Journal articles: 'High frequency transformers'

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Teruo Mendes de Souza, Diego, Bruno Valverde, and José Antenor Pomilio. "OVERVOLTAGE PROTECTION FOR HIGH FREQUENCY HIGH VOLTAGE POWER TRANSFORMERS." Eletrônica de Potência 25, no. 1 (February 5, 2020): 125–34. http://dx.doi.org/10.18618/rep.2020.1.0045.

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Seheda, M. S., P. F. Gogolyuk, and Y. V. Blyznak. "High-frequency periodic processes in two-winding power transformers." Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu, no. 6 (2021): 96–100. http://dx.doi.org/10.33271/nvngu/2021-6/096.

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Purpose. Mathematical modeling of high-frequency periodic processes in winding power transformers to improve the technology of their design and operation. Methodology. The methods of the formation of mathematical models for the research of high-frequency periodic processes in transformers and methods of solving systems of partial differential equations are applied. Findings. The mathematical model for the research of high-frequency periodic processes in two-winding transformers, with adequate considering of electromagnetic connections of windings and structural parameters of transformers, is created. Originality. To form a mathematical model for the research of high-frequency periodic processes, a substitute scheme of a two-windings transformer, taking into account the parameters of the electric and magnetic circuits of windings and electromagnetic connections between them, is proposed. Practical value. The mathematical model, which allows analyzing the voltage distribution in the transformer windings for high-frequency periodic processes in windings, and adjusting their insulating abilities, is created.

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ÖZÜPAK, Yıldırım. "Medium Frequency Electric Field Analysis of Power Transformers in High Voltage System." BEN Vol:2 Issue:3 2021 2, no. 3 (February 8, 2021): 1–5. http://dx.doi.org/10.36937/ben.2021.003.001.

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Electronic power transformers (EPT) are transformers that are smaller in size and volume compared to conventional 50 Hz frequency transformers. Medium frequency transformers (MFT) have begun to become important components in high voltage and high power energy conversion systems such as EPTs. In this study, the electric field distribution of these transformers is discussed. The electric field distributions in the transformer have been obtained using the two-dimensional finite element method (FEM). Besides, maximum electric field intensities were obtained in the study. ANSYS@Maxwell simulation program, which realizes a solution based on FEM, was used for these analyzes. Electromagnetic field analyzes of the same transformer under normal conditions were also performed to compare the analyzes. Besides, the values obtained from the high-frequency analysis, the values obtained from the study below 50 Hz frequency, and the values obtained experimentally were compared. In this way, the stress in the insulation material of the transformer and the weak parts of the insulation material were detected. It is expected that the method used will contribute to future studies to examine the results of the electric field distribution analysis of transformers.

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Yoon, Yeunggurl, Yongju Son, Jintae Cho, SuHyeong Jang, Young-Geun Kim, and Sungyun Choi. "High-Frequency Modeling of a Three-Winding Power Transformer Using Sweep Frequency Response Analysis." Energies 14, no. 13 (July 3, 2021): 4009. http://dx.doi.org/10.3390/en14134009.

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A power transformer is an essential device for stable and reliable power transfer to customers. Therefore, accurate modeling of transformers is required for simulation-based analysis with the model. The paper proposes an efficient and straightforward parameter estimation of power transformers based on sweep frequency response analysis (SFRA) test data. The method first develops a transformer model consisting of repetitive RLC sections and mutual inductances and then aligns the simulated SFRA curve with the measured one by adjusting parameters. Note that this adjustment is based on individual parameter impacts on the SFRA curve. After aligning the two curves, the final transformer model can be obtained. In this paper, actual single-phase, three-winding transformer model parameters were estimated based on field SFRA data, showing that SFRA curves simulated from the estimated model are consistent with the measured data.

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Shen, Zhan, Bingxin Xu, Chenglei Liu, Cungang Hu, Bi Liu, Zhike Xu, Long Jin, and Wu Chen. "The Modeling and Simplification of a Thermal Model of a Planar Transformer Based on Internal Power Loss." Sustainability 14, no. 19 (September 21, 2022): 11915. http://dx.doi.org/10.3390/su141911915.

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With the development of high-performance wide-band-gap devices and increasing converter frequency, planar transformers are widely used in high-frequency and high-power-density power conversions. Due to the skin effect and proximity effect, accurate thermal analysis and a simplified thermal model of planar transformers are needed for quick thermal verification as well as system design. This paper proposes two thermal simplification models based on the planar transformer’s thermal impedance network. The internal power loss and thermal coupling between each component are first analyzed. Then, based on thermal radiation theory, the simplified thermal model of the planar transformer is presented. It only requires the input of the total power loss of the planar transformer to calculate the temperature rise, and it does not need the power loss of each component. Finally, the simulation and experimental verification are carried out on a MHz prototype.

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Tian, Zheng Qi, Zhen Hua Li, and Yue Tong. "An Innovative Electronic Current Transformer Applied in High Voltage Systems." Advanced Materials Research 301-303 (July 2011): 1471–76. http://dx.doi.org/10.4028/www.scientific.net/amr.301-303.1471.

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With the development of power system, Conventional current transformers (CTs) show a growing number of shortcomings. For better performances, Electronic Current Transformers (ECTs) are researched to replace CT. But high price, unsatisfactory life and unpredictable reliability hold back their industrializations. Employing the insulation structure of traditional inverted SF6transformers and the new sensing principle at the same time, using high-precision digital integration algorithm which has higher precision to extracting the power frequency signal, an innovative electronic current transformer is introduced in this paper. Test results show that the transformer has high accuracy, low price, good stability, wide frequency response and long life.

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Gutten, Miroslav, Daniel Korenciak, Matej Kucera, Richard Janura, Adam Glowacz, and Eliasz Kantoch. "Frequency and time fault diagnosis methods of power transformers." Measurement Science Review 18, no. 4 (August 1, 2018): 162–67. http://dx.doi.org/10.1515/msr-2018-0023.

