Dissertations / Theses: 'Electric machinery'

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Wang, Rong-Jie. "Design aspects and optimisation of an axial field permanent magnet machine with an ironless stator." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53351.

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Thesis (PhDEng)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: The advent of new high energy product permanent magnet materials has opened great opportunities for novel electrical machine topologies with advantageous features such as high efficiency and high power/weight ratio. Amongst others, axial field permanent magnet (AFPM) machines with ironless stators are increasingly being used in power generation applications. Because of the absence of the core losses, a generator with this type of design can operate at a substantially high efficiency. Besides, the high compactness and disc-shaped profile make this type of machine particularly suitable for compact integrated power generation systems. Due to construction problems, the generator application of this type of machine has been limited to quite a low power range. There is a need to investigate the performance capability of this type of AFPM machine in the upper medium power level. The focus of this thesis is on the design optimisation of the air-cooled AFPM generator with an ironless stator. A design approach that directly incorporates the finite element field solution in a multi-dimensional optimisation procedure is developed and applied to the design optimisation of a 300 kW (at unity power factor) AFPM generator. To enable an overall design optimisation of the machine, different design aspects, such as the cooling capacity, the mechanical strength and eddy loss, are also studied in this research. To enable the free movement of the rotor mesh with respect to the stator mesh, the air-gap element originally proposed by Razek et. al. is derived for Cartesian coordinate systems. For minimising the large computation overhead associated with this macro element, a number of existing time-saving schemes have been utilised together with the derived Cartesian air-gap element. The developed finite element time-step model is applied to calculating the steadystate performance of the AFPM machine. Since the flux distribution in an AFPM machine is three dimensional by nature, calculating the eddy current loss by merely using a simple analytical method may be subject to a significant error. To overcome this problem, the two dimensional finite element field modelling is introduced to perform accurate field analysis. To exploit the full advantages of the twodimensional finite element modelling, a multi-layer approach is proposed, which takes into account the variation of the air-gap flux density in the conductors with regard to their relative positions in the air-gap. To account for the radial variation of the field, a multi-slice finite element modelling scheme is devised. The thermal analysis is an important aspect of the design optimisation of AFPM machines. From a design point of view, it is preferable to have a simple but effective method for cooling analysis and design, which can easily be adapted to a wide range of AFPM machines. In this thesis a thermofluid model of the AFPM machine is developed. The fluid flow model is needed for calculating the air flow rate, which is then used to find the convective heat transfer coefficients. These are important parameters in the subsequent thermal calculations. Experimental investigations have been carried out to verify each of the above-mentioned models/methods. With these models implemented, the design optimisation of an air-cooled ironless stator 300 kW (at unity power factor) AFPM generator is carried out. The performance measurements done on the fabricated prototype are compared in this thesis with predicted results. The study shows that the proposed design approach can be applied with success to optimise the design of the AFPM machine. The advantages of high power density, high efficiency, no cogging torque and good voltage regulation make this type of AFPM machine very suitable for power generator applications. The optimum steady-state performance of the AFPM machine shows that this machine with an ironless stator is an excellent candidate for high speed power generator applications, even in the upper medium power level. The good cooling capacity of this type of machine holds the promise of its being a self-cooled generator at high power ratings.
AFRIKAANSE OPSOMMING: Die uitvinding van nuwe hoë energiedigtheid permanent magneet materiale het groot geleenthede vir nuwe elektriese masjien topologië laat ontstaan met voordelige eienskappe soos hoë benuttingsgraad en hoë drywing/gewig verhouding. Onder andere word die aksiaalveld permanente magneet (AVPM) masjiene met kernlose stators toenemend gebruik vir elektriese generator toepassings. As gevolg van die afwesigheid van kernverliese kan 'n generator met hierdie tipe ontwerp teen 'n aansienlik hoë benuttingsgraad werk. Daarbenewens maak die hoë kompaktheid en skyfvorm-profiel die masjien in besonder geskik vir die ontwikkeling van kompak geïntegreerde drywing generator stelsels. As gevolg van konstruksie probleme is die toepassing van hierdie tipe masjien as generator beperk tot redelik lae drywingsgebiede. Dit is nodig om die werkverrigtingsvermoë van hierdie tipe AVPM masjien in die boonste medium drywingsgebied te ondersoek. Die fokus van hierdie tesis is op die ontwerp-optimering van 'n lugverkoelde AVPM generator met 'n kernlose stator. 'n Ontwerpsbenadering wat die eindige element veldoplossing in 'n multi-dimensionele optimeringsprosedure insluit, is ontwikkel en toegepas op die ontwerpsoptimering van 'n 300 kW (by eenheidsarbeidsfaktor) AVPM generator. Om 'n globale ontwerpsoptimering van die masjien te kan doen is verskillende ontwerpsaspekte soos die verkoelingskapasiteit, meganiese sterkte en werwelverliese ook in hierdie navorsing bestudeer. Om die vrye beweging van die rotormaas ten opsigte van die statormaas te verseker is die lugspleet-element, soos oorspronklik deur Razek et al voorgestel, afgelei vir Cartesiaanse koórdinaat stelsels. Om die lang berekeningstyd geassosieer met hierdie makro-element te minimaliseer is 'n aantal bestaande tydbesparende metodes saam met die ontwikkelde Cartesiaanse lugspleet-element gebruik. Die ontwikkelde eindige element tydstapmodel is toegepas om die bestendige werkverrigting van die AVPM masjien te bereken. Aangesien die vloedverspreiding in 'n AVPM masjien van nature drie-dimensioneel is, kan die berekening van die werwelstroomverliese tot aansienlike foute lei as eenvoudige analitiese metodes gebruik word. Om hierdie probleem te oorkom is twee-dimensionele eindige element modellering gebruik om akkurate veld-analise te doen. Om die volle voordele van die twee- dimensionele eindige element modellering te eksploiteer is 'n multi-laag benadering voorgestel wat die variasie van die lugspleetvloeddigtheid in die geleiers met betrekking tot hulle relatiewe lugspleetposisies in ag neem. Om voorsiening te maak vir die radiale variasie van die veld, is 'n multi-skyf eindige element modelleringstegniek ontwikkel. Die termiese analise is 'n belangrike aspek van die ontwerpsoptimering van AVPM masjiene. Vanuit 'n ontwerpsoogpunt is dit verkieslik om 'n eenvoudige maar tog effektiewe metode van verkoelingsanalise en -ontwerp te hê wat maklik toegepas kan word op 'n wye reeks van AVPM masjiene. In hierdie tesis word 'n termovloeimodel van die AVPM masjien ontwikkel. Hierdie vloeimodel is nodig vir die berekening van die lugvloeitempo, wat op sy beurt weer nodig is om die konveksie hitte-oordrag koëffisiënte te bepaal. Hierdie is belangrike parameters in die opvolgende termiese berekeninge. Eksperimentele ondersoek is uitgevoer om elkeen van die bogenoemde modelle en metodes te verifieer. Nadat hierdie modelle geïmplimenteer is, is die ontwerpsoptimering van 'n 300 kW (by eenheidsarbeidsfaktor) lugverkoelde kernlose stator AVPM generator uitgevoer. Die werkverrigtingmetings gedoen op 'n vervaardigde prototipe masjien, word in hierdie tesis vergelyk met voorspelde resultate. Daar word getoon dat die voorgestelde ontwerpsbenadering met sukses toegepas kan word om die ontwerp van die AVPM masjien te optimeer. Die voordele van hoë drywingsdigtheid, hoë benuttingsgraad, geen vertandingsdraaimomente en goeie spanningsregulasie maak hierdie masjien baie aantreklik vir generator toepassings. Die optimum bestendige werkverrigting van die AVPM masjien toon dat hierdie masjien met 'n kernlose stator 'n goeie kandidaat is vir hoë spoed generator toepassings, selfs in die boonste medium drywingsgebied. Die goeie verkoelingskapasiteit van hierdie tipe masjien hou die belofte in van'n selfverkoelde generator by hoë drywing aanslae.

