研究者詳細 - 平木　英治

論文 - 平木　英治

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Impedance Matching to Maximize Induced Current in Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems

Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

2018 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 6194 - 6201 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Intermediate resonators (repeaters) of resonant inductive coupling wireless power transfer systems can improve the transmission distance as well as the output power. However, frequency bandwidths in which the repeater can operate effectively are very narrow because the repeater usually has a high quality-factor. Furthermore, these frequency bandwidths shift for the following two factors. The first factor is the intensity of the magnetic coupling between the repeater and the other resonator. The second factor is the variation in the natural resonance frequency of the resonators due to a production error, temperature characteristic, and aging degradation. Therefore, the repeater is not practical because the repeater requires accurate adjusting of the circuit parameters every time according to the various conditions. To address this problem, we propose an impedance matching method for the repeater. The proposed method can maximize the induced current in the repeater in wide frequency bandwidth regardless of the variations in the intensity of the magnetic coupling and the natural resonance frequency. Therefore, the proposed method can realize the repeater which can stably improve the performance of the wireless power transfer. Experiment and simulation successfully verified the effectiveness of the proposed method as well as the appropriateness of the theoretical analysis.

Application of Automatic Resonant Frequency Tuning Circuit to Induction Heating System

Koki Kamaeguchi, Kazuhiro Umetani, Eiji Hiraki

2018 20TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'18 ECCE EUROPE) 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Induction heating is the technique that heats the conductive material by high frequency large AC magnetic field. For efficient generation of the AC magnetic field, induction heating technique commonly utilizes the resonance between the heating coil and the resonating capacitor. The resonance is generally excited by applying the AC voltage of the resonant frequency. However, the resonant frequency is unstable because this frequency is susceptible to the disposition of the material to be heated. As a result, high efficiency high power induction heating system often suffers from unstable operation. This paper addresses this problem by proposing application of a simple automatic resonant frequency tuning circuit to the induction heating. This circuit can automatically achieve equivalent adjustment of the resonance frequency at the operating frequency without special control or the circuit sensing. In addition, this paper elucidated the control method of this tuning circuit to achieve the soft-switching operation in both of the inverter that drives the heating coil and the tuning circuit itself. The experiment revealed successful stabilization of the resonant frequency as well as satisfaction of the soft-switching condition both of the inverter and the tuning circuit, supporting effectiveness of the tuning circuit for induction heating.

High-frequency Self-Driven Synchronous Rectifier Controller for WPT Systems

Akihiro Konishi, Kazuhiro Umetani, Eiji Hiraki

2018 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-NIIGATA 2018 -ECCE ASIA) 1602 - 1609 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Resonant inductive coupling wireless power transfer (RIC-WPT) is the promising wireless power supply method to mobile applications. It is well-known that the efficiency and the power transfer capability of RIC-WPT systems deeply depend on the quality factor of the receiver-side resonator, which tends to decline by the conduction loss at rectifying diodes. Therefore, the synchronous rectification is one of the effective solutions. However, the unique characteristics of RIC-WPT, that is the weak magnetic coupling between the transmitter-side and the receiver-side resonator, tend to make the introduction of the synchronous rectification difficult. In order to address this issue, this paper newly proposes a self-driven synchronous rectifier controller suitable for RIC-WPT. This synchronous rectifier controller consists of basic analog elements and gate drivers, and no additional power supply is necessary for driving itself. In addition, the controller doesn't require any information from the transmitter-side resonator. Experiments successfully verified the operating principle as well as the efficiency improvement and clarified the usefulness of the synchronous rectifier with proposed controller for practical application of RIC-WPT.

