研究者詳細 - 平木　英治

論文 - 平木　英治

分割表示 309 件中 41 - 60 件目／全件表示 >>

Secondary-Side Center-Tapped Transformer Structure with One-Turn Secondary Coils Integrating Rectifier for Reducing Copper Loss of Forward Converter

Tomohide Shirakawa, Kazuhiro Umetani, Eiji Hiraki, Wilmar Martinez

2020 IEEE 29TH INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS (ISIE) 1459 - 1465 2020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

Secondary-side center-tapped transformer is a common transformer design of the high step-down forward converters owing to its effective reduction of the copper loss. Particularly, the extremely high step-down converters tend to have one-turn secondary coils to increase the winding turn ratio. However, due to the proximity effect in the terminal and the wire connecting the secondary coils and the rectifier, this design tends to suffer from significant deterioration of the copper loss reduction effect. To mitigate this problem, this paper proposes a novel transformer's secondary-side structure that integrates the one-turn secondary coils and the rectifier. The proposed transformer structure can mitigate the proximity effect in the secondary coils and the rectifier, thus suppressing the local concentration of the current distribution. Experiments revealed effective reduction of the copper loss, supporting the effectiveness of the proposed structure.

Competition-Based Learning of Power Converter Design Emulating Product Development Activity

Kazuhiro Umetani, Eiji Hiraki

IECON 2020: THE 46TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY 3339 - 3344 2020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

Power conversion technology is characterized by the comparatively small variation of circuit topologies. Because product competitiveness mainly lies in the performance quality as efficiency and low noise emission, the professional skills of this technology commonly require the ability to improve the quality under the restriction of the space, the material resource, and the cost. The conventional teaching method of the power conversion technology is mainly based on the lecture classes and the hands-on classes, which teach the fixed knowledge of the circuit operation. Therefore, this conventional method tends to be insufficient to cover the various practical strategies to improve the quality. To overcome this difficulty, this paper proposes application of the competition-based learning (CBL), in which teams of the students design their power converters and compete on the efficiency. For many professional engineers, competition among companies is the basic motivation to think of strategies to improve product competitiveness. Therefore, the CBL may be effective for teaching design strategies. For promotion of sharing the know-how, the proposed teaching method introduces the events, in which each team share its design strategies with other teams and improve its design based on the know-hows of other teams These events emulate the economic activity, in which a company investigates its competitors' products to extract the know-how. Along with the basic methodology of the proposed teaching method, this paper also reports the experience of a teaching course.

Optimization of Common Source Inductance and Gate-Drain Capacitance for Reducing Gate Voltage Fluctuation after Turn-off Transition

Yusuke Hatakenaka, Kazuhiro Umetani, Masataka Ishihara, Eiji Hiraki

2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 3155 - 3162 2020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

Next-generation switching devices as GaN-FETs are recently emerging as promising switching devices capable of extremely high-speed switching. High-speed switching enables the high-frequency operation of the power converters, which can reduce the size of the passive components. However, highspeed switching can induce the resonance between the parasitic capacitance of the switching device and the parasitic inductance of the circuit board wiring, which appears as the gate voltage fluctuation at the switching. Particularly, GaN-FETs tend to have comparatively low gate threshold voltage and therefore are susceptible to the false turn-on, which is caused by the gate voltage fluctuation in the switching device just after the turn-off transition. For preventing this phenomenon, this paper analytically investigates the design requirement of these parasitic parameters to reduce the gate voltage fluctuation after the turn-off transition. As a result, the optimal ratio of the gate-drain capacitance and the common source inductance is elucidated to be the key to minimize the gate voltage fluctuation. The simulation and the experiment supported that the optimal design of this ratio can reduce the gate voltage fluctuation, supporting the usefulness of this novel insight for preventing the false turn-on.

Analysis and Prediction of AC Resistance of Litz Wire with Rectangular Cross-Section

Shota Kawahara, Kazuhiro Umetani, Eiji Hiraki

2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 3273 - 3279 2020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

The Litz wire is widely utilized in recent high frequency switching regulators as a magnetic wire with small AC resistance. The AC resistance of the Litz wire is dependent on the twisting structure of the strands as well as the resultant cross-section geometry of the Litz wire. Therefore, optimization of the Litz wire is becoming important, although the numerical prediction of the AC resistance is difficult due to the complicated structure of the Litz wire. Certainly, a recent study has proposed an analytical AC resistance prediction method. However, this method cannot be applied to Litz wires with the rectangular cross-section, which is recently developed to improve the packing factor of the winding. This paper aims at extending this previous method to cover these Litz wires by partly utilizing a simple static magnetic field FEM analysis. The experiment revealed successful AC resistance prediction of the Litz wire with the rectangular cross-section.

Multiple-Transmitter Achieving Load-Independent Transmitter Current and Compensation of Cross-Interference Among Transmitters for Wide Charging Area Wireless Power Transfer Systems

Kodai Matsuura, Masataka Ishihara, Akihiro Konishi, Kazuhiro Umetani, Eiji Hiraki

2020 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 5474 - 5481 2020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

Recently, a resonant inductive coupling wireless power transfer (RIC-WPT) system with multiple transmitters is emerging as a promising power supply method for household appliances, mobile devices, and wearable devices dispersedly placed in a wide area. However, the multiple-transmitter often suffers from an unstable operation of an inverter, feeding AC current to the transmitter coil, due to the cross-interference (i.e., cross-coupling) among the transmitters. When the cross-interference occurs, the inverter may not achieve high power factor and soft switching, which damages the power density and reliability of the multiple-transmitter. Therefore, this paper proposes a multiple-transmitter, including its controller, that can compensate for the effect of the cross-interference. In the proposed multiple-transmitter, each transmitter has a simple switching circuit that can automatically cancel the induced voltage due to the cross-interference with only simple control. Furthermore, the proposed multiple-transmitter also achieves a load-independent transmitter current by the control of the input voltage of the inverter, which results in a stable magnetic field regardless of load variation. Experiments verify the effectiveness and appropriateness of the proposed multiple-transmitter.

Homogenization of Current Distribution in Parallel Connection of Interleaved Winding Layers of High-Frequency Transformers by Optimizing Distance between Winding Layers

Ryo Murata, Tomohide Shirakawa, Kazuhiro Umetani, Eiji Hiraki, Hiroto Mizutani, Takaaki Takahara, Osamu Mori

2020 22ND EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'20 ECCE EUROPE) 2020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

The windings of high-frequency high-current transformers are required to reduce the proximity effect loss. Therefore, the Litz wire in parallel connection of interleaved winding layers is usually used as the winding of transformers. However, this can cause unbalanced AC current distribution, hindering effective reduction of the copper loss. This paper solves this problem by optimizing the distance between the winding layers based on the analytical principle called the extremum co-energy principle. The transformers used in the experiment to verify this method consists of three parallel-connected primary winding and two parallel-connected secondary winding, PQ core, thin polypropylene sheets for adjusting the distance between the winding layers. As a result, the copper loss can be recused by homogenizing the AC current distribution, and the effectiveness of this method has been clarified by experiments.

Receiving-coil structure reducing stray AC resistance for resonant coupling wireless power transfer

Kazuhiro Umetani, Toru Honjo, Takahiro Koyama, Masataka Ishihara, Eiji Hiraki

IET POWER ELECTRONICS 12 ( 9 ) 2338 - 2344 2019年8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：INST ENGINEERING TECHNOLOGY-IET

Resonant inductive coupling wireless power transfer is widely known to be a possible convenient power supply method for the small mobile apparatus. However, the limited receiving-coil size tends to lower the efficiency and limit the output power owing to the small mutual inductance and comparatively large stray alternating current (AC) resistance of the receiving-coil. This study mitigates this issue by proposing a novel receiving-coil structure. This proposed structure comprises a coil and a drum core with a thin axis. The coil is wound on the axis to form a single winding layer. The proposed structure can reduce stray AC resistance by suppressing the proximity effect and reducing the wire length without deteriorating the mutual inductance significantly. Therefore, better efficiency and larger output power can be achieved. Simulations and experiments were performed to verify the proposed structure. Consequently, both simulations and experiments supported the reduction in AC resistance compared to the conventional structure. Furthermore, the experiment revealed improvements by the proposed structure in both efficiency and output power. These results support the effectiveness of the proposed structure for wireless power transfer to small mobile apparatus.

DOI： 10.1049/iet-pel.2018.5358

Volume Reduction Effect of Thinly Extended Core Structure for Transformer in Isolated DC-DC Converter 査読

R. Murata, T. Shirakawa, K. Umetani, E. Hiraki

ICPE 2019 - ECCE Asia - 10th International Conference on Power Electronics - ECCE Asia 2132 - 2138 2019年5月

掲載種別：研究論文（国際会議プロシーディングス）

© 2019 The Korean Institute of Power Electronics (KIPE). The high-frequency transformers used for isolated DC-DC converters tend to have large volume compared with the other components. Therefore, increasing the power density of the transformer is indispensable for increasing the power density of the DC-DC converter. Reducing the dead space of the transformer is one of the effective solutions. It is well-known that the thinly extended core structure reduces the dead space around the transformer formed by the windings protruding to the outside of the core. However, it has not been clarified how much the thinly extended core structure affects the reducing power loss of the transformer. In this paper, the effect of introducing the thinly extended core structure into the transformer is quantified by the optimization of the convertible design parameters of the transformer with systematic round-robin calculation. The result revealed the volume reduction effect by the thinly extended core was greater than the simply dead space reduction effect.

Prevention of Oscillatory False Triggering of GaN-FETs by Balancing Gate-Drain Capacitance and Common-Source Inductance

Kazuhiro Umetani, Ryunosuke Matsumoto, Eiji Hiraki

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS 55 ( 1 ) 610 - 619 2019年1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

Gallium-nitride-field-effect transistors (GaN-FETs) are promising switching devices with fast switching capability. However, they commonly have low gate threshold voltage, suffering from susceptibility to the false triggering. Particularly, the oscillatory false triggering, i.e., a self-sustaining repetitive false triggering, can occur after a fast switching, which is a severe obstacle for industrial applications. The purpose of this paper is to elucidate the design instruction for preventing this phenomenon. The oscillatory false triggering is known to be caused by the parasitic oscillator circuit formed of a GaN-FET, its parasitic capacitance and the parasitic inductance of the wiring. This paper analyzed the nonoscillatory condition of this oscillator. The result revealed an appropriate ratio between the gate-drain capacitance and the common-source inductance is a key to prevent the oscillatory false triggering. Experiment successfully verified this analysis result, supporting the effectiveness of the appropriate design of this ratio for preventing the oscillatory false triggering.

DOI： 10.1109/TIA.2018.2868272

Automatic Active Compensation Method of Cross-Coupling in Multiple-receiver Resonant Inductive Coupling Wireless Power Transfer Systems

Masataka Ishihara, Keita Fujiki, Kazuhiro Umetani, Eiji Hiraki

2019 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 4584 - 4591 2019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

The ability to charge to multiple receivers simultaneously with a single transmitter is one of the advantages of resonant inductive coupling wireless power transfer (RICWPT) technologies. However, in multiple-receiver RIC-WPT systems, each receiver often suffers from the magnetic coupling among receivers, i.e., cross-coupling. The cross-coupling not only complicates the control of the receivers but also significantly decreases the output power of each receiver. Hence, the purpose of this paper is to propose a compensation method of the influence due to the cross-coupling. To achieve this purpose, we first analyze the requirement to compensate for the influence of the cross-coupling. As a result, we reveal that it is necessary to control the phase of the current in all the receiver to be orthogonal to the phase of the transmitter current. Then, we propose the method to adjust the current phase of each receiver automatically to the desired phase by using only the phase information of the transmitter current, which results in the full compensation of the influence due to the cross-coupling. Furthermore, the proposed method also compensates for the influence of a detuning of the resonant frequency of each receiver due to the natural tolerance. Experiments of a two-receiver RIC-WPT system successfully verify the effectiveness of the proposed method.

Resonant Frequency Tuning System for Repeater Resonator of Resonant Inductive Coupling Wireless Power Transfer

Akihiro Konishi, Keita Fujiki, Kazuhiro Umetani, Eiji Hiraki

2019 21ST EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE '19 ECCE EUROPE) 2019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

The resonant inductive coupling wireless power transfer (RTC-WPT) is a promising technique of the wireless power transfer with comparatively large power and high efficiency. However, the performance of RTC-WPT system is generally highly dependent on the fine adjustment of the resonant frequency between the transmitter, receiver, and repeater resonators, although the natural tolerance of the capacitor and inductance of the coil may easily lead to the significant detuning of the resonant frequency. Particularly, the repeater resonator is the key item that can improve the power transfer to a distantly located receiver resonator. However, the repeater resonator tends to have a high quality-factor; and therefore, its performance can be easily deteriorated by the detuning of the resonant frequency. The purpose of this paper is to propose a simple automatic resonant frequency tuning system for the repeater resonator as a remedy for the performance deterioration due to the resonant frequency detuning. The operation of the automatic resonant frequency tuning system was experimentally tested using the prototype wireless power transfer system. The result exhibited robust power transfer capability regardless of the natural tolerance of the resonant frequency.

Core Loss Modeling Based on Equivalent Circuit for Switched Reluctance Motors

Takayuki Kusumi, Kosuke Kobayashi, Takuto Hara, Kazuhiro Umetani, Eiji Hiraki

2019 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT) 1743 - 1748 2019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

To estimate the core loss in SRMs, core loss estimation by equivalent circuit is preferable especially in the EV development because of its simple calculation. However, previously proposed models may limit applicable operating condition. These models refer instantaneous value, whereas hysteresis loop is a key factor to estimate core loss and the hysteresis loop directly associates with the history of magnetic flux. This paper focuses on the relation between the width of hysteresis loop and the peak to peak value of magnetic flux because the relation directly expresses the core loss. Therefore, the purpose of this paper is to propose a novel core loss model for equivalent circuit which estimates core loss in SRMs. This paper refers the peak to peak value of magnetic flux linkage and electrical angle. Along with the theoretical formulation of the model, this paper presents the model construction method. As a result, the proposed model successfully estimated core loss.

DOI： 10.1109/ICIT.2019.8754931

Analytical Derivation of Phase Current Waveform Eliminating Torque Ripple and Input Current Ripple of Switched Reluctance Motors under Magnetically Saturated Operation

Takayuki Kusumi, Kosuke Kobayashi, Kazuhiro Umetani, Eiji Hiraki

2019 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 6540 - 6547 2019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) is beneficial in excellent cost-effectiveness and high thermal tolerance owing to their simple mechanical construction free from permanent magnets. Nevertheless, application of SRMs to vehicular propulsion is often hindered by their comparatively large input current ripple and torque ripple. For mitigating the problem, the previous study has proposed a phase current waveform that eliminates both of these ripples under the magnetization below the magnetic saturation. However, this previous technique still suffers from significant torque and input current ripples at large output torque, which tends to cause the magnetic saturation. This paper proposes an improved phase current waveform that eliminates these ripples even at large output torque. This waveform was derived analytically based on the nonlinear magnetic model of the SRM. The proposed phase current waveform was successfully verified by the experiment, suggesting the usefulness of the proposed technique for applying SRMs to vehicular propulsion.

Experimental Verification of Impedance Matching Method for Repeater to Improve Spatial Freedom of 6.78 MHz Resonant Inductive Coupling Wireless Power Transfer Systems

Keita Fujiki, Masataka Ishihara, Kazuhiro Umetani, Eiji Hiraki

2019 21ST EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE '19 ECCE EUROPE) 2019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

Placing a repeater, which relays the magnetic field from the transmitter to the receiver, is promising as a method to increase the spatial freedom of resonant inductive coupling wireless power transfer systems (RTC-WPT) working at 6.78MHz. However, the capability of the repeater is often affected by a frequency splitting phenomenon. When this phenomenon occurs, the resonance in the repeater becomes sufficiently small at a fixed operating frequency and make it difficult to improve the spatial freedom. To solve this problem, we apply an impedance matching method using simple switching circuits to the 6.78 RTC-WPT system with the repeater. Then we carry out experiments to verify the effectiveness of the impedance matching method. The experimental results show that the repeater improves the spatial freedom of the 6.78 MHz RTC-WPT regardless of the frequency splitting phenomenon.

Simple Fully Analytical Copper Loss Model of Litz Wire Made of Strands Twisted in Multiple Levels

Kazuhiro Umetani, Jesus Acero, Hector Sarnago, Oscar Lucia, Eiji Hiraki

THIRTY-FOURTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC 2019) 1257 - 1264 2019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

The Litz wire has been widely utilized as a wire with a low copper loss under high-frequency operation. However, design optimization of the Litz wire is difficult because this wire generally has a complicated structure of thin strands twisted in multiple levels, which hinders both of the analytical and numerical prediction of the copper loss. To overcome this issue, recent studies have proposed the analytical models of the copper loss in the bundle of twisted strands, which is the basic components constituting the Litz wire. This paper constructs a simple analytical copper loss model of the Litz wire based on these preceding insights. In addition to these insights, the proposed model further considers the effect of the inclination angle of the strands to the Litz wire on the proximity effect loss. The proposed model was tested in comparison with the experimentally measured AC resistance of commercially available Litz wires. As a result, the predicted AC resistance showed good agreement with the measured ac resistance, suggesting the effectiveness of the proposed model.

Effects of Secondary Leakage Inductance on the LLC Resonant Converter-Part I: Transformer Voltage Gain and Efficiency

Mostafa Noah, Tomohide Shirakawa, Kazuhiro Umetani, Jun Imaoka, Masayoshi Yamamoto, Eiji Hiraki

THIRTY-FOURTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC 2019) 780 - 786 2019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

Minimizing the transformer magnetizing inductance is essential for the soft switching operation of the LLC resonant converter, despite the fact that it results in higher values of magnetizing current, which deteriorates the converter efficiency. Furthermore, it is a well-known practice to utilize the transformer leakage as an inductive component in the resonant tank to improve the power destiny. This paper reveals that the transformer voltage gain can be improved when the transformer leakage inductance in concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current (i.), especially at light load condition. The theoretical discussion relies on the asymmetry of the EI core by placing the secondary winding in a close contact with the magnetic core and placing the primary winding in the vicinity of the air gap. Moreover, noise absorber had been utilized to control the leakage inductance value. The proposed transformer design maximizes the value of the secondary leakage inductance and minimizes the primary leakage inductance. Alongside with the theoretical discussion, experimental tests had been conducted to evaluate the proposed method using a 390V-12V, 220W LLC resonant converter.

Effects of Secondary Leakage Inductance on the LLC Resonant Converter-Part II: Frequency Control Bandwidth with respect to Load Variation

Mostafa Noah, Tomohide Shirakawa, Kazuhiro Umetani, Jun Imaoka, Masayoshi Yamamoto, Eiji Hiraki

THIRTY-FOURTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC 2019) 1408 - 1414 2019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 converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

Optimal Winding Layer Allocation for Minimizing Copper Loss of Secondary-Side Center-Tapped Forward Transformer with Parallel-Connected Secondary Windings

Tomohide Shirakawa, Kazuhiro Umetani, Eiji Hiraki, Yuki Itoh, Takashi Hyodo

2019 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE) 6206 - 6213 2019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

Secondary-side center-tapped transformers are widely utilized for high step-down forward DC-DC converters. For reducing the copper loss, optimization of the winding layer allocation can be a promising approach. However, the optimal allocation pattern has been difficult to be elucidated, particularly if the winding is formed of parallel-connected winding layers or carries the AC and DC current as in a center-tapped winding. This difficulty is addressed in this paper by proposing a copper loss analysis method applicable to parallel-connected winding layers and a center-tapped winding. The proposed analysis method utilizes the Dowell method in combination with the extremum co-energy principle, which has been recently proposed to analyze the current distribution in parallel-connected winding layers. As an example, this paper analyzes the center-tapped transformer each secondary winding of which is made of two parallel-connected winding layers. The optimal winding layer allocation pattern was elucidated by comparing the copper loss among six possible winding layer allocation patterns. Appropriateness of the analysis was verified by simulation, suggesting the effectiveness of the proposed method and the importance of optimizing winding layer allocation in the forward transformer design.

Axial Heating Coil Structure for Reducing Magnetic Levitation Force of All-Metal Type Induction Cookers

Koki Kamaeguchi, Kazuhiro Umetani, Eiji Hiraki

2019 8TH INTERNATIONAL CONFERENCE ON RENEWABLE ENERGY RESEARCH AND APPLICATIONS (ICRERA 2019) 793 - 798 2019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

All-metal type induction cookers are utilized to heating up the non-iron pans such as the copper and aluminum pans. These cookers are designed to drive the heating coil with extremely high frequency and large AC current. However, the high-frequency large current drive tends to generate a large electromagnetic force which has the direction levitating the pans to be heated and damages the safeties of the induction cooking by moving the hot pans. The purpose of this study is to propose a novel heating coil structure that can reduce the levitation force. The proposed structure coil is similar to the axial gap induction machine. This coil structure generates the electromagnetic force in parallel to the coil surface rather than perpendicular to the surface, thus mitigating the levitation force. In addition, a novel AC power supply is proposed to drive the proposed structure coil. The experiment revealed a successful reduction of the levitation force by approximately 20% compared to the conventional coil structure, supporting the effectiveness of the proposed coil structure.

Verification of Device Model by Measuring Capacitance and Static Characteristics for Predicting Switching Waveform

Kengo Koki, Masahiko Yoshioka, Kazuhiro Umetani, Eiji Hiraki

2019 8TH INTERNATIONAL CONFERENCE ON RENEWABLE ENERGY RESEARCH AND APPLICATIONS (ICRERA 2019) 786 - 792 2019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

Recently, as the miniaturization and densification of the power conversion circuit, switching frequency has been increased. To accomplish the densification, it is essential to predict the losses that occur in each part for the optimization of electric components. However, switching loss which needs to consider nonlinear characteristics are difficult to predict. As a solution, considering the dependence of the gate-drain capacitance on gate-source voltage may improve the prediction accuracy of switching loss. The purpose of this study is to evaluate the improvement of prediction accuracy by considering it. First, to construct the simulation model, the wiring parameter in the circuit, static characteristics and the parasitic capacitance of the device was measured. Next, the device model provided by the manufacturer to use in the simulation was adjusted. Also, the characteristics of the gate-drain capacitance on the gate-source voltage were obtained from two types of measurement circuits. As a result, it was verified that the difference which occurred at the rise of the drain-source voