams: 1 ADOLFO BLENGINI NETO.pdf: 3955942 bytes, checksum: 45ddc01c026b2c6b88359672fba01257 (MD5) Previous issue date: 2017-02-16
Pontif?cia Universidade Cat?lica de Campinas ? PUC Campinas
This study proposes the development of an environment for optimization of the operations of electrical distribution systems. The environment is proposed for the modern electrical distribution networks considering the possibility of inclusion of distributed generation and mesh topology. The environment is divided into three modules. The first module consists of standardizing the input and organization data of the network in memory using techniques of object-oriented software engineering. This approach simplifies the processes of nodal analysis of the circuits, improves the performance of the solution and allows reusing the objects and operations in other implementations. The second module is responsible for analyzing and represents network characteristics: topology, load model and distributed generation points. The third consists of the BFS, FW and OCF methods to perform the current flow calculation and allows the user to choose the desired algorithm, being able to present the currents and voltages in each iteration. The choice of different methods in the optimization environment allows the use of the most adherent method to the different network topologies, the types of load, the flexibility in the use of capacity constraints of the elements of the network and the inclusion of generation limits and voltage limits. In order to verify the adhesion and the efficiency of the environment, simulations were carried out on balanced three-phase circuits of primary distribution of 11, 33 and 400 buses with different load models, radial or mesh topology, with and without distributed generation.
Esta pesquisa prop?e-se ao desenvolvimento de um ambiente para otimiza??o da opera??o de sistemas de distribui??o de energia. O ambiente ? aderente ?s modernas redes de distribui??o de energia por considerar a possibilidade de inclus?o de gera??o distribu?da e topologia em malha. O ambiente est? dividido em tr?s m?dulos. O primeiro m?dulo consiste na padroniza??o dos dados de entrada e organiza??o da rede em mem?ria no formato de grafo utilizando t?cnicas de engenharia de software orientada a objetos. Este enfoque simplifica os processos de an?lises nodais dos circuitos, melhora o desempenho da solu??o e permite reaproveitar os objetos e opera??es em outras implementa??es. O segundo m?dulo ? respons?vel pela an?lise e representa??o das caracter?sticas da rede: topologia, modelo de cargas e pontos de gera??o distribu?da. O terceiro consiste dos m?todos BFS, FW e OCF para a execu??o do c?lculo do fluxo de corrente e d? a op??o ao usu?rio de escolha do enfoque desejado, podendo apresentar as correntes e tens?es em cada itera??o. A op??o de escolha de diferentes m?todos no ambiente de otimiza??o possibilita o uso do m?todo mais aderentes ?s diferentes topologias de rede, aos tipos modelos de carga, a flexibilidade no uso de restri??es de capacidade dos elementos da rede e a inclus?o de limites de gera??o e limites de tens?o. Com a finalidade de comprovar a ader?ncia e efici?ncia do ambiente foram realizadas simula??es em circuitos trif?sicos equilibrados de distribui??o prim?ria com 11, 33 e 400 barras com modelos de carga constante, topologia radial, anel, com e sem gera??o distribu?da.

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Blanchet, Floria. "Analyse et caractérisation des performances en puissance de transistors bipolaires à hétéro-jonction SiGe:C pour des applications de radiocommunications portables." Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/f1bfd25b-e0f7-4e43-859b-0d7d3b984d33/blobholder:0/2007LIMO4018.pdf.

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Ces travaux portent sur la caractérisation de transistors de puissance bipolaires à hétéro-jonction Si/SiGe:C, issus des fonderies de STMicroelectronics Crolles, destinés aux applications de radiocommunications mobiles. Un historique des principales évolutions technologiques du transistor bipolaire est proposé. Les simulations CW, utilisant le modèle HICUM, ont mis en évidence l’influence du point de polarisation et des impédances de charge sur l’optimisation en rendement. Les simulations 2-tons et multi-tons ont confirmé le compromis rendement/linéarité. Une résolution originale pour tester la robustesse des transistors est ensuite exposée. Puis, les mesures réalisées sur le banc load-pull actif du laboratoire Xlim ont montré une bonne cohérence avec les simulations CW. Les comparaisons 2-tons sont prometteuses. Enfin, cette thèse a permis d’identifier le problème d’étalonnage du banc load-pull passif de STMicroelectonics. La résolution proposée a été approuvée par Focus Microwaves
This work deals with the characterization of power hetero-junction bipolar transistors Si/SiGe:C produced by STMicroelectronics Crolles foundry, destined to mobile radio-communications applications. A historic of the main technological evolutions of the bipolar transistor is proposed. The CW simulations, using the HICUM model, highlighted the influence of the biasing and the charge impedances on the efficiency optimization. Next, an original resolution to test the transistors robustness is presented. Then, the measurements realized on the active load-pull bench of the Xlim laboratory showed a good consistency with the CW simulations. The 2-tons comparisons are promising. Finally, this thesis lets to identify a calibration problem on the passive load-pull bench of the STMicroelectronics laboratory. The proposed resolution has been approved by Focus Microwaves

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40

Rapant, Jaromír. "Rekonstrukce nosné ocelové konstrukce dvoupodlažního objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226071.