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Cash, M. Alex. "Detection of turn faults arising from insulation failure in the stator windings of AC machines." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15460.

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Burns, Angela D. "Comparison of two electrofishing gears (backpack and parallel wires) and abundances of fishes of the upper Greenbrier River drainage." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5165.

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Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains vii, 65 p. : ill., maps (part col.). Includes abstract. Includes bibliographical references.

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Lemmer, Edward Charles. "Wind-electric pump system design." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2527.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
The aim of this study is to analyse the operation of a wind-electric pumping system (WEPS) as an alternative to conventional mechanical wind pumps for application in stand-alone water-pumping schemes. The steady-state as well as the dynamic operation of such a system is analysed. Through these analyses, practical guidelines are given in the design and sizing of the different system components to ensure efficient and reliable operation. Theoretical analyses are supported by measured results conducted on a small scale wind-electric pump system. The limitations involved in the design and implementation of a large scale wind-electric pump system are presented through a case study. It is firstly concluded that small-scale wind-electric pump systems have the potential of offering superior performance and flexibility to conventional mechanical wind pumps. It is secondly concluded that large-scale wind-electric pump systems are best suited, in terms of economic and practical feasibility, to pumping applications with low pressures and medium to high wind regimes at the turbine installation site.

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Hu, Jiangang. "Sensorless control of AC machines for integrated starter generator application." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196258873.

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Stack, Jason R. "Fault signature detection for rolling element bearings in electric machines." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13276.

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Zhang, Hui. "On Electric Machinery for Integrated Motor Drives in Automotive Applications." Doctoral thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207942.

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Compact, electric drives for automotive traction applications represent animportant enabler towards realizing tomorrow’s fossil free transport solutions.One attractive solution is to integrate the power electronic converter withits associated electric machinery into a single unit. This thesis, along withits appended papers, considers design and analysis of electric machinery forintegrated electric drives intended for automotive applications. Particular focusis put on permanent-magnet synchronous machines (PMSMs) with interiormountedpermanent magnets combined with modular converter topologies.In the first part of the thesis, different converter concepts and windingarrangements suitable for an integrated drive are reviewed. Compared to theconventional solution utilizing a three-phase two-level converter, a compactintegration can be implemented by physically splitting the converter and itsassociated dc-link capacitor into a number of converter submodules. Moreover,a modular concept also enables a certain level of fault tolerance.In the second part of the thesis, fractional-slot concentrated windings(FSCWs) are analyzed. First, a review for how to determine suitable slot, pole,and phase combinations is identified considering mainly the winding factor forthe main harmonic and the associated rotor losses. Then, integrated modularconverter concepts and associated winding configurations are considered andslot, pole and phase combinations that also comply with the consideredmodular converters are proposed. Further, two possible winding arrangementssuitable for the stacked polyphase bridges (SPB) and the parallel polyphasebridges (PPB) type converter are compared with respect to torque duringpost-fault operation in the event of failure of a single converter submodule.In the third part, an iterative process adopting both finite element analysisand analytical techniques is proposed for the design of PMSMs with interiormountedpermanent magnets and FSCWs. The resulting machine designsillustrate tradeoffs in terms of fault tolerance, power factor, torque density,and potential for field-weakening operation. From a given set of specifications,an experimental prototype is also designed and built.Finally, since a FSCW generally results in a large harmonic content ofthe resulting flux-density waveform, models for predicting eddy-current lossesin the permanent magnets are analyzed and compared. Particularly, modelsadopting different formulations to the Helmholtz equation to solve for the eddycurrents are compared to a simpler model relying on an assumed eddy-currentdistribution. Boundaries in terms of magnet dimensions and angular frequencyare also identified in order to aid the machine designer whether the mostsimple loss model is applicable or not. With a prediction of the eddy-currentlosses in the permanent magnets together with a corresponding thermal model,predicted volumetric loss densities exemplified for combinations of slot andpole numbers common in automotive applications are presented along withthe associated thermal impact.