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Abstract The authors describe experimental and theoretical analyses of faults of power transformer winding. Faults were caused by mechanical effect of short-circuit currents. Measurements of transformer were carried out in high-voltage laboratory. Frequency and time diagnostic methods (method SFRA - Sweep Frequency Response Analysis, impact test) were used for the analyses. Coils of transformer windings were diagnosed by means of the SFRA method and the time impact test. The analyzed methods had a significant sensitivity to a relatively small deformation of coil. In the analysis a new technique for analyzing the effects of short-circuit currents is introduced. This technique is developed for high-voltage transformers (different types of power). The proposed analyses show that it is necessary to analyze the value of short-circuit current. Short-circuit current represents a danger for the operation of the power transformer. The proposed approach can be used for other types of transformers. Moreover, the presented techniques have a potential application for fault diagnosis of electrical equipment such as: transformers and electrical machines.

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Braña, L., A. Costa, and R. Lopes. "Development of a power transformer model for high-frequency transient phenomena." Renewable Energy and Power Quality Journal 19 (September 2021): 217–21. http://dx.doi.org/10.24084/repqj19.260.

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In recent years, the proliferation of distributed renewable energy sources and the application of new rules for the exploitation of electrical networks imposed by the markets have dictated increasingly demanding operating conditions for electric power transformers, creating new challenges in their exploration and conservation. Transformers that, in addition to the transmission lines, are certainly the most important and critical element of any electrical energy system. Adequate models are necessary to accurately describe transformer behavior and internal response when submitted to different external requests imposed by the network, particularly during transient phenomena, as well as, to properly assess system vulnerabilities and network optimization. This effort is being carried out today by several research groups in the world, namely from Cigré and IEEE. In this work, a transformer model to be integrated into a timedomain equivalent circuit is developed and discussed. Results obtained with this model are compared with measurements obtained by the Cigré JWG A2/C4.52 in a power transformer used as a reference for the working group.

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Morrill, M. A., V. A. Caliskan, and C. Q. Lee. "High-frequency planar power transformers." IEEE Transactions on Power Electronics 7, no. 3 (July 1992): 607–13. http://dx.doi.org/10.1109/63.145149.

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Jiang, Ting, Jian Feng Jiang, and Xi Jun Yang. "Research on Multi-Stage Series-Connection High-Voltage High-Power Matrix Converter." Advanced Materials Research 347-353 (October 2011): 843–47. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.843.

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Charge storage is an important research topic in smart grid and distributed generation system, pumped storage as one of the most popular large-scale charge storage methods has attracted increasing attention. However, the motor generator of the pumped charge station has high input voltage and heavy load, so in order to get grid connected safely, being soft started by a high voltage converter is necessary. In the view of the existing high voltage high power converters, only the voltage source inverter Multi-stage Series-connection high voltage frequency converters are suitable for this application, and this paper gives analysis of such converters. Based on Carrier Wave Phase-Shifted modulation, this paper proposes a multi-stage Series-connection high voltage frequency converter with balanced output power of the step-down transformer’s secondary windings, in which a winding burdens three symmetry three-phase to single-phase MC outputs, and the same phase outputs of the MC are cascaded at the secondary side of the transformers, letting out one phase of high-voltage AC output. The circuit is consisted of a step-down industry frequency transformer at the network side, three-phase to single-phase MC arrays, a step-up high frequency transformer at the load side and filter components. The simulation result based on MATLAB/SIMULINK shows that the proposed multi-stage Series-connection high voltage frequency converter is feasible and low-cost.

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LARIN, Vasily S., and Daniil A. MATVEEV. "Approximation of Transient Resonance Voltages and Currents in Power Transformer Windings to Determine Their Natural Frequencies and Damping Factors." Elektrichestvo 12, no. 12 (2020): 44–54. http://dx.doi.org/10.24160/0013-5380-2020-12-44-54.

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Transient interaction between power transformers and power cable lines may give rise to resonance overvoltages in the transformer primary windings. To develop protection measures against resonance overvoltages and to design transformers resistant to resonance overvoltages, it is necessary to know the natural frequencies of the transformer windings. Recent years have seen very rapid development of transformer windings high-frequency models. However, the mathematical models used in practice, which came from calculations of impulse overvoltages in transformer windings, reproduce the frequency dependences of losses and damping at natural frequencies with insufficient accuracy. To verify and improve the mathematical models used for analyzing high-frequency processes in transformer windings, it is necessary to have sufficient experimental data on the values of natural frequencies and damping factors. Methods for experimentally determining the natural frequencies and damping factors of power transformer windings are considered. Theoretical principles and analytical expressions for transient voltages and currents obtained for simplified equivalent circuits of windings with lumped parameters are given. An approach is proposed, according to which the transient voltages and currents in the winding are represented as the sum of steady-state and free components. The free component is then approximated using the theoretical expressions obtained for the equivalent circuits of the windings. The results of applying the approach to approximating the transient voltage at the midpoint and the current in the neutral of a dry-type transformer’s high-voltage winding are presented.

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Rigot, Valentin, Tanguy Phulpin, Jihen Sakly, and Daniel Sadarnac. "A New 7 kW Air-Core Transformer at 1.5 MHz for Embedded Isolated DC/DC Application." Energies 15, no. 14 (July 19, 2022): 5211. http://dx.doi.org/10.3390/en15145211.

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This paper presents the study of air-core transformers for electric vehicles, developing them for medium-power (tens of kWs) converter applications specifically used at a high frequency. Air-core transformers have the advantage of lacking magnetic saturation and iron losses, making them suitable for high-frequency applications. We designed and manufactured a transformer for a determined frequency and inductance value. The design of this passive component aims to both keep the magnetic field inside the transformer and manage the thermal energy efficiently. The electrical, magnetic, and thermal properties are simulated and then verified by experiments with a specific test bench. The transformer reaches high performances for a higher frequency than usual for an equivalent power transfer in automotive applications.

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Chojowski, Maciej, Marcin Baszyński, Robert Sosnowski, and Aleksander Dziadecki. "High-Frequency Current Transformers Cascade for Power Electronics Measurements." Sensors 22, no. 15 (August 4, 2022): 5846. http://dx.doi.org/10.3390/s22155846.