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his thesis deals with exploration of paper mill building, structural load, and assessment of current load bearing structure and proposing reconstruction. Bearing structure is entirely made out of steel and it’s done as XYZ frame. The building is located in Olsany u Sumperka, this defines the climate. The paper mill is of a platform of 54,0 x 48,25 m. It’s a two floor building with average height of 13,22m. Thesis contains foto documentation of the building and tests of strength of the steel in the bearing structure. Small statistical calculation was done, of all current elements of the steel structure. And necessary reconstruction was based on these calculations.

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Перетятко, Павло Олександрович, та Peretiatko Pavlo. "Проектування системи освітлення та електропостачання Полтавського краєзнавчого музею імені Василя Кричевського". Master's thesis, Тернопільський національний технічний університет імені Івана Пулюя, кафедра електричної інженерії,Тернопіль, Україна, 2020. http://elartu.tntu.edu.ua/handle/lib/33482.

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Анотація:

У формуванні історичної пам’яті та національної ідентичності музейні заклади відіграють важливу роль. Основне призначення музеїв полягає в збереженні культурно-історичних, природних, наукових цінностей, а також поширення знань через вивчення і демонстрацію пам’яток та експонатів. При демонстрації музейних експонатів, як і будь-яких інших об’єктів, одну із найважливіших ролей відіграє освітлення, яке саме і визначає зорові відчуття, які є першим етапом естетичного сприйняття навколишнього простору в музейному приміщенні. Правильно підібрана освітлювальна система може відразу задовольняти вимоги щодо безпеки, надійності та економічності, а коректно організоване освітлення є одним з основних факторів отримання комфортних умов для ефективного функціонування зорового апарату спостерігача.
В роботі запропоновано систему освітлення та її електропостачання для приміщень виставкового, адміністративного та допоміжного призначень будівлі краєзнавчого музею із загальною площею приміщень 4873,70 м2
The qualification work proposes a lighting system and its power supply for the premises of the exhibition, administrative and auxiliary purposes of the building of the Museum of Local Lore with a total area of 4873.70 m2.
ВСТУП 6 1. Аналітичний розділ 8 1.1. Аналіз характеристик приміщень будівлі музею 8 1.2. Аналіз основних функціональних вимог до освітлення музейних приміщень 10 1.3. Аналіз нормативних вимог до освітлення приміщень музейних будівель 13 1.4. Висновки до розділу 19 2. ПРОЕКТНО-КОНСТРУКТОРСЬКИЙ РОЗДІЛ 20 2.1. Вибір виду і системи освітлення та нормованих значень освітленості приміщень будівлі музею 20 2.2. Вибір джерел світла та світлових приладів для освітлення музейних приміщень 23 2.3. Вибір напруги, джерела живлення, марки проводу електричної освітлювальної мережі музею 28 2.4. Електротехнічний розрахунок електричної освітлювальної мережі музею 32 2.4.1. Розрахунок електричної освітлювальної мережі музею на мінімум провідникового матеріалу 33 2.4.2. Розрахунок електричної освітлювальної мережі по струму навантаження та вибір апаратів захисту 42 2.5. Висновки до розділу 45 3 РОЗРАХУНКОВО-ДОСЛІДНИЦЬКИЙ РОЗДІЛ 46 3.1. Світлотехнічний розрахунок системи освітлення музею 46 3.2. Моделювання освітлювальної установки музею в пакеті DIALux 50 3.3 Розрахунок питомого енергоспоживання системою освітлення приміщень краєзнавчого музею 58 5 3.4. Висновки до розділу 60 4. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 62 4.1. Аналіз факторів на об'єкті проектування, які впливають на наслідки уражень електричним струмом 62 4.2. Причини виникнення пожеж та основні шляхи їх запобігання в музейних приміщеннях 65 ЗАГАЛЬНІ ВИСНОВКИ ПЕРЕЛІК ПОСИЛАНЬ 68 70 ДОДАТОК А 74

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42

Svoboda, Ondřej. "Návrh elektrizace jednokolejné trati." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-400599.