QC 20170530

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Qin, Ling. "A permanent-magnet switched-flux generator." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3210935.

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Ramsey, Jack S. "Shipboard applications of non-intrusive load monitoring." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1475.

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Sachdeva, Rajesh. "Two-phase flow through electric submersible pumps /." Access abstract and link to full text, 1988. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9021070.

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Liu, Guoping. "Oscillation monitoring system based on wide area phasor measurements in power systems." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Summer2010/g_liu_060110.pdf.

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Thesis (Ph. D.)--Washington State University, August 2010.
Title from PDF title page (viewed on July 23, 2010). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 76-81).

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Nel, Wynand. "Impact of pole shape and proportions on flux leakage in switched-flux generators." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433347.

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Tang, Yun-chung. "Motor simulation and parameter identification in a reciprocating mechanism." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10312009-020104/.

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Opperman, Adriaan Jacobus. "Analysis of factors influencing the performance of a hydrokinetic coil pump." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1021041.

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A hydrokinetic coil pump (HCP) is described by its name. It is a coil pump driven by the kinetic energy in flowing water. The hydrokinetic energy is converted into mechanical energy by means of a paddle-wheel. The coil pump makes up part of the paddle-wheel and together is called a HCP. The HCP floats in a stream of flowing water while tethered to the bank. The focus of the study was to identify and analyse the factors influencing the HCP. The HCP was then optimized for rural application. Data acquisition took place through experimentation on a full scale experimental platform according to a central composite experimental design. Variables used for the experimentation included; Stream Velocity, Delivery Head, Number of Coils, Discharge, Number of Paddles, Paddle-Wheel rotational speed Overall HCP efficiencies of up to 22 percent were obtained. The efficiency would drop as the stream velocity increased. Stream velocity has been identified as the most influential factor with regards to the variables analysed by this study. The HCP is ideal for rural application. The simplicity of the design ensures reliability as well as an effective water supply solution. The HCP is ideal for slow flowing rivers and can deliver up to 1190ℓ/h to a delivery head of 5m with a stream velocity of 1.2m/s. This is sufficient to supply a small rural community with running water.

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O'Leary, Beth Andrews. "Analysis of high-speed rotating systems using Timoshenko beam theory in conjunction with the transfer matrix method /." Online version of thesis, 1989. http://hdl.handle.net/1850/10608.

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Liles, Howard J. "High throughput profile millling for the flexible and accelerated processing of electric steels." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47628.

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The proliferation of electric machines has drastically increased in recent years and is likely to increase into the future. This interest in the production of advanced, high power density electrical machines that are small in size has heightened the need for flexible manufacturing processes to produce their laminated components during short batch and prototyping production runs. A means of cost effective, accelerated prototyping of these machines will have a substantial impact on their design and optimization, reducing time requirements to produce and test a given design. A review of the current manufacturing methods for prototyping electric machines was conducted. In particular, laser cutting, electric discharge machining, and abrasive waterjet (AWJ) machining were researched as competitive processes. Each of these methods exhibits marked advantages and disadvantages that present the opportunity for a new process to compete. This work investigates the applicability of high throughput profile milling (HTPM) for the prototyping of advanced electric machines, specifically, the process parameter space for milling of electrical steels. The material response will be determined by characterizing its specific cutting energy and utilizing this to develop a model to predict cutting forces during the milling process. Optimal process parameters will be investigated to obtain maximum productivity and minimal burr formation. Finally, the impact of HTPM processing on the magnetic properties of electrical steels will be compared to that of a leading prototyping technology, AWJ machining.

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Li, Chiamin. "CRM and the use of internet in Electric & Machinery industry-TECO." Thesis, University of Gävle, Department of Technology and Built Environment, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-6356.

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Everyone already knows what the customer relationship management is and it has been improved and managed by the internet, called electronic customer relationship management. The information technology, such as the internet, is making it easier for customers and industries. The purpose of this study is to analyze the customer relationship management in TECO Electric & Machinery Co.,Ltd. and how this could be improved via the internet with four research questions. Additionally, the primary information was conducted by a face-to-face interview with the managing director who has empirical experiences in that field and qualitative approach was utilized. The theories about the customer characteristic, customer involvement, the future customer relationship management, and the use of internet were used. In TECO, the main customer characteristics are financially attractive customers and the customer in a close relationship and the customers usually involved in the development stage of new product development processes. For the future orientation, TECO may be able to pay attention on people-driven application and take Amazon as an example in the use of the internet. Moreover, the probability of further research was discussed in this study.

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Opgenoorth, Andreas, Stefan Quabeck, Doncker Rik W. De, and Katharina Schmitz. "Challenges and possibilities of the integration of electric drives in mobile machinery." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71118.

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This paper provides an overview of the challenges and possibilities of the integration of electric drives into diesel-hydraulic excavators. Due to the drivers of emission reduction, the use of renewable energies and more energy efficient systems, a global push leads to the integration of electric drives in excavators. In mobile machinery such as excavators, new possibilities and challenges of the adaptation of the drive train and energy storage arise. Rotational actuators can be powered by direct electric drives to avoid losses of the hydraulic system. Adapted hydraulic system topologies enable recuperation and reduce throttling losses in hydraulic systems. Variable and overall higher electric motor speeds reduce the size of the electric and hydraulic components and enable operation in more efficient operating points. To evaluate possible changes to the traditional hydraulic excavator systems, a simulation model is built and the proposed adaptations are implemented. The paper concludes with the evaluation of the proposed system changes and an outlook for further possibilities of hydraulic system adaptions in relation to the electric drive.

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McGilp, Malcolm. "An integrated design environment for electric machines." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/9023/.

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In this essay I describe an original and sustained contribution to the methodology of research and design of electric machines, during a period of fundamental change in the technology itself; from pen and paper methods of design to a wholly computer-based methodology. This is paralleled by an even more dramatic transformation in analytical and numerical methods in engineering. The technological changes have arisen mainly in the growth of electronics, in connection with variable speed drives but also in new magnet and other materials. The SPEED (Scottish Power Electronics and Electric Drives) Laboratory was founded in 1986 by Professor TJE Miller, to promote knowledge transfer between the University of Glasgow and a consortium of companies from the electric machine industry. A symbiotic relationship between Professor Miller and the author has arisen in the development of what the Laboratory is now principally known for: the SPEED software. In establishing this group, Professor Miller brought an international reputation in electrical machines theory and experience in writing FORTRAN programs for calculating the characteristics of motors. On joining the Laboratory in 1987, alongside a basic knowledge of motors, I brought a more specialised capacity in software design and development. This complementarity of roles and expertise has been a significant factor in the success of subsequent development over 27 years, enabling us to achieve more than either would have been able to do individually. My major contributions are summarized as follows: 1. Initial implementation of the software: making the necessary engineering compromises and development to shoe-horn the code within the constraints of the early PC platform. This was a significant milestone in the genesis of SPEED. As the PC was becoming cheap and therefore ubiquitous, this direction enabled me to put design for electric machines ii on the desktop of every engineer in the consortium, numbering over 1500 in 2011. 2. The hardware and software platform of the PC has evolved at a rapid pace since the early development outlined above. My ongoing research and development has progressed in parallel enabling the SPEED software to grow into a software suite rather than functioning as individual programs. At each stage I have extended the capabilities and sophistication of the software while retaining the key attributes of speed and cost-effectiveness. 3. Contribution to research within the University of Glasgow through support of PhD and post-doctoral work and in the general research community through contributions to a wide range of technical papers as listed in the references of this essay.

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Hurst, Kevin D. "Transducerless control and monitoring of induction machines by detection of magnetic saliency harmonics." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15713.

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Miri, Seyed-Mehdi. "Modeling and fault detection in electromagnetic devices : applications to synchronous machines and signal conditioning systems /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487332636476273.

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Lee, Seungkoo. "An architecture for a diagnostic/prognostic system with rough set feature selection and diagnostic decision fusion capabilities." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/14715.

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Smuts, Johan L. (Johan Leodolf). "Critical evaluation of a position sensorless control technique for the reluctance synchronous machine drive." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/70135.

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Thesis (MScEng)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: The aim of this study is to critically evaluate the voltage injection position sensorless control technique as applied to the reluctance synchronous machine (RSM) drive and to implement the technique on a 5.5 kW RSM and a 110 kW RSM. The technique is evaluated by using an accurate mathematical model of the RSM in a simulation package, called Simuwin. The negative effects that cross-magnetisation and the slotted air-gap have on the technique are intensively investigated. It was showed that these effects can cause an error in the position estimation of up to 30°. The TMS320F240 DSP was used as the controller for the RSM drives to implement the position sensorless control technique. Measurements on both RSM drives confirm the simulated results.
AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om die spannings-injeksie posisie sensorlose beheer tegniek soos toegepas op die reluktansie sinchroon masjien (RSM) aandryfstelsel, krities te evalueer en te implementeer op 'n 5.5 kW RSM en op 'n 110 kW RSM. Die tegniek is geevalueer deur 'n akkurate wiskundige model van die RSM saam te stel en die model te gebruik in 'n simulasie pakket, genaamd Simuwin. Daar is veral klem gele op die negatiewe invloed wat kruis-magnetisering en 'n gegleufde lug-spleet op die tegniek het. Dit is bewys dat hierdie eienskappe van die RSM 'n fout in die posisie afskatting van tot 30° kan veroorsaak. Die TMS320F240 DSP is gebruik as beheerder vir die RSM aandryfstelsels om sodoende posisie sensorlose beheer op altwee masjiene toe te pas. Metings op albei stelsels bevestig die simulasies.

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Link, Rainer. "Innovative approaches to recycling of small and electric motors from end-of-life vehicles, electric bicycles and industrial machinery." Thesis, KTH, Industriell ekologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190181.

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Recycling and recovery of materials and energy from waste is a key factor to mitigate virgin material demands and reduce resource consumption by utilising waste as a resource for new products. However, some critical materials, such as neodymium, are barely recycled because of missing information on amount and disposition of these critical materials within the waste streams. The goal of the study is to quantify recycling potentials from small and electric motors originating from end-of-life vehicles (ELV), electric bicycles and industrial machinery in Germany and the EU with focus on currently lost rare earth elements. Furthermore, innovative approaches to improve recycling of these motors shall be investigated. Therefore, a calculation model to predict current and future waste streams and the incorporated recycling potentials has been developed. The results show an increasing trend of recycling potentials from small and electric motors for all waste streams. The recycling potential of neodymium is estimated at a range of 150 t to 240 t in 2020 in Germany. However, data inaccuracy and the calculation model are likely to cause overestimation of actually available recycling potential and have to be interpreted carefully. In conclusion, disassembly of small and electric motors from ELV and electric bicycles in combination with a subsequent specific recycling process has been identified as promising to improve utilisation of the recycling potentials of rare earth elements from small and electric motors. However, in case recycling quotas are the prior goal of improvement, the application and further optimisation of post shredder technology is more relevant.

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Merabet, Adel. "Commande non linéaire à modèle prédictif pour une machine asynchrone /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2007. http://theses.uqac.ca.

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Thèse (D.Eng.) -- Université du Québec à Chicoutimi, 2007.
La p. de t. porte en outre: Thèse présentée à l'Université du Québec à Chicoutimi comme exigence partielle du doctorat en ingénierie. Bibliogr.: f. 169-181. Document électronique également accessible en format PDF. CaQQUQ

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Siyambalapitiya, Don Joseph Tilak. "Investigation of cage rotor variables including on-line monitoring." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237745.

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Jurkiewicz, David J. (David James). "Modular machinery arrangement and its impact in early-stage naval electric ship design." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74922.

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Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-77).
Electrical power demands for naval surface combatants are projected to rise with the development of increasingly complex and power intensive combat systems. This trend also coincides with the need of achieving maximum fuel efficiency at both high and low hull speeds. A proposed solution to meet current and future energy needs of conventionally powered naval surface combatants is through the use of an Integrated Power System (IPS), which is seen as the next evolution in naval ship design. Unfortunately, historically-based ship design process models and parametrics cannot accommodate new-concept designs that are not incremental changes to previous practice. Additionally, integrating IPS with the next generation of ship designs is also synonymous with the desire of conducting system-level tradeoffs early within the ship design process. In an effort to enhance the relationship between new-concept designs and historically-based ship design processes, this thesis focuses on a novel approach of incorporating IPS at the earliest stage of the design process as part of assessing system-level tradeoffs early. This thesis describes a methodology for the system design and arrangement of an IPS machinery plant based on an objective of meeting a desired power generation level, effectively introducing a power constraint at the start of the design process. In conjunction with the methodology development, a hierarchical process and design tool for integration with Graphics Research Corporation's (GRC) naval architecture software suite, Paramarine, is also produced to assist in rapid development and evaluation of various IPS arrangements. The result of this process, through several case studies, provides insight into equipment selection philosophy, the initial sizing of the ship's machinery box, and the initial definition of electrical zones. Lastly, the developed tool is also used to aid in the creation of "design banks," allowing the naval architect to manage weight, power, and volume at the beginning of the ship design process; therefore, supporting early system-level tradeoffs for new-concept designs.
by David J. Jurkiewicz.
S.M.
S.M.in Naval Architecture and Marine Engineering

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Hosseinpour, Amir. "An investigation into electric supercharging for emission reduction by means of engine downsizing." Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/19787/.

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This thesis describes an investigation into the operation and performance of internal combustion engines boosted by an electric supercharger (eSC) in combination with a turbocharger. Engine downsizing offers one of the most effective ways to meet increasingly demanding CO2 reduction targets set for the automotive vehicles. The addition of a turbocharger has enabled significant downsizing but the loss of torque at low engine speeds remains a key barrier to further downsizing. A known solution to this problem is to additionally boost the engine using a supercharger. However, until recently, this was very difficult to implement economically on engines with modest engine power suitable for small to medium sized vehicles due to the low air mass flow rates for such engines. Now, a new turbo-machinery innovation, the high forward swept TurboClaw compressor, allows significant boosting to be done at low flow rates yet with moderate compressor shaft speeds. Since this compressor can be driven at a moderate speeds, the electric motor which drives for the electric supercharger (eSC) is more affordable. The research objective was to assess this new eSC system be means of a theoretical and experimental investigation. There are two possible combinations in terms of whether the (eSC) goes before the turbocharger (ETC), or after (TEC). Employing the eSC after turbocharger generally has the advantage of broadening the eSC map, towards higher-mass flows since a denser air exits the turbo-compressor as the turbocharger provides boosted air to the system. This augments the overlap of the two operating maps for the two devices. However the real benefit of eSC in each layout depends on the engine (baseline). In this research ETC and TEC produce basically the same torque increase; the real eSC benefit is at low speed where the nominal maximum torque is recovered for all the range. However since the current drawn from the battery is a key factor for this application, the investigation shows that the thermodynamic power requested by eSC is less than 1.5kW for ETC layout while this value is 2.5kW for TEC layout. Therefore ETC layout was chosen as the final configure to be implemented on the selected vehicle for the dyno test purposes since it requires less power. Theoretical models for the engine, turbocharger and TurboClaw eSC including electric motor were created and validated. The system of all components was designed including control system and strategy. A key result showed that the eSC was found to boost the torque of a 1.0 litre turbocharged engine by 125% and 58% for 1000 rpm and 1200 rpm respectively.

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Lee, Sang-Bin. "Sensorless stator winding temperature estimation for induction machines." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14719.

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Baggu, Murali Mohan. "Advanced control techniques for doubly fed induction generator-based wind turbine converters to improve low voltage ride-through during system imbalances." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Baggu_09007dcc806684bd.pdf.

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Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 27, 2009) Includes bibliographical references (p. 126-130).

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Riley, Caryn M. "Current-based sensorless vibration monitoring of small ac machines." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13741.

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32

Halligan, Gary. "Fault detection and prediction with application to rotating machinery." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Halligan_09007dcc80708356.pdf.

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Thesis (M.S.)--Missouri University of Science and Technology, 2009.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 25, 2009) Includes bibliographical references.

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Merchant, Richard W. "Recursive estimation using the bilinear operator with applications to synchronous machine parameter identification /." Title page, contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phm5543.pdf.

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34

Abrahams, Leon Gary. "Computerised speed monitoring system for nylon spinning." Thesis, Peninsula Technikon, 1996. http://hdl.handle.net/20.500.11838/1123.

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Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town,1996
The Southern Nylon Spinning plant, at South African Nylon Spinners in Bellville - Cape Town - South Africa, is one of the oldest on the site and a need arose to upgrade the existing method used in speed monitoring in this particular plant. This system was unable to produce alarms on speed limits being exceeded (i.e. on under-speed or over-speed). There was no alarm logging or historical trending. Manual records on speed were either incomplete or non-existent. Thus the purpose of this study was to investigate the existing speed monitoring system and implement a suitable computerised method of speed monitoring.

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So, Ting-pat Albert. "PWM-based asymmetrical rotor synchronous/industion drive /." [Hong Kong : University of Hong Kong], 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12359452.

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36

Lawler, Clinton T. "A two-phase spherical electric machine for generating rotating uniform magnetic fields." Thesis, Monterey, California. Naval Postgraduate School, 2007. http://hdl.handle.net/10945/2995.

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This thesis describes the design and construction of a novel two-phase spherical electric machine that generates rotating uniform magnetic fields, known as a fluxball machine. Alternative methods for producing uniform magnetic fields with air-cored solenoidal magnets are discussed and evaluated. Analytical and numerical models of these alternatives are described and compared. The design details of material selection, slot geometry, and mechanical connections are described for the fluxball machine. The electrical properties of the machine are predicted and measured. Based on these properties, two modes of operation for the fluxball machine, normal and resonant, are described, and reference tables of important operating parameters are given. The drive and measurement circuitry for the fluxball machine are described. The magnetic properties of the fluxball machine are measured using Hall effect sensors. The calibration of two different Hall effect sensors is performed, providing the ability to measure the magnetic fields accurately to +or- 1%. Measurements of the magnetic field in the uniform field region are taken and compared with predicted values. The attenuation and distortion of the magnetic fields due to diffusion through the inner fluxball winding is measured as a function of operating frequency. Finally, future uses of this machine for various applications are discussed.
Contract number: N62271-97-G-0026
US Navy (USN) author.

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Sitsha, Lizo M. M. "Design of tapered and straight stator pole switched reluctance machines." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51678.

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Thesis (MEng)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: This thesis deals with the design and optimisation of medium power traction switched reluctance machines with tapered and straight stator poles. Only the prototype of the tapered stator pole machine is constructed and evaluated in this study. A non-commercial finite element package is used in the design and optimisation of the machines. The finite element method is applied directly in the optimisation procedure to optimise the design of the machines in multi-dimensions. The lumped circuit analysis method is used only for the purpose of verifying some of the finite element calculated. It is not used in the optimisation procedure. The performance characteristics of the tapered and straight stator pole machines are compared and discussed and the tapered stator pole machine is found to have better torque performance. Also the calculated and measured static torque versus rotor position characteristics of the tapered stator pole machine are compared and discussed.
AFRIKAANSE OPSOMMING: Die tesis beskryf die ontwerp en optimering van medium drywing trekkrag geskakelde reluktansie masjiene met tapse en reguit stator pole. Slegs 'n prototipe van die tapse stator pool masjien is gebou en geëvalueer. Die masjiene is ontwerp en geoptimeer met behulp van 'n nie-kommersiële eindige element metode pakket. Die eindige element metode is direk in die optimerings algoritme gebruik vir die optimering van die masjiene in multi-dimensies. Die gekonsentreede parameter stroombaananalise is slegs gebruik om sommige van die eindige element berekenings te verifeer. Die vermoës van die tapse en reguit stator pool masjiene is vergelyk en bespreek. Die resultate toon dat die tapse stator pool masjien se draaimoment vermoë beter is as die van die reguit stator pool masjien. Die berekende en gemete statiese draaimoment teenoor rotorposisie van die tapse stator pool masjien is ook vergelyk en bespreek.

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38

Duan, Yao. "Method for design and optimization of surface mount permanent magnet machines and induction machines." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37280.

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Advances in electrical machinery with high efficiencies could significantly reduce the cost of industrial and residential energy systems, thereby reducing fossil fuel needs and emissions. Electrical machine design is a comprehensive process based on several factors, including economic factors, material limitations, specifications and special application-dependent factors. At the same time, machine design is a multi-physics task comprising of electric design, magnetic design, insulation design, thermal design and mechanical design. However, the out-of-date conventional machine design can neither reflect the advances in the past 30 years, nor exploit the trade-offs between design factors from the multi-physics nature of the electrical machine. This work focus on the development a fast and efficient method for the design and optimization of Surface Mount Permanent Magnet (SMPM) machines and induction machines, as influenced by the energy source, mechanical loads, thermal effects, and the up-to-date developments in materials and manufacturing capabilities. A new analytical design method is developed for the electromagnetic design of SMPM machines. Both distributed and concentrated winding types of SMPM machines are considered and compared. Based on the proposed electromagnetic analytical design method and a generic thermo-mechanical machine design model [1], an innovative and computationally efficient electromagnetic-thermo-mechanical integrated design method is developed for SMPM machines. Particle Swarm Optimization (PSO) is applied in a novel way based on this integrated design method for the multi-objective design optimization of SMPM machines. With the proposed method, the thermal and mechanical design is no longer treated separately and heuristically as in the traditional design, but has been systemically integrated with the electromagnetic design; the effect of power source, cooling capability, thermal limits, and up-to-date material capabilities are also reflected in the design and optimization. Superior designs compared to traditional designs can be achieved with PSO based multi-objective optimization. The proposed integrated design approach also has the merit of good computational efficiency and provides a significant time reduction of the design cycle compared to finite element analysis. A novel electromagnetic analytical design method of induction machines has been developed, which needs only six prime design variables but is able to design induction machines in fine details. The advantage over the traditional and other existing design method is that this proposed method does not have the heuristic selection of the design variables and does not need manual design iterations. The computing time is almost negligible and the design cycle is significantly reduced compared to the tradition machine design.