Improving Robustness Against Variation in Resonance Frequency for Repeater of Resonant Inductive Coupling Wireless Power Transfer Systems

Masataka Ishihara, Shoma Ohata, Keita Fujiki, Kazuhiro Umetani, Eiji Hiraki

2018 20TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'18 ECCE EUROPE) 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Intermediate resonators (repeaters) for resonant inductive coupling wireless power transfer have been widely studied as a method of improving not only the transmission distance but also the output power. For the repeater to operate effectively, it is needed to induce a large current in the repeater to enhance the magnetic field far from a transmitting resonator. However, it is often difficult to induce a large current in the repeater due to frequency splitting phenomenon. This phenomenon easily occurs when the resonator having high quality factor such as the repeater is used. The frequency characteristic of the induced current in the repeater has multiple peaks when the frequency splitting phenomenon occurs. In addition, these multiple peaks shift according to slight variation in the parameters of the coil and the capacitor that constitute the resonator. This slight variation is easily caused by production error, temperature characteristic, and aging degradation of the coil and the capacitor. The induced current in the repeater is significantly decreased by the slight variation in the parameters, namely, the slight variation in the resonance frequency. Therefore, the repeater has low robustness against variation in the resonance frequency. To address these difficulties, we apply an auxiliary circuit to the repeater. The auxiliary circuit can dynamically adjust a phase of the induced current in the repeater, namely, the resonance frequency without complicated control. As a result, a large induced current can be maintained even if the frequencies corresponding to the peaks shift. Consequently, we can provide the repeater having a stable characteristic against the variation in the resonance frequency. The effectiveness of the repeater applied the auxiliary circuit and the appropriateness of analysis results are supported with simulation and experimental results.

Soft-Switching Control Circuit Based on Traveling and Reflected Waves for High -Frequency Resonant Inverter Applicable to Capacitive Load Impedance

Aoi Oyane, Koji Itakura, Kazuhiro Umetani, Eiji Hiraki, Tatsuya Ikenari, Shingo Kawano

IECON 2018 - 44TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY 3051 - 3056 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Resonant inverters are widely utilized to generate high-frequency high voltage AC power for the power supply to the plasma generator. These inverters commonly require the load impedance to be inductive for achieving soft-switching operation. However, the impedance often fluctuates to be momentarily capacitive due to the unstable state of the plasma, thus causing enormous switching loss and possibly destroying the inverters. This paper addresses this difficulty by using a recently-proposed resonant inverter that can achieve soft-switching operation under the capacitive load impedance. For this purpose, this paper proposes a novel soft-switching controller for applying this inverter for plasma generator application. The proposed controller observes the load impedance and controls the resonant inverter according to the impedance value. Because of the highfrequency AC power supply to the plasma generator, the voltage and current measurement are difficult for estimation of the load impedance. Therefore, the proposed controller estimates the load impedance based on traveling and reflected wave measurement. The experiment revealed successful control of the inverter according to the load impedance, suggesting high feasibility for applying the inverter to the plasma generator.

Extremum Co-Energy Principle for Analyzing AC Current Distribution in Parallel-Connected Wires of High-Frequency Power Inductors

Tomohide Shirakawa, Genki Yamasaki, Kazuhiro Umetani, Eiji Hiraki

IEEJ JOURNAL OF INDUSTRY APPLICATIONS 7 ( 1 ) 35 - 42 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：INST ELECTRICAL ENGINEERS JAPAN

Inductor winding is often comprised of parallel-connected wires to suppress copper loss. However, in high-frequency inductors, the proximity effect can cause concentrated AC current distribution, hindering the suppression of the copper loss. Therefore, optimization of the physical inductor structure requires predicting the AC current distribution caused by the proximity effect. Certainly, simulators have been commonly employed for predicting the AC current distribution. However, simple analytical methods are also required for efficient design or invention of inductor structures that have more uniform AC current distribution among the parallel-connected wires. The paper proposes a novel simple analysis method for AC current distribution in parallel-connected wires of high-frequency inductors. The proposed method is based on a novel insight that AC current is distributed to give an extremum of the magnetic co-energy contributed by the AC flux under the given total AC current. Analysis of basic inductor structures revealed that the proposed method can derive the AC current distribution by straightforward calculation. In addition, experiments supported the analysis results. Consequently, the proposed method is suggested to be promising for developing inductor structures with less copper loss.

DOI： 10.1541/ieejjia.7.35

Improved Thin Heating Coil Structure of Copper Foil Feasible for Induction Cookers

Kazuhiro Umetani, Tomohiro Mishima, Eiji Hiraki, Takayuki Hirokawa, Makoto Imai, Hideki Sadakata

IECON 2018 - 44TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY 3503 - 3508 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Litz wire is widely utilized for heating coils of the induction cookers to suppress the proximity effect. However, low space factor of the Litz wire often significantly increases the heating coil height, which may be an obstacle of wide-spread of the induction cookers. In order to overcome this problem, a preceding study has proposed a heating coil structure of the copper foil, which suppresses the proximity effect without using the Litz wire. The preceding study has proven effective suppression of the proximity effect, when the material to be heated is placed to cover the heating coil. However, this heating coil structure still suffers from large AC resistance, when the material to be heated does not exist or partially covers the heating coil. Furthermore, the ferrite walls, installed to suppress the proximity effect, need larger height than the coil, hindering effective reduction of the total heating coil height. The purpose of this paper is to propose an improved heating coil structure. The proposed heating coil structure further incorporates a thin layer of low-permeability soft-magnetic material covering the top of the coil. This layer enables elimination of the proximity effect regardless of the existence or the disposition of the material to be heated. Furthermore, this layer enables the ferrite walls to have the same height as the coil, thus further reducing the total heating coil height. The FEM based simulation was carried out to verify the operating principle of this structure. The result supported reduction of the heating coil height and effective suppression of the AC resistance regardless of the existence and the disposition of the material to be heated.

Design Optimization Method for the Load Impedance to Maximize the Output Power in Dual Transmitting Resonator Wireless Power Transfer System

Takahiro Koyama, Kazuhiro Umetani, Eiji Hiraki

IEEJ JOURNAL OF INDUSTRY APPLICATIONS 7 ( 1 ) 49 - 55 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：INST ELECTRICAL ENGINEERS JAPAN

Recently, the dual transmitting resonator wireless power transfer system (DTR-WPT) has been proposed as a promising technique for the power supply of mobile apparatus. Although this technique has been reported to be effective for increasing the output power as well as for covering a wide area during wireless power transfer, the complicated magnetic coupling among two transmitting resonators and one receiving resonator makes it difficult to develop practical design optimization methods, thus hindering practical applications of this technique. The purpose of this paper is to propose a design optimization method for the load impedance of DTR-WPT. This method is derived based on a novel simple equivalent circuit model of the DTR-WPT. The optimum impedance derived using this method as well as the appropriateness of the equivalent circuit were verified experimentally, thus validating usefulness of the proposed method for the practical application of DTR-WPT.

DOI： 10.1541/ieejjia.7.49

Theoretical Derivation of Phase Current Profile for Switched Reluctance Motors to Suppress Radial Force Ripple and Torque Ripple

Takayuki Kusumi, Takuto Hara, Kazuhiro Umetani, Eiji Hiraki

2018 IEEE 27TH INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS (ISIE) 1037 - 1042 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Switched reluctance motors (SRMs) are promising for propulsion motors of electric vehicles (EVs) because of their robust mechanical construction and cost effectiveness. However, practical application of SRMs to vehicular propulsion is hindered by comparatively large torque ripple and radial force ripple, which cause noise vibration and acoustic noise. Previous studies have proposed phase current profiles which suppress both ripples. However, in the derivation process of phase current, these previous studies need numerical calculation hindering the EV development speed. The purpose of this paper is to propose a novel phase current profile to suppress both the torque ripple and the radial force ripple of SRMs without numerical calculation. The profile can be straightforwardly calculated using a simple analytical model of the SRMs. In addition, the profile can be determined for any reluctance profiles of actual SRMs. Experiment was carried out to verify the proposed method. The result supported suppression of the torque ripple and the acoustic noise by the proposed method.

Rotor Configuration Which Reduces Copper Loss of Switched Reluctance Motors With Suppression of Torque Ripple and Input Current Ripple

Takayuki Kusumi, Takuto Hara, Kazuhiro Umetani, Eiji Hiraki

2018 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 6097 - 6103 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Switched reluctance motors (SRMs) are attractive motors for electric vehicle propulsion because of their cost-effectiveness or robust structures. However, SRMs suffer from input current ripple and torque ripple. The authors have proposed derivation method of phase current profile which suppresses input current ripple and torque ripple and experimentally verified the suppression of both ripples. However, the rms value of derived phase current was much greater than square wave current, which is implemented widely, and increased copper loss. For the EV application, the rms value should be reduced. To break through the issue, the author addressed the characteristic that phase current profiles are shaped based on each reluctance profile, which is shaped by motor configuration, and noticed that phase current profile with low rms value may be derived by a novel rotor configuration. Therefore, this paper proposes a novel rotor configuration which can reduce the copper loss. The proposed rotor configuration is designed to satisfy the reluctance profile which is derived by previously proposed derivation method of phase current. This paper also presents the experiment for the evaluation of the reduction of copper loss.

Verification of the Reduction of the Copper Loss by the Thin Coil Structure for Induction Cookers

Morimasa Hataya, Koki Kamaeguchi, Eiji Hiraki, Kazuhiro Umetani, Takayuki Hirokawa, Makoto Imai, Hideki Sadakata

2018 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-NIIGATA 2018 -ECCE ASIA) 410 - 415 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Litz wire is commonly employed as the heating coil of induction cookers. In order to realize further low cost and profile, the solid wire with simple construction and high space factor is required. However, the solid wire is may suffer from the large copper loss increased by the skin and proximity effect. Then, the previous study proposed the novel coil structure, which can suppress these effects, only by the FEM simulation. Therefore, the purpose of this paper is to verify this structure experimentally in comparison with the Litz wire coil. The result revealed that the proposed structure can have similar AC resistance and the similar height with the same surface area and the same number of turns. Moreover, the experimental result showed a possibility to further height reduction by optimization of the magnetic and winding isolation design. Consequently, the experiment supported practical effectiveness of the proposed structure for induction heating.

Feasibility Study of Fractal-Fin Heat Sink for Improving Cooling Performance of Switching Power Converters

Shogo Ikegami, Kazuhiro Umetani, Eiji Hiraki, Satoshi Sakai, Satoshi Higashino

2018 IEEE INTERNATIONAL TELECOMMUNICATIONS ENERGY CONFERENCE (INTELEC) 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Recent progress of the semiconductor switching devices enabled the high-frequency design of the switching power converters, which successfully led to the miniaturization of the circuit elements. However, the heat sink has scarcely been miniaturized during past decades. Now, the heat sinks are one of the major obstacles that hinder further size reduction of the switching power converters. Conventionally, the heat sinks are designed to have a number of flat aluminum fins extending from the aluminum base. However, these flat fins tend to make the laminar airflow passing through the fins. This laminar airflow keeps the air contacting the fin surface to remain on the surface. As a result, the fin surface is covered with the air already heated in the upstream and the fresh open air is prevented from contacting with the fin surface, thus deteriorating the cooling performance of the heat sinks. To overcome this issue, this paper proposes a heat sink structure with a novel fin geometry. The proposed fin geometry incorporates two sizes of the louvers, which are disposed to form a fractal-like pattern. These louvers are intended to break the laminar flow on the fin surface, thus promoting the mixing of the air to improve the cooling performance. FEM simulation of the heat transfer was carried out to verify this concept. The result showed improvement in the heat transfer coefficient, implying the effectiveness of the proposed structure for miniaturization of the heat sink.

Automatic Resonance Frequency Tuning Method for Repeater in Resonant Inductive Coupling Wireless Power Transfer Systems

Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

2018 INTERNATIONAL POWER ELECTRONICS CONFERENCE (IPEC-NIIGATA 2018 -ECCE ASIA) 1610 - 1616 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Intermediate resonator (repeater) in resonant inductive coupling wireless power transfer (RIC-WPT) systems can increase the transmission distance between the transmitting and receiving coils. The induced current in the repeater is easily affected by the frequency splitting phenomenon because the quality factor (Q-factor) of the repeater is generally as high as several hundreds. If this phenomenon occurs, induction of large current is often difficult in the repeater because the one peak characteristic of the induced current is no longer expected and the single peak of resonance splits into multiple peaks which shift the resonant frequency corresponding to the circuit parameters. In this paper, we approach this difficulty by applying an auxiliary circuit to the RIC-WPT system with the repeater. As a result, under the fixed operating frequency, the induced current in the repeater can be kept large even if the frequency splitting phenomenon occurs. The effectiveness of proposed system was supported by the simulation and experiment.

Straightforward Measurement Method of Common Source Inductance for Fast Switching Semiconductor Devices Mounted on Board

Kazuhiro Umetani, Kyota Aikawa, Eiji Hiraki

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS 64 ( 10 ) 8258 - 8267 2017年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Recent progress of widebandgap semiconductor switching devices enabled extremely high-frequency operation of power converters owing to their ultrafast switching capability. Fast switching may cause large switching noise at the common source inductance, which may increase the switching loss and lead to false triggering. Therefore, measurement of the common source inductance is often intensely required in practical design of fast switching power converters. However, measurement of the common source inductance is difficult, because 1) the wiring path hidden beneath the molded package significantly contributes to this inductance, 2) the mutual inductance between the gating circuit and the power circuit also contributes to this inductance, and 3) this inductance cannot be defined as the stray inductance of a loop wiring path. These difficulties are addressed in this paper by proposing a novel measurement method of the common source inductance. The proposed method is applicable to already-mounted power circuits. In addition, the proposed method offers a straightforward measurement procedure with common instruments, such as a signal generator, an oscilloscope, and voltage and current probes. Along with the measurement principle, this paper also presents an experiment to evaluate the proposed method.

DOI： 10.1109/TIE.2017.2694411

Novel receiving coil structure for improving efficiency and power transfer capability of resonant inductive coupling wireless power transfer 査読

T. Honjo, T. Koyama, K. Umetani, E. Hiraki

19th International Conference on Electrical Machines and Systems, ICEMS 2016 2017年1月

掲載種別：研究論文（国際会議プロシーディングス）

© 2016 The Institute of Electrical Engineers of Japan. Resonant inductive coupling wireless power transfer (RIC-WPT) is attractive as a convenient power supply method to small mobile apparatus. However, limited size of the receiving coil can limit the efficiency and the power transfer capability. This paper addresses this difficulty by proposing a novel receiving coil structure. The proposed structure has a coil wound on a drum core with a thin axis. The top and the bottom of the drum core has large surface area to effectively collect the magnetic flux for large mutual inductance. In addition, the thin axis can reduce the wire length, thus reducing the parasitic AC resistance. The AC resistance is further reduced by suppressing the proximity effect. Simulation supported probable improvement in the efficiency as well as the power transfer capability. In addition, experiment verified that the proposed structure improved the efficiency by 66% and the power transfer capability by 109%.

Novel thin heating coil structure with reduced copper loss for high frequency induction cookers 査読

M. Hataya, Y. Oka, K. Umetani, E. Hiraki, T. Hirokawa, M. Imai

19th International Conference on Electrical Machines and Systems, ICEMS 2016 2017年1月

掲載種別：研究論文（国際会議プロシーディングス）

© 2016 The Institute of Electrical Engineers of Japan. Litz wire has been widely utilized for heating coils of high frequency induction cookers. However, these coils often suffer from large winding height due to low space factor of Litz wire. Certainly, rectangular wire may reduce the winding height of the coil owing to its high space factor. However, the rectangular wire tends to suffer from large copper loss caused by the skin effect and the proximity effect. In the conventional coil structure of the rectangular wire, these effects cause concentrated AC current distribution, which leads to excessive copper loss. This paper addresses this issue by proposing a novel heating coil structure of the rectangular wire that can homogenize the AC current distribution. This paper also presents the simulation results that successfully verified the effectiveness of the proposed structure.

Optimization of the Balance between the Gate-Drain Capacitance and the Common Source Inductance for Preventing the Oscillatory False Triggering of Fast Switching GaN-FETs

Rynosuke Matsumoto, Kazuhiro Umetani, Eiji Hiraki

2017 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 405 - 412 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

GaN-FETs are attractive switching devices for their fast switching capability. However, they often suffer from the oscillatory false triggering, i.e. a series of self-sustaining repetitive false triggering induced after a fast switching. The purpose of this paper is to derive a design instruction to prevent this phenomenon. According to the previous study, the oscillatory false triggering was found to be caused by a parasitic oscillator circuit formed of a GaN-FET, its parasitic capacitance, and the parasitic inductance of the wiring. This paper analyzed the oscillatory condition to elucidate the design requirement to prevent the oscillatory false triggering. As a result, balancing the gate-drain parasitic capacitance and the common source inductance to achieve an appropriate ratio was found to be essential for preventing the oscillatory false triggering. Experiment successfully supported prevention of this phenomenon by balancing these two factors.

An Investigation into a Slight-Variation of the Transformer Effective Permeability in LLC Resonant Converter

Mostafa Noah, Shun Endo, Shota Kimura, Masayoshi Yamamoto, Jun Imaoka, Kazuhiro Umetani, Eiji Hiraki

2017 19TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'17 ECCE EUROPE) 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

In the LLC resonant converter, the transformer core is usually gapped to realize the designed value of magnetizing inductance that allows for soft switching. The air gap length which is in a scale of millimeters may be affected by the humidity and long working hours of the ferrite material, resulting into a variation of the core permeability. Moreover, a slight variation of the transformer core permeability may be encountered with any possible change in the core temperature. In a proper transformer design, the transformer shall operate with an optimum value of effective permeability where the sum of both copper and core losses is minimal. In this paper, the transformer optimal design is presented. Moreover, the influence of the permeability on the transformer's copper and core losses is revealed. Furthermore, with the help of newly derived equations, the effect of the transformer's effective permeability on the LLC converter conduction turn-on and turn-off losses is reported. Along with the theoretical discussion, the analysis is supported with simulation and experimental results utilizing a 250W-200kHz prototype.

Compact Three-Phase AC Inductor Network for PFC Converter Using Magnetic Coupled Technique

Takuya Ozaki, Hiroki Nakaido, Kazuhiro Umetani, Eiji Hiraki, Tatsuya Ikenari, Shingo Kawano

IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY 958 - 963 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Three-phase power factor correction (PFC) converters have been widely utilized in industrial power applications to improve the power factor and reduce current harmonics in three-phase power grid. The PFC converters commonly incorporate large-sized inductors as a noise filter to suppress the noise emission to the grid. However, as many other power converters, the PFC converters are intensely required to achieve high power density by reducing the size of the inductors. The purpose of this paper is to propose a magnetic structure to miniaturize the inductors. The proposed magnetic structure consists of an integrated magnetic component and a three-phase common-mode choke. By integrating the inductors, the proposed magnetic structure can miniaturize the magnetic core volume, while keeping the saturation current level and the noise filtering capability unchanged. Experiment was carried out to evaluate the appropriateness of the proposed magnetic structure as well as possible volume reduction. As a result, 32.2% volume reduction was found in the proposed magnetic structure without deterioration of the filtering capability.

Application of Extremum Co-Energy Principle for Homogenizing Current Distribution in Parallel-Connected Windings in Transformers: Design Optimization of Winding Turn Allocation among Winding Layers

Tomohide Shirakawa, Kazuhiro Umetani, Eiji Hiraki

2017 19TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'17 ECCE EUROPE) 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Parallel-connected windings are widely utilized for power transformers to reduce the copper loss. However, this reduction effect is often hindered by the proximity effect, which causes concentrated current distribution in parallel-connected windings. This paper addresses this issue by proposing a design optimization method of winding turn allocation among winding layers. This optimization method is based on the recently proposed insight on the proximity effect, referred to as the extremum co-energy principle. Experiment on a planar transformer with four primary winding layers was carried out to verify the proposed method. As a result, the proposed method successfully optimized the allocation of the winding turns to minimize the AC resistance.

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