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The main topic of the thesis is the design of single-track electrification of a direct current system of 3 kV and an alternating current system of 5 kV 50 Hz and then economically evaluate it over a period of 30 years. The work deals with basic traction systems and also deals with the calculation of main parameters of electric trains. The thesis describes in detail the procedure for the design of the electrification of the track and a partial introduction to the simulation programs that were used for energy calculations.

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43

Goyal, Sachin. "Power network in the loop : subsystem testing using a switching amplifier." Queensland University of Technology, 2009. http://eprints.qut.edu.au/26521/.

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Анотація:

“Hardware in the Loop” (HIL) testing is widely used in the automotive industry. The sophisticated electronic control units used for vehicle control are usually tested and evaluated using HIL-simulations. The HIL increases the degree of realistic testing of any system. Moreover, it helps in designing the structure and control of the system under test so that it works effectively in the situations that will be encountered in the system. Due to the size and the complexity of interaction within a power network, most research is based on pure simulation. To validate the performance of physical generator or protection system, most testing is constrained to very simple power network. This research, however, examines a method to test power system hardware within a complex virtual environment using the concept of the HIL. The HIL testing for electronic control units and power systems protection device can be easily performed at signal level. But performance of power systems equipments, such as distributed generation systems can not be evaluated at signal level using HIL testing. The HIL testing for power systems equipments is termed here as ‘Power Network in the Loop’ (PNIL). PNIL testing can only be performed at power level and requires a power amplifier that can amplify the simulation signal to the power level. A power network is divided in two parts. One part represents the Power Network Under Test (PNUT) and the other part represents the rest of the complex network. The complex network is simulated in real time simulator (RTS) while the PNUT is connected to the Voltage Source Converter (VSC) based power amplifier. Two way interaction between the simulator and amplifier is performed using analog to digital (A/D) and digital to analog (D/A) converters. The power amplifier amplifies the current or voltage signal of simulator to the power level and establishes the power level interaction between RTS and PNUT. In the first part of this thesis, design and control of a VSC based power amplifier that can amplify a broadband voltage signal is presented. A new Hybrid Discontinuous Control method is proposed for the amplifier. This amplifier can be used for several power systems applications. In the first part of the thesis, use of this amplifier in DSTATCOM and UPS applications are presented. In the later part of this thesis the solution of network in the loop testing with the help of this amplifier is reported. The experimental setup for PNIL testing is built in the laboratory of Queensland University of Technology and the feasibility of PNIL testing has been evaluated using the experimental studies. In the last section of this thesis a universal load with power regenerative capability is designed. This universal load is used to test the DG system using PNIL concepts. This thesis is composed of published/submitted papers that form the chapters in this dissertation. Each paper has been published or submitted during the period of candidature. Chapter 1 integrates all the papers to provide a coherent view of wide bandwidth switching amplifier and its used in different power systems applications specially for the solution of power systems testing using PNIL.

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44

Cardoso, Renato Tavares. "Método de carga para banco de baterias em fontes ininterruptas de energia que busca garantir o estado de carga completa: corrente pulsada modificado." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/8576.

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Анотація:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This Master s Dissertation is proposes the development of a charge management system of a bank of 16 lead-acid batteries with 7Ah load capacity, commonly used in Uninterruptible Power Supplies (UPS). This system aims to ensure that these batteries reach a full charge status faster than the conventional way. To this, it was chosen to make the modification of the pulsed current charging method, in order to reduce problems, such as elevation of bus voltage to return the energy to it, or dissipation of that energy in a resistance, resulting in lower system efficiency, inherent in the method taken as a basis when the battery power withdrawal interval occurs. For the development of the suggested charging system the static converter Full-Bridge Isolated with modulation Phase Shift was chosen. To implement the digital control as well as its practical development in the same laboratory the simplified modeling of this converter was made. The results of simulation and experimental to validate the method are presented.
Esta dissertação de mestrado tem como proposta o desenvolvimento de um sistema de gerenciamento de carga de um banco de 16 baterias de chumbo ácido, com capacidade de carga de 7Ah, comumente utilizado em Fontes Ininterruptas de Energia (UPS). Este sistema visa garantir que estas baterias cheguem a um estado de carga completo e de forma mais rápida que a convencional. Para isto, foi escolhido fazer a modificação do método de carga de corrente pulsada, com o objetivo de reduzir problemas inerentes do método tomado como base, quando ocorre o intervalo de retirada de energia da bateria, tais como: elevação da tensão do barramento ao retornar a energia para ele, ou, dissipar esta energia em uma resistência, o que acarreta em baixa eficiência do sistema. Para o desenvolvimento do sistema de carga sugerido foi escolhido o conversor estático Full-Bridge Isolado com modulação Phase Shift. Foi feita a modelagem simplificada deste conversor, para a implementação do controle digital, assim como o desenvolvimento prático do mesmo em laboratório. São apresentados os resultados de simulação e experimentais para validar o método.