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Wai, Lo-kau. "Microprocessor-based field-oriented control of a synchronous motor drive using a three-phase solid-state sinusoidal current source /." Hong Kong : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12434425.

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40

Peqquena, Suni Juan Carlos. "Sobre a determinação de parametros de geradores sincronos para estudos de comportamento dinamico de sistemas eletricos." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258997.

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Orientador: Ernesto Ruppert Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-15T03:55:20Z (GMT). No. of bitstreams: 1 PeqquenaSuni_JuanCarlos_M.pdf: 1533933 bytes, checksum: dbd348c759114d83f69069e35635591c (MD5) Previous issue date: 2009
Resumo: Os parâmetros do modelo matemático dinâmico dos geradores síncronos como a resistência elétrica dos enrolamentos de estator por fase, a resistência elétrica do enrolamento de campo, as resistências elétricas dos enrolamentos amortecedores de eixo direto e de eixo em quadratura, as reatâncias de dispersão dos enrolamentos de estator por fase, do enrolamento de campo e dos enrolamentos amortecedores, bem como as reatâncias de magnetização de eixo direto e de eixo em quadratura do gerador são possíveis de serem determinadas, com razoável aproximação, através de ensaios específicos como o ensaio para determinação da reatância de Potier, o ensaio de curto-circuito trifásico brusco e os ensaios de rejeição de carga. Neste trabalho discute-se o problema da determinação de parâmetros do gerador síncrono auxiliado pela realização de simulações dinâmicas usando o software Matlab/Simulink e a sua biblioteca SimPowerSystems para determinação de parâmetros de um gerador de pólos lisos e de um gerador de pólos salientes através de ensaios de medição da reatância síncrona de eixo direto, ensaio de Potier, ensaio de curto-circuito brusco e ensaio de rejeição de carga. Diversos resultados e conclusões são apresentados usando os parâmetros padronizados mostrados explicitamente por Krause em seu importante livro publicado em 1986. Trata-se de um trabalho que tem finalidades didática e tecnológica de discutir essa questão
Abstract: The synchronous generator dynamic mathematical model parameters like the per phase stator winding electrical resistance, the field winding resistance, the direct and quadrature damping winding resistances, the field winding leakage reactance, the per phase stator winding leakage reactance, the damping winding leakage reactances, and direct and quadrature magnetizing reactances are possible to be determined with some accuracy through specific tests like the Potier reactance determination, the sudden short-circuit test and the load rejection tests. This work is addressed to the problem of salient poles and cylincrical rotor synchronous generator parameters determination aided by the use of dynamic simulations implemented with the Matlab/Simulink package using its SimPowerSystems library. Some results and conclusions about the parameters determination are presented using the standardized and fundamental parameters as shown in the Krause book published in 1986. This paper has both didactic and technological subjects and it is addressed to discuss several aspects on the real parameters determination activities
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica

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41

韋盧溝 and Lo-kau Wai. "Microprocessor-based field-oriented control of a synchronous motor drive using a three-phase solid-state sinusoidal current source." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31208940.

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42

Seyoum, Dawit Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "The dynamic analysis and control of a self-excited induction generator driven by a wind turbine." Awarded by:University of New South Wales. School of Electrical Engineering & Telecommunications, 2003. http://handle.unsw.edu.au/1959.4/22008.

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This thesis covers the analysis, dynamic modelling and control of an isolated selfexcited induction generator (SEIG) driven by a variable speed wind turbine. The voltage build up process of an isolated induction generator excited by AC capacitors starts from charge in the capacitors or from a remnant magnetic field in the core. A similar voltage build up is obtained when the isolated induction generator is excited using an inverter/rectifier system with a single DC capacitor on the DC link of the converter. In this type of excitation the voltage build up starts from a small DC voltage in the DC link and is implemented using vector control. The dynamic voltage, current, power and frequency developed by the induction generator have been analysed, simulated and verified experimentally for the loaded and unloaded conditions while the speed was varied or kept constant. Results which are inaccessible in the experimental setup have been predicted using the simulation algorithm. To model the self excited induction generator accurate values of the parameters of the induction machine are required. A detailed analysis for the parameter determination of induction machines using a fast data acquisition technique and a DSP system has been investigated. A novel analysis and model of a self-excited induction generator that takes iron loss into account is presented in a simplified and understandable way. The use of the variation in magnetising inductance with voltage leads to an accurate prediction of whether or not self-excitation will occur in a SEIG for various capacitance values and speeds in both the loaded and unloaded cases. The characteristics of magnetising inductance, Lm, with respect to the rms induced stator voltage or magnetising current determines the regions of stable operation as well as the minimum generated voltage without loss of self-excitation. In the SEIG, the frequency of the generated voltage depends on the speed of the prime mover as well as the condition of the load. With the speed of the prime mover of an isolated SEIG constant, an increased load causes the magnitude of the generated voltage and frequency to decrease. This is due to a drop in the speed of the rotating magnetic field. When the speed of the prime mover drops with load then the decrease in voltage and frequency will be greater than for the case where the speed is held constant. Dynamic simulation studies shows that increasing the capacitance value can compensate for the voltage drop due to loading, but the drop in frequency can be compensated only by increasing the speed of the rotor. In vector control of the SEIG, the reference flux linkage varies according to the variation in rotor speed. The problems associated with the estimation of stator flux linkage using integration are investigated and an improved estimation of flux linkage is developed that compensates for the integration error. Analysis of the three-axes to two-axes transformation and its application in the measurement of rms current, rms voltage, active power and power factor from data obtained in only one set of measurements taken at a single instant of time is discussed. It is also shown that from measurements taken at two consecutive instants in time the frequency of the three-phase AC power supply can be evaluated. The three-axes to twoaxes transformation tool simplifies the calculation of the electrical quantities.

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43

Lee, Yongsik. "A study of parametric excitation applied to a MEMS tuning fork gyroscoe." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4697.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 29, 2007 Vita. Includes bibliographical references.

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44

Wung, Peter Yu-Pu. "Operating point dependent modeling of synchronous reluctance motors and its implication on vector controlled motor performance." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15042.

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Brown, Daniel F. Jr. "Single crystal piezoelectric pumping using displacement amplification." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/19124.

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So, Ting-pat Albert, and 蘇廷弼. "PWM-based asymmetrical rotor synchronous/industion drive." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31208903.

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47

Cheng, Siwei. "Utilizing the connected power electronic converter for improved condition monitoring of induction motors and claw-pole generators." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43638.

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This dissertation proposes several simple, robust, and non-intrusive condition monitoring methods for induction motors fed by closed-loop inverters and claw-pole generators with built-in rectifiers. While the flexible energy forms synthesized by power electronic converters greatly enhance the performance and expand the operating region of induction motors and claw-pole generators, they also significantly alter the fault behavior of these electric machines and complicate the fault detection and protection. In this dissertation, special characteristics of the connected closed-loop inverter and rectifier have been thoroughly analyzed, with particular interest in their impact on fault behaviors of the induction motor and the claw-pole generator. Based on the findings obtained from the theoretical and experimental analysis, several sensorless thermal, mechanical, and insulation monitoring methods are proposed by smartly utilizing special features and capabilities of the connected power electronic converter. A simple and sensitive stator turn-fault detector is proposed for induction motors fed by closed-loop inverter. In addition, a stator thermal monitoring method based on active DC current injection and direct voltage estimation is also proposed to prevent the closed-loop controlled induction motors from thermally overloading. The performance of both methods is demonstrated by extensive experimental results. Methods to detect serpentine belt slip, serpentine belt defect, rotor eccentricity have been proposed for claw-pole generators using only the available electric sensor information. Methods to detect and protect stator turn faults in claw-pole generators are also presented in this dissertation. Lastly, a novel method to detect the generalized bearing roughness fault is proposed. All the proposed condition monitoring techniques have been validated by experimental results.

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Gao, Yuan, and 高源. "Control of chaos in advanced motor drives." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45014784.

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Grubic, Stefan. "Online monitoring of turn insulation deterioration in mains-fed induction machines using online surge testing." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41131.

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The development of an online method for the early detection of a stator turn insulation deterioration is the objective of the research at hand. A high percentage of motor breakdowns is related to the failure of the stator insulation system. Since most of the stator insulation failures originate in the breakdown of the turn-to-turn insulation, the research in this realm is of great significance. Despite the progress that has been made in the field of stator turn fault detection methods, the most popular and the best known ones are still limited to the detection of solid turn faults. The time span between a solid turn fault and the breakdown of the primary insulation system can be as short as a few seconds. Therefore, it is desirable to develop a method capable of detecting the deterioration of the turn insulation as early as possible and prior to the development of a solid turn fault. The different stresses that cause the aging of the insulation and eventually lead to failure are described as well as the various patterns of an insulation failure. A comprehensive literature survey shows the methods presently used for the monitoring of the turn insulation. Up to now no well-tested and reliable online method that can find the deterioration of the turn insulation is available. The most commonly used turn insulation test is the surge test, which, however, is performed only when the motor is out of service and disconnected from the supply. So far no research at all has been conducted on the application of an online surge test. The research at hand examines the applicability of the surge test to an operating machine. Various topologies of online surge testing are examined with regard to their practicability and their limitations. The most practical configuration is chosen for further analysis, implementation and development. Moreover, practical challenges are presented by the non-idealities of the induction machine like the eccentricity of the rotor and the rotor slotting, and have to be taken into account. Two solutions to eliminate the influence of the rotor position on the surge waveform are presented. Even though the basic concepts of online surge testing can be validated experimentally by a machine with a solid turn fault, it is preferable to use a machine with a deteriorated turn insulation. Therefore, a method, which does not require complex and expensive hardware, to experimentally emulate the turn insulation breakdown is implemented. The concepts at any stage of the work are supported by simulations and experimental results. In addition, the theory of surge testing is further developed by giving new definitions of the test's sensitivity, i.e., the frequency sensitivity and the error area ratio (EAR) sensitivity.

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Tallam, Rangarajan M. "Current-based sensorless detection of stator winding turn faults in induction machines." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/13429.

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Dissertations / Theses on the topic 'Electric machinery'

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