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High-frequency current transformers (HFCT) are widely used to measure fast transient current. Their advantages are simple structure and relatively moderate price. Their lower and upper bandwidth are limited, but the HFCT can be easily applied to many measuring applications in power electronics. The disadvantages of HFCT are substantial dimensions and a large weight. The paper proposes a system of a cascade connection of two transformers, which allows us to reduce these disadvantages. The properties of such an HFCT combination were investigated and described. In the article, the expression for double current transformer transmittances is derived. The frequency response of the sensor was determined, and the results were verified in a practical arrangement. An experimental setup of a cascade CT connection was made and tested, allowing for fast-changing signals in transients to be measured. This paper presents the theoretical basis and results of laboratory work on a wide range of static and dynamic tests of the proposed sensor.

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Jiang, Jun, Mingxin Zhao, Chaohai Zhang, Min Chen, Haojun Liu, and Ricardo Albarracín. "Partial Discharge Analysis in High-Frequency Transformer Based on High-Frequency Current Transducer." Energies 11, no. 8 (August 1, 2018): 1997. http://dx.doi.org/10.3390/en11081997.

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High-frequency transformers are the core components of power electronic transformers (PET), whose insulation is deeply threatened by high voltage (HV) and high frequency (HF). The partial discharge (PD) test is an effective method to assess an electrical insulation system. A PD measurement platform applying different frequencies was set up in this manuscript. PD signals were acquired with a high-frequency current transducer (HFCT). For improving the signal-to-noise (SNR) ratio of PD pulses, empirical mode decomposition (EMD) was used to increase the SNR by 4 dB. PD characteristic parameters such as partial discharge inception voltage (PDIV) and PD phase, number, and magnitude were all analyzed as frequency dependent. High frequency led to high PDIV and a smaller discharge phase region. PD number and magnitude were first up and then down as the frequency increased. As a result, a suitable frequency for evaluating the insulation of high-frequency transformers is proposed at 8 kHz according to this work.

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Ataullah, Haris, Taosif Iqbal, Ihsan Ullah Khalil, Al-Sharef Mohammad, Nasim Ullah, and Mohamed Emad Farrag. "Analysis and Verification of Leakage Inductance Calculation in DAB Converters Based on High-Frequency Toroidal Transformers under Different Design Scenarios." Energies 15, no. 17 (August 25, 2022): 6176. http://dx.doi.org/10.3390/en15176176.

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High-frequency transformers are becoming an essential component in the integration of power resources that rely on power electronic converters; their efficiency and performance are influenced by parasitic characteristics in the interface. In this article, the design of a high-frequency toroidal transformer has been explained in detail using the ANSYS Maxwell platform. Various parameters, such as leakage inductance, magnetic flux density, magnetic field strength and uniform magnetic flux line are analyzed using Finite element analysis. High-frequency transformers using a toroidal core with different winding configurations are examined and all parameters obtained through simulation are validated by an analytical approach. Analysis of each design is based on its leakage inductances, which will aid in the appropriate selection of transformers as a function of their operating frequency. This analysis is expected to guide designers to optimize the high-frequency transformer parameters based on practical applications. The optimized parameters are then applied for a dual active bridge (DAB) converter within MATLAB/Simulink to verify the design process. A prototype has been built to validate the simulation and design procedure. The results obtained from both simulation and experiments are compared and show great correlation.

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Dong, Yue, Xiao Xin Chen, Yan Ran Li, Yi Ming Zhang, and Chong Wei. "Frequency Characteristics Analysis of High Frequency Current Transformers." Advanced Materials Research 945-949 (June 2014): 1996–2004. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.1996.

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In this paper, the equivalent model of high frequency current transformers (HFCT) for partial discharge online monitoring and its major parameters’ influence on amplitude-and phase frequency characteristics are derived. An optimized design for HFCT for partial discharge online monitoring is summarized.

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Li, Yinan, Rui Wang, Liping Zhong, Limin Mao, Chuan Sun, Xiaodong Li, and Song Hu. "Analysis and Design of a High-Frequency Isolated Dual-Transformer DC-DC Resonant Converter." Electronics 12, no. 1 (December 27, 2022): 103. http://dx.doi.org/10.3390/electronics12010103.

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This paper presents the operation, analysis, design, simulation, and experimental results for a proposed Dual-Transformer DC-DC Resonant Converter (DTRC). A three-arm bridge is employed on the input side and an H-type bridge is employed on the output side of the DTRC, and the two bridges are connected with two high-frequency (HF) transformers. By optimizing the ratio k of the two HF transformers, the proposed DTRC has a lower boundary power for losing zero-voltage switching (ZVS). That means the DTRC has a wider ZVS operation range and lower switching loss when compared with a traditional soft-switching pulse width modulation (PWM) resonant converter. The operation principle, power transfer, ZVS characteristics, and design procedures are analyzed in detail. Both simulation and experimental results prove the feasibility and superiority of the proposed Dual-Transformer DC-DC Resonant Converter.

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Himanshu, Harsimran Singh, Pandiyan Kumar, Muhammad Ali, Ho Lee, Muhammad Khan, Gwan Park, and Hee-Je Kim. "High Frequency Transformer’s Parasitic Capacitance Minimization for Photovoltaic (PV) High-Frequency Link-Based Medium Voltage (MV) Inverter." Electronics 7, no. 8 (August 8, 2018): 142. http://dx.doi.org/10.3390/electronics7080142.

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The high-frequency-based medium voltage (MV) inverter is used in renewable energy power sources for power transmission. However, power quality is compromised as a result of the increase in common mode noise currents by the high inter-winding parasitic capacitance in high-frequency link transformers. This fast voltage transient response leads to harmonic distortion and transformer overheating, which causes power supply failure or many other electrical hazards. This paper presents a comparative study between conventional and modified toroid transformer designs for isolated power supply. A half bridge high-frequency (10 kHz) MV DC–AC inverter was designed along with power source; a 680 W solar module renewable system was built. An FEM-simulation with Matlab-FFT analysis was used to determine the core flux distribution and to calculate the total harmonics distortion (THD). A GWInstek LCR meter and Fluke VT04A measured the inter-winding capacitance and temperature in all four transformer prototypes, respectively. The modified design of a toroid ferrite core transformer offers more resistance to temperature increase without the use of any cooling agent or external circuitry, while reducing the parasitic capacitance by 87%. Experiments were conducted along with a mathematical derivation of the inter-winding capacitance to confirm the validity of the approach.