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45

Starý, Zdeněk. "Model pro výpočet oteplovacích charakteristik silových kabelů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217817.

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The result of this assignment is the Model for the Cable Thermal Characteristic Calculation. Firstly, there is a prepared overview that is focused on the essential ideas of cable technology. The following part describes the simple possibilities of passaging the heat. Secondly,the physical essence of warming cables as well as the possibility to discover the methods how to calculate the warming cables are also mentioned in this task.There is an opportunity to find the methods for calculating the warming cables as well. The model was verificationed in the conclusion of my assignment. The measurement was done and the empirical results were compared with the results that were achieved by modeling.

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46

"Load Sharing Low Dropout Regulators Using Accurate Current Sensing." Master's thesis, 2017. http://hdl.handle.net/2286/R.I.46344.

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abstract: The growing demand for high performance and power hungry portable electronic devices has resulted in alarmingly serious thermal concerns in recent times. The power management system of such devices has thus become increasingly more vital. An integral component of this system is a Low-Dropout Regulator (LDO) which inherently generates a low-noise power supply. Such power supplies are crucial for noise sensitive analog blocks like analog-to-digital converters, phase locked loops, radio-frequency circuits, etc. At higher output power however, a single LDO suffers from increased heat dissipation leading to thermal issues. This research presents a novel approach to equally and accurately share a large output load current across multiple parallel LDOs to spread the dissipated heat uniformly. The proposed techniques to achieve a high load sharing accuracy of 1% include an innovative fully-integrated accurate current sensing technique based on Dynamic Element Matching and an integrator based servo loop with a low offset feedback amplifier. A novel compensation scheme based on a switched capacitor resistor is referenced to address the high 2A output current specification per LDO across an output voltage range of 1V to 3V. The presented scheme also reduces stringent requirements on off-chip board traces and number of off-chip components thereby making it suitable for portable hand-held systems. The proposed approach can theoretically be extended to any number of parallel LDOs increasing the output current range extensively. The designed load sharing LDO features fast transient response for a low quiescent current consumption of 300µA with a power-supply rejection of 60.7dB at DC. The proposed load sharing technique is verified through extensive simulations for various sources and ranges of mismatch across process, voltage and temperature.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2017

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47

Chang, Kuei-Hui, and 張貴輝. "Power Factor Improvement with Load-Current Injection for Motor Drives." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/8t829m.

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碩士
國立臺北科技大學
電力電子產業研發碩士專班
102
The purpose of this thesis is to build a single phase BOOST type Power Factor Corrector in order to a speed control system of a SRM motor driver. The front stage employs a single-phase boost type AC/DC converter, which provides the inverter stage with steady DC voltage. Then, a SRM motor is driven by the inverter to accomplish the motion control. The AC-DC converter control the perfect duty of power switch, so that the low-distortion and high-power-factor line current is obtained. The controller consists of current, voltage loop and load-current injection with parameters determined through Bode plot method. The model of the proposed system has been established and simulated by Matlab/PSIM. The system is implemented by the digital signal processor (TMS320F2812). This controller supplies pulse-width modulation signals to the power switches of PFC stages, and handles the PWM command and feedback current and voltage signal. Both the simulation and experimental results are obtained to show the proposed system. The specifications of a single-phase boost type PFC include: input voltage = 110±15%, output voltage = 200 V, and maximum output power = 600W. The single phase BOOST type PFC is implemented using the TI DSP (TMS320F2812) .Experimental results show that the power factor reaches 0.9 under full load condition and efficiency is up to 96% as input voltage varied.

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48

Wu, Chun-Chieh, and 吳俊傑. "Analysis of Circulating Current for Distribution Feeders during Load Transfer." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/03568243732651492001.

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碩士
國立海洋大學
電機工程學系
91
As the load demand grows, providing steady supply of electric energy has become a long-term goal of power utilities. In the distribution system, feeders are usually switched during load transfer for sakes of system operation and maintenance. In order to keep the power quality, the task of feeder switching needs to be performed without interrupting the supply of electricity, resulting in some related problems. Due to differences in voltages and phases between two feeders, circulating current comes into existence. A large amount of circulating current during load transfer may cause the protective relay to malfunction to trip the distribution feeders, and then to interrupt the supply of electricity. This thesis is to study some related problems about the switching of distribution feeders for load transfer. The static condenser and on load tap changer of transformers will be considered for reducing the voltage difference between two feeders. Moreover, some strategies are also investigated for preventing the protective relaying system to malfunction during load transfer.

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49

Banerjee, Debmalya. "Load Commutated SCR Current Source Inverter Fed Induction Motor Drive With Sinusoidal Motor Voltage And Current." Thesis, 2008. http://hdl.handle.net/2005/744.

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This thesis deals with modeling, simulation and implementation of Load Commutated SCR based current source Inverter (LCI) fed squirrel cage induction motor drive with sinusoidal voltage and sinusoidal current. In the proposed system, the induction motor is fed by an LCI. A three level diode clamped voltage source inverter (VSI) is connected at the motor terminal with ac chokes connected in series with it. The VSI currents are controlled in such a manner that it injects the reactive current demanded by the induction motor and the LCI for successful commutation of the SCRs in the LCI. Additionally, it absorbs the harmonic frequency currents to ensure that the induction motor draws sinusoidal current. As a result, the nature of the motor terminal voltage is also sinusoidal. The concept of load commutation of the SCRs in the LCI feeding an induction motor load is explained with necessary waveforms and phasor diagrams. The necessity of reactive compensation by the active filter connected at the motor terminal for the load commutation of the thyristors, is elaborated with the help of analytical equations and phasor diagrams. The requirement of harmonic compensation by the same active filter to achieve sinusoidal motor current and motor voltage, is also described. Finally, to achieve the aforementioned induction motor drive, the VA ratings of the active filter (VSI) and the CSI with respect to VA rating of the motor, are determined theoretically. The proposed drive scheme is simulated under idealized condition. Simulation results show good steady state and dynamic response of the drive system. Load commutation of the SCRs in the LCI and the sinusoidal profile of motor current and voltage, have been demonstrated. As in LCI fed synchronous motor drives, a special mode of operation is required to run up the induction motor from standstill. As the SCRs of the LCI are load commutated, they need motor terminal voltages for commutation. At standstill these voltages are zero. So, a starting strategy has been proposed and adopted to start the motor with the aid of the current controlled VSI to accelerate until the motor terminal voltages are high enough for the commutation of the SCRs in the LCI. The proposed drive is implemented on an experimental setup in the laboratory. The IGBT based three level diode clamped VSI has been fabricated following the design of the standard module in the laboratory. A generalized digital control platform is also developed using a TMS320F2407A DSP. Two, three phase thyristor bridges with necessary firing pulse circuits have been used as the phase controlled rectifier and the LCI respectively. Appropriate protection scheme for such a drive is developed and adopted to operate the drive. Relevant experimental results are presented. They are observed to be in good agreement with the simulation results. The effect of capacitors connected at the output of the LCI in the commutation process of the SCRs in the LCI is studied and analyzed. From the analysis, it is understood that the capacitors form a parallel resonating pair with filter inductor and the motor leakage inductance, which results in an undesired oscillation in the terminal voltage during each of the commutation intervals leading to commutation failure. So, in the final system, the capacitors are removed to eliminate any chance of commutation failure of the SCRs in the LCI. It is shown by experiment that the commutation of the SCRs takes place reliably in the absence of the capacitors also. The commutation process is studied and analyzed without the capacitors to understand the motor terminal voltage waveform of the experimental results.

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50

Chiu, Ting-Sung, and 邱定松. "A Novel Design and Implementation of Current-Controlled Electronic Load Simulators." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/48318997266367855850.

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Анотація:

碩士
國立成功大學
電機工程學系
89
In the burn-in test of power electronic equipment, the load simulator is very useful for the evaluation of their operation performance. This motivates the design and implementation electronic load simulators proposed in this thesis. With the designated current-controlled technology, the proposed simulator can emulate the behaviors of different types of loads that includes resistive load, inductive load, capacitive load, and rectified load. In addition, this proposed system owns the ability of energy-recovering that ensures injecting the energy of high power-factor and low harmonics form back to the utility. In this way, energy consumption can be significantly reduced, while the investment cost can be lowered down considerably. This method was tested under various scenarios. From experimental results, they have demonstrated the feasibility of the method for load simulation applications, thereby revealing the suitability and potential for electric power quality applications.

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