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Falah Hassan, Reem, and Kassim Rasheed Hameed. "Design of high frequency transformers in different shape of core using matlab program." Indonesian Journal of Electrical Engineering and Computer Science 20, no. 3 (December 1, 2020): 1159. http://dx.doi.org/10.11591/ijeecs.v20.i3.pp1159-1172.

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This paper deals with the design, simulation and implementation of the high-frequency transformer for a push-pull converter. It also includes transformer design and simulation for two switches, two outputs forward converter. Design these transformers by building a program, this program is designed in MATLAB software using a graphical user interface (GUI). The program is aimed to reduce the efforts and reduce the time compare with the manual design which takes time and effort. This paper provided the shape and geometry of the core that can influence the efficiency of the converter by designing these transformers in two types of core. The design results were validated by simulation in power simulation software (PSIM), and compare the results of simulation and design.

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Ningning Wang, H. Hauser, T. O'Donnell, M. Brunet, P. McCloskey, and S. C. O'Mathuna. "Modeling of high-frequency micro-transformers." IEEE Transactions on Magnetics 40, no. 4 (July 2004): 2014–16. http://dx.doi.org/10.1109/tmag.2004.832174.

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Farahani, Hassan Feshki, and Mohammad Khalili. "Investigation the Effect of Core Type on the Leakage Inductance in the High Frequency Transformers." Advanced Materials Research 433-440 (January 2012): 3890–94. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.3890.

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One of the most important problems in high-frequency transformers is leakage flux which is inevitable and can lead to increase the leakage inductance. The leakage inductance has different effects on pulse transformers `operation which among them the effect on rise time can be mentioned that can change the output waveform. Although inductance value can not be zero, it can be reduced to some extent. One of the ways is to choose the core type. According to core type, windings in transformer can be winded in a way that results in leakage inductance reduction. In this paper, two kinds of transformers with two different cores are modeled and simulated in ANSYS which are equal in transforming power and different in windings area. Also in this paper, the effect of core type on leakage inductance value is studied by using the obtained results.

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Banchuin, Rawid, and Roungsan Chaisricharoen. "Vector SDE Based Stochastic Analysis of Transformer." ECTI Transactions on Computer and Information Technology (ECTI-CIT) 15, no. 1 (January 5, 2021): 82–107. http://dx.doi.org/10.37936/ecti-cit.2021151.188931.

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In this research, the stochastic behaviours oftransformer have been analysed by using the stochasticdifferential equation approach where both noise in thevoltage source applied to the transformer and the randomvariations in elements and parameters of transformers havebeen considered. The resulting vector stochasticdifferential equations of the transformer have been bothanalytically and numerically solved in the Ito sense wherethe Euler-Maruyama scheme has been adopted fordetermining the numerical solutions which have been theirsample means have been used for verification. With theobtained analytical and numerical solutions, the stochasticproperties of the transformer’s electrical quantities havebeen studied and the influences of noise in the voltagesource and random variations in elements and parametersof transformers to those electrical quantities have beenanalysed. The causes of high and low frequency stochasticvariations of such electrical quantities in both transient andsteady state have been pointed out. Moreover, furtherextension of our stochastic differential equations and therelated mathematical formulations has also been given.

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Umemoto, Takahiro, and Stefan Tenbohlen. "Novel Simulation Technique of Electromagnetic Wave Propagation in the Ultra High Frequency Range within Power Transformers." Sensors 18, no. 12 (December 3, 2018): 4236. http://dx.doi.org/10.3390/s18124236.

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Diagnoses of power transformers by partial discharge (PD) measurement are effective to prevent dielectric failures of the apparatus. Ultra-high frequency (UHF) method has recently received attention due to its various advantages, such as the robustness against external noise and the capability of PD localization. However, electromagnetic (EM) waves radiated from PD tend to suffer attenuation before arriving at UHF sensors, because active part of the transformer disturbs the EM wave propagation. In some cases, that results in poor detection sensitivity. To understand propagation and attenuation characteristics of EM waves and to evaluate the detection sensitivity quantitatively, a computational approach to simulate the EM wave propagation is important. Although many previous researches have dealt with EM wave simulation for transformers, validations of those simulations by comparing with the experimental ones have seldom been reported. In this paper, cumulative energies, signal amplitudes and propagation times of EM waves were measured using a 630 kVA transformer. EM wave propagation was computed using the time-domain finite integration technique and the results were compared with the experimentally obtained ones. These simulation results showed good agreement with the experimental ones. The results can serve as guidelines to improve the efficiency of UHF PD detection and offer the possibility to achieve optimal placement of UHF sensors in power transformers.

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Zhang, Ming, Kaicheng Li, Shunfan He, and Jun Wang. "DESIGN AND TEST OF A NEW HIGH-CURRENT ELECTRONIC CURRENT TRANSFORMER WITH A ROGOWSKI COIL." Metrology and Measurement Systems 21, no. 1 (March 1, 2014): 121–32. http://dx.doi.org/10.2478/mms-2014-0012.

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Abstract This paper describes the design and test of a new high-current electronic current transformer based on a Rogowski coil. For better performances, electronic current transformers are used to replace conventional electro-magnetic inductive current transformers based on ferromagnetic cores and windings to measure high-current on the high voltage distribution grids. The design of a new high-current electronic current transformer is described in this paper. The principal schemes of the prototype and partial evaluation results are presented. Through relative tests it is known that the prototype has a wide dynamic range and frequency band, and it can allow high accuracy measurements.

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Soomro, Amir M., Shahnawaz F. Khahro, and Xiao Zhong Liao. "Simulation for the Control Strategy of Three-Phase Boost-Half-Bridge (BHB) DC-DC Converter with Series Voltage Doubler Rectifiers through Three-Phase High Frequency Transformer." Applied Mechanics and Materials 325-326 (June 2013): 533–37. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.533.

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This paper presents simulation for the control strategy of three-phase boost-half-bridge (BHB) DC-DC converter with series voltage doubler rectifiers through three-phase high frequency transformer. The control strategy is consisting of three voltage loops. All the three voltage loops are independent of the input side and controls the input and output power balance from the secondary side of the high frequency transformers only. Moreover, the control strategy has been verified for its appropriate operation by simulating the above said configuration for the same turn ratios as well as for the mismatch turn ratios of high frequency transformers. Finally, the satisfactory simulation results for the proposed control strategy are presented.

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Besharatifard, Hamidreza, Saeed Hasanzadeh, Ehsan Heydarian-Forushani, Hassan Haes Alhelou, and Pierluigi Siano. "Detection and Analysis of Partial Discharges in Oil-Immersed Power Transformers Using Low-Cost Acoustic Sensors." Applied Sciences 12, no. 6 (March 16, 2022): 3010. http://dx.doi.org/10.3390/app12063010.

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Partial Discharge (PD) is one of the symptoms of an electrical insulation problem, and its permanence can lead to the complete deterioration of the electrical insulation in high-voltage equipment such as power transformers. The acoustic emission (AE) method is a well-known technique used to detect and localize PD activity inside oil-filled transformers. However, the commercially available monitoring systems based on acoustic sensors still have a high cost. This paper analyses the ability of low-cost piezoelectric sensors to identify PDs within oil-filled power transformers. To this end, two types of low-cost piezoelectric sensors were fully investigated using time-domain, frequency-domain, and time-frequency analysis, separately. Thereafter, the effectiveness of these sensors for PD detection and monitoring was studied. A three-phase distribution transformer filled with oil was examined. PDs were produced inside an oil-immersed transformer by applying a high voltage over two copper electrodes, and the AE sensors were coupled to the housing of the transformer. By extracting typical features from the AE signals, the PD signals were differentiated from on-site noise and interference. The AE signals were analyzed using acoustic signal metrics such as peak value, energy criterion, and other statistical parameters. The obtained results indicated that the used low-cost piezoelectric sensors have the capability of PD monitoring within power transformers.

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Berg, Heinz-Peter, and Nicole Fritze. "Risk and Consequences of Transformer Explosions and Fires in Nuclear Power Plants / Ryzyko I Konsekwencje Wybuchów Transformatora I Pożarów W Elektrowniach Jądrowych." Journal of KONBiN 23, no. 1 (September 1, 2012): 5–16. http://dx.doi.org/10.2478/jok-2013-0034.

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Abstract The high failure frequency and the resultant reliability and safety implications in recent years of transformers, in particular at nuclear power plants (NPP), required an in-depth assessment. Fires of main transformers are considered as critical because of the large quantity of oil in contact with high voltage elements. Therefore, these phenomena have been investigated in more detail using the information from the OECD FIRE database for NPP. 12.8 % of all fires and, thus, the most frequent fire source in this database are transformer fires, mainly fires of high voltage oil-filled transformers. Thus, possible diagnostic measures to avoid such events and enhance the reliability currently discussed in Germany are shortly described. Moreover, consequences of transformer failures with respect to a reliable electric power supply are addressed.

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Waltrich, Gierri. "Inductances Design of High-Frequency Coaxial Transformers." OALib 03, no. 07 (2016): 1–6. http://dx.doi.org/10.4236/oalib.1102820.

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Choi, Geun-Soo, Shin-Yong Yoon, Soo-Hyun Baek, and Yong Kim. "Power Loss Calculation of High Frequency Transformers." Journal of Electrical Engineering and Technology 1, no. 3 (September 1, 2006): 338–42. http://dx.doi.org/10.5370/jeet.2006.1.3.338.

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Rauls, Mark S., Donald W. Novotny, Deepakraj M. Divan, Robert R. Bacon, and Randal W. Gascoigne. "Multiturn High-Frequency Coaxial Winding Power Transformers." IEEE Transactions on Industry Applications 31, no. 1 (January 1995): 112–18. http://dx.doi.org/10.1109/28.363042.

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Wang, N., T. O’Donnell, H. Hauser, P. McCloskey, and S. C. O’Mathuna. "Hysteresis modelling of high-frequency micro-transformers." Journal of Magnetism and Magnetic Materials 272-276 (May 2004): E1763—E1764. http://dx.doi.org/10.1016/j.jmmm.2004.01.013.

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Abdi, B., A. A. Nasiri, M. H. Aslinezhad, and M. Abroshan. "Winding Considerations on the High Frequency Transformers." Energy Procedia 12 (2011): 656–61. http://dx.doi.org/10.1016/j.egypro.2011.10.089.

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Ricci, Stefano, and Dario Russo. "Linear Ultrasound Transmitter Based on Transformer with Improved Saturation Performance." Electronics 10, no. 2 (January 7, 2021): 107. http://dx.doi.org/10.3390/electronics10020107.

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Ultrasound methods are currently employed in a wide range of applications. They are integrated in complex electronics systems, like clinical echographs, but also in small and compact boards, like industrial sensors, embedded systems, and portable devices. Ultrasound waves are typically generated by energizing a piezoelectric transducer through a high-voltage sequence of small sinusoidal bursts. Moreover, in several applications, the ultrasound board should work in a wide frequency range. This makes the transmitter, i.e., the electronics that drives the transducer, a key part of the circuit. The use of a small transformer simplifies the electronics and reduces the need of high-voltage power sources. Unfortunately, the transformer magnetic core, when subjected to the sequence of bursts employed in ultrasound, is particularly prone to saturation. This phenomenon limits the maximum voltage and/or the minimum frequency the transformer can be employed for. In this work, a transmitter based on a transformer is proposed. Inspired by the technique currently employed in the power network transformers, we added a prefluxing circuit, which improves the saturation performance 2-fold. The proposed transmitter was implemented in a test board and experimented with two commercial transformers at 80 Vpp. Measurements show that the proposed prefluxing circuit moves down the minimum usable frequency 2-fold: from 400 to 200 kHz for one of the two transformers, and from 2.4 to 1.2 MHz for the other.

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Ricci, Stefano, and Dario Russo. "Linear Ultrasound Transmitter Based on Transformer with Improved Saturation Performance." Electronics 10, no. 2 (January 7, 2021): 107. http://dx.doi.org/10.3390/electronics10020107.

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Ultrasound methods are currently employed in a wide range of applications. They are integrated in complex electronics systems, like clinical echographs, but also in small and compact boards, like industrial sensors, embedded systems, and portable devices. Ultrasound waves are typically generated by energizing a piezoelectric transducer through a high-voltage sequence of small sinusoidal bursts. Moreover, in several applications, the ultrasound board should work in a wide frequency range. This makes the transmitter, i.e., the electronics that drives the transducer, a key part of the circuit. The use of a small transformer simplifies the electronics and reduces the need of high-voltage power sources. Unfortunately, the transformer magnetic core, when subjected to the sequence of bursts employed in ultrasound, is particularly prone to saturation. This phenomenon limits the maximum voltage and/or the minimum frequency the transformer can be employed for. In this work, a transmitter based on a transformer is proposed. Inspired by the technique currently employed in the power network transformers, we added a prefluxing circuit, which improves the saturation performance 2-fold. The proposed transmitter was implemented in a test board and experimented with two commercial transformers at 80 Vpp. Measurements show that the proposed prefluxing circuit moves down the minimum usable frequency 2-fold: from 400 to 200 kHz for one of the two transformers, and from 2.4 to 1.2 MHz for the other.

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Beura, Chandra Prakash, Michael Beltle, Philipp Wenger, and Stefan Tenbohlen. "Experimental Analysis of Ultra-High-Frequency Signal Propagation Paths in Power Transformers." Energies 15, no. 8 (April 9, 2022): 2766. http://dx.doi.org/10.3390/en15082766.

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Ultra-high-frequency (UHF) partial discharge (PD) monitoring is gaining popularity because of its advantages over electrical methods for onsite/online applications. One such advantage is the possibility of three-dimensional PD source localization. However, it is necessary to understand the signal propagation and attenuation characteristics in transformers to improve localization. Since transformers are available in a wide range of ratings and geometric sizes, it is necessary to ascertain the similarities and differences in UHF signal characteristics across the different designs. Therefore, in this contribution, the signal attenuation and propagation characteristics of two 300 MVA transformers are analyzed and compared based on experiments. The two transformers have the same rating but different internal structures. It should be noted that the oil is drained out of the transformers for these tests. Additionally, a simulation model of one of the transformers is built and validated based on the experimental results. Subsequently, a simulation model is used to analyze the electromagnetic wave propagation inside the tank. Analysis of the experimental data shows that the distance-dependent signal attenuation characteristics are similar in the case of both transformers and can be well represented by hyperbolic equations, thus indicating that transformers with the same rating have similar attenuation characteristics even if they have different internal structures.

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Zhang, Xian Jin, and Bu Gen Wang. "Applications of DC Transformer in DC Distributed Generations System." Advanced Materials Research 706-708 (June 2013): 1755–58. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.1755.

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DC transformer with high frequency and efficiency under a fixed duty cycle is widely used in dc distributed generations. In this paper, the topologies and equivalent circuits of single /bidirectional full-bridge non-resonant DC transformers are presented. And the configurations of the input-series output-parallel and input-parallel output-series DC transformers are also proposed for reducing voltage stress of power devices. The example consisting of DC transformers in a distributed generation system based on DC grid is shown. Finally, simulation results verify the feasibility.

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Wang, Hao, and Dian Ren Chen. "Chip Technology Based on High Efficiency DC Power Supply." Advanced Materials Research 1030-1032 (September 2014): 1384–87. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.1384.

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The switching power supply is the use of modern power electronics, by controlling the switching transistor turn-on and turn-off time ratio, maintaining a stable output voltage of the power supply. Switching power supply technology at the core, it is mainly divided into AC / DC and DC / DC two categories. Switching power supply eliminates bulky frequency transformers, replacing tens of kHz, MHz or even hundreds of kHz frequency transformer. Since the adjustment pipe work in the off state, and thus low power consumption and high efficiency.

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Khan, Saniya, Khaliqur Rahman, Mohd Tariq, Salman Hameed, Basem Alamri, and Thanikanti Sudhakar Babu. "Solid-State Transformers: Fundamentals, Topologies, Applications, and Future Challenges." Sustainability 14, no. 1 (December 29, 2021): 319. http://dx.doi.org/10.3390/su14010319.

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Solid-state transformers (SSTs) have emerged as a superior alternative to conventional transformers and are regarded as the building block of the future smart grid. They incorporate power electronics circuitry and high-frequency operation, which allows high controllability and enables bi-directional power flow, overcoming the limitations of conventional transformers. This paper presents a detailed analysis of the solid-state transformer, expounding the fundamentals, converter topologies, applications, and future challenges of the SST in a systematic manner. The paper discusses the necessity of improved replacement of the low-frequency transformers (LFTs) and presents the configuration of SST. It presents SST fundamentals in individual stages and explores its origin and evolution. The basic topologies, their specifications, and control strategies are also described. The applications of SST as a replacement of LFTs are discussed along with recent applications. The future challenges for real-time implementation of SSTs are explored, and research directions are proposed.

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Gonzalez-Garcia, Carlos, and Jorge Pleite. "Transformer Model in Wide Frequency Bandwidth for Power Electronics Systems." Advances in Power Electronics 2013 (January 28, 2013): 1–8. http://dx.doi.org/10.1155/2013/249146.

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The development of the smart grids leads to new challenges on the power electronics equipment and power transformers. The use of power electronic transformer presents several advantages, but new problems related with the application of high frequency voltage and current components come across. Thus, an accurate knowledge of the transformer behavior in a wide frequency range is mandatory. A novel modeling procedure to relate the transformer physical behavior and its frequency response by means of electrical parameters is presented. Its usability is demonstrated by an example where a power transformer is used as filter and voltage reducer in an AC-DC-AC converter.

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Kao, Hsuan-Ling. "On-Chip Voltage-Controlled Oscillator Based on a Center-Tapped Switched Inductor Using GaN-on-SiC HEMT Technology." Electronics 10, no. 23 (November 25, 2021): 2928. http://dx.doi.org/10.3390/electronics10232928.

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This study presents a voltage-controlled oscillator (VCO) in a cross-coupled pair configuration using a multi-tapped switched inductor with two switch-loaded transformers in 0.5 µm GaN technology. Two switch-loaded transformers are placed at the inner and outer portions of the multi-tapped inductor. All the switches are turned off to obtain the lowest sub-band. The outer transformer with three pairs of switches is turned on alternately to provide three sub-band modes. A pair of switches at the inner transformer provide a high-frequency band. Two switch-loaded transformers are turned on to provide the highest sub-band. Six modes are selected to provide a wide tuning range. The frequency tuning range (FTR) of the VCO is 27.8% from 3.81 GHz to 8.04 GHz with a varactor voltage from 13 V to 22 V. At a 1 MHz frequency offset from the carrier frequency of 4.27 GHz, the peak phase noise is −119.17 dBc/Hz. At a power supply of 12 V, the output power of the carrier at 4.27 GHz is 20.9 dBm. The figure of merit is −186.93 dB because the VCO exhibits a high output power, low phase noise, and wide FTR. To the best of the author’s knowledge, the FTR in VCOs made of GaN-based high electron mobility transistors is the widest reported thus far.

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Pavlovsky, M., S. W. H. de Haan, and J. A. Ferreira. "High-Performance Thermal Management for High-Power High-Frequency Transformers." EPE Journal 19, no. 2 (June 2009): 20–27. http://dx.doi.org/10.1080/09398368.2009.11463713.

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LARIN, Vasily S., and Daniil A. MATVEEV. "Determination of the attenuation coefficients from the measured frequency characteristics of the windings of power transformers. Part 1. Theoretical consideration." Elektrichestvo 1, no. 1 (2021): 13–22. http://dx.doi.org/10.24160/0013-5380-2021-1-13-22.

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To model high-frequency processes and determine the stresses on the internal insulation of transformer windings, reliable high-frequency models of power transformers are required. The accuracy of modeling high-frequency resonance processes in the windings depends on how correctly the model reproduces the natural frequencies and damping of free oscillations in the windings. To construct and verify high-frequency models of power transformers, it is necessary to have experimentally obtained data on the values of damping factors. There is a known method for determining the winding damping factors based on measurements of the voltage transfer functions at the internal points of the windings and their subsequent processing using the vector fitting technique, but its application is not always possible in practice. The article presents the results of theoretical studies performed for a simplified transformer winding equivalent circuit. It is shown that the damping factors can be estimated from the width of the resonance peaks of the frequency responses of the voltage modulus and reactive component at the midpoint of the equivalent circuit, and from the input admittance resistive component and current in the neutral of the considered resonance circuit.

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Kheraluwala, M. H., D. W. Novotny, and D. M. Divan. "Coaxially wound transformers for high-power high-frequency applications." IEEE Transactions on Power Electronics 7, no. 1 (January 1992): 54–62. http://dx.doi.org/10.1109/63.124577.

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Cerpinska, Marina, Renars Vitols, and Oskars Simanis. "Electromagnetic Vibrations of Hydropower Generator Stator Core and Transformer Core at 100 Hz Frequency." Solid State Phenomena 260 (July 2017): 278–88. http://dx.doi.org/10.4028/www.scientific.net/ssp.260.278.

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This paper aimed to compare obtained results and collected theory for 100 Hz frequency vibration of hydropower generator stator core and transformer core. Electromagnetic vibration with 100 Hz frequency occurred both at slow-speed salient poles synchronous generator stator core and oil-filled power transformers tank, but the nature of hydropower and transformer 100 Hz vibration was different. The vibration analysis procedure and acceptable limits for hydropower generator stator core were already covered in the standards, while the health grade system for vibration measurements of power transformer has not beet yet developed. This study discussed the experimental results aiming to extend the knowledge about reasoning for non-existing statistical health grade system, based on power transformers vibrations, measured on tank. The experimental results of hydropower generator stator and power transformer spectrum were reported. Two salient pole hydropower generator stators and four transformers with different construction (including shell-type) and different cooling system (including air forced cooling system) were chosen to present vibration spectrum results. It was demonstrated that increasing clamping pressure of the core does not always reduce 100 Hz harmonic component neither for hydrogenerator stator, nor for transformer. Bad clamping pressure and defects in core, in contrary, will not result into increase of 100 Hz component for some units. Results showed that air forced cooling equipment (fans) would not add higher harmonics to vibration spectrum of the power transformer tank. It was shown that the shell-type construction of transformer core would not necessarily result in high vibration values on tank.

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Galipeau, James, and George Slama. "Characterization and Reliability Testing on an LTCC Transformer Operable to 250 °C." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, HITEC (January 1, 2012): 000354–60. http://dx.doi.org/10.4071/hitec-2012-tha24.

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Environments prone to vibration and shocks can cause premature failure in small wire-wound transformers due to cracked cores and broken wires. These problems are only exacerbated by temperatures exceeding 200 °C where the heat causes organic compounds to age rapidly. As more electronics are used in harsh, high temperature environments, high reliability, compact transformers for use in power, filtering, and isolation applications are needed. To address this need monolithic low-temperature co-fired ceramic transformers were developed. In this work transformers were made from a low-temperature, co-fire compatible, ferrite with a Curie temperature of 350 °C. The transformers were first subjected to a 2,000 hour life test at 250 °C in which the transformer was used to charge a load capacitor once every two seconds. The inductance, resistance, core loss, and saturation flux density of the transformers were measured at various temperatures. Additional testing focused on the effect of temperature on the device's frequency profile and performance changes under thermal cycling.

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Al-Ameri, Salem Mgammal, Abdulaziz Almutairi, Muhammad Saufi Kamarudin, Mohd Fairouz Mohd Yousof, Ahmed Abu-Siada, Mohamed Ibrahim Mosaad, and Saeed Alyami. "Application of Frequency Response Analysis Technique to Detect Transformer Tap Changer Faults." Applied Sciences 11, no. 7 (April 1, 2021): 3128. http://dx.doi.org/10.3390/app11073128.

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Power transformers are located in the electrical transmission and distribution networks where different voltage levels are needed. The turn ratio of the low voltage and high voltage windings is mechanically controlled by an on-load tap changer or de-energized tap changer. As the tap changer is the transformer’s only moving part, it is highly susceptible to mechanical failure and aging degradation. While some diagnostic tools have been used to determine the mechanical condition of tap changer contacts, not much attention was given to use the frequency response analysis to diagnose the transformer’s tap changers’ mechanical integrity. This paper is taking one step forward into maturing the application of the frequency response analysis (FRA) technique to detect transformer tap changer faults. In this regard, two common tap changer faults are created, and experimental testing for four FRA test configurations is conducted. For a better understanding of the tap changer fault mechanism, an electrical equivalent circuit model is proposed and designed using Simulink. The simulation and implementation of the equivalent circuits using MATLAB\R2018a.

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Pachowicz, Krzysztof. "High-Voltage Power Supply for High Repetitive Rate Marx Generator with Quasi-Resonant Zero-Current Switching Transistor Control Algorithm." Energies 15, no. 19 (September 21, 2022): 6902. http://dx.doi.org/10.3390/en15196902.

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Due to having a number of advantages, Marx generators are still the most widely used devices for generating high-voltage pulses in many fields of science and technology. To ensure their proper operation, especially when the generation of many frequent, highly repetitive pulses is required, a highly efficient high-voltage power supply is needed. The paper describes a specially developed power supply (input voltage 48 V DC, output voltage up to 50 kV) based on the conventional Full Bridge topology with two high-frequency high-voltage transformers and a 6-stage voltage multiplier. In order to avoid many problems caused by low coupling between primary and secondary windings of the transformers and the large parasitic capacitances of the secondary windings, a special quasi-resonant zero-current switching transistor control algorithm with variable switching frequency (dependent on output load) was developed. In the described method, the energy is supplied to the transformer in short pulses, when a pair of diagonal transistors of the full-bridge converter were turned on. Then, the freewheeling state is maintained until all of the energy stored in the leakage inductance of the transformer has been transferred to the secondary side, which means that the current in the primary windings drops to zero. This approach reduces energy losses, electromagnetic disturbances and prevents current distortion in primary winding.

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Farnesi, Stefano, Mario Marchesoni, Massimiliano Passalacqua, and Luis Vaccaro. "Solid-State Transformers in Locomotives Fed through AC Lines: A Review and Future Developments." Energies 12, no. 24 (December 10, 2019): 4711. http://dx.doi.org/10.3390/en12244711.

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One of the most important innovation expectation in railway electrical equipment is the replacement of the on-board transformer with a high power converter. Since the transformer operates at line-frequency (i.e., 50 Hz or 16 2/3 Hz), it represents a critical component from weight point of view and, moreover, it is characterized by quite poor efficiency. High power converters for this application are characterized by a medium frequency inductive coupling and are commonly referred as Power Electronic Transformers (PET), Medium Frequency Topologies or Solid-State Transformers (SST). Many studies were carried out and various prototypes were realized until now, however, the realization of such a system has some difficulties, mainly related to the high input voltage (i.e., 25 kV for 50 Hz lines and 15 kV for 16 2/3 Hz lines) and the limited performance of available power electronic switches. The aim of this study is to present a survey on the main solutions proposed in the technical literature and, analyzing pros and cons of these studies, to introduce new possible circuit topologies for this application.

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Jurišić, Bruno, Ivo Uglešić, Alain Xemard, and Françoise Paladian. "Case study on transformer models for calculation of high frequency transmitted overvoltages." Journal of Energy - Energija 63, no. 1-4 (July 4, 2022): 262–72. http://dx.doi.org/10.37798/2014631-4186.

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Events such as lightning, switching of vacuum circuit breaker or switching operations in gas insulated substation (GIS) generate high frequency overvoltages. An equipment in a transmission or a distribution system has to be protected against such phenomena. Unfortunately, the traditional transformer models available in Electromagnetic transient simulations program (EMTP-like) software packages are not capable of representing transformer behavior in a transient state, which includes high frequencies. Moreover, high frequency transformer models are often too complex or require confidential information on transformer geometry. However, in the design stage of insulation coordination it is particularly important to accurately calculate transmitted overvoltages through transformers. In the scope of this paper two different transformer models for high frequency, are developed in an EMTP-type software program. The first model named “Black box” derives solely from the values measured on the transformer terminals and does not require any knowledge of the transformer inner geometry. The second model named “Grey box”, is based on a lumped RLC parameters network, whose values are derived from the simple geometry of the transformer window and from the nameplate data. Furthermore, the models’ capabilities to characterize a transformer at high frequencies are analyzed. The case study is done on a distribution transformer which is to be located inside a power plant. The transmitted overvoltages calculated with the models in the EMTP-type software program are compared with measurements.

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Lin, Jing-Yuan, Hsuan-Yu Yueh, Yi-Feng Lin, and Pin-Hsien Liu. "Analysis and Design of Three-Phase LLC Resonant Converter with Matrix Transformers." Energies 15, no. 4 (February 11, 2022): 1315. http://dx.doi.org/10.3390/en15041315.

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This study presents the topology of a three-phase LLC resonant converter with matrix transformers. The three-phase LLC resonant converter has the advantages of conventional LLC resonant converters, including zero-voltage switching at the primary side, zero-current switching at the secondary side, high-frequency feasibility, and high efficiency. Moreover, it has additional advantages that differ from conventional LLC, including low output capacitor current ripple, natural current sharing in three resonant currents, and a high power level. As a result of the above mentioned characteristics, LLC topology has been used in many electric vehicle charging systems, server power systems, and other high-power applications. However, as the power level becomes higher and higher, the input voltage is usually too high to reduce conduction loss, and the output current also increases. This situation makes transformer design more difficult. The increasing current means more core and copper loss, and the heat dissipation of the transformer becomes more difficult. Matrix transformer technology can improve this problem directly and simply. By utilizing matrix transformers, which are primary series connected and secondary parallel connected, the primary voltage stress and secondary current stress of the transformers can be reduced, and the output current can be distributed. The analysis of the proposed converter in this study includes a circuit operation introduction, a time-domain analysis, calculation of the transfer ratio curve in the frequency domain, and a loss analysis. The theoretical analysis and performance of the proposed converter are verified. A three-phase LLC resonant converter with matrix transformers prototype is built with a high input voltage of 800-VDC and high output current of 200-A. The output voltage is 100-VDC. The waveform and efficiency data will be shown in the experimental results.

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Journal articles on the topic 'High frequency transformers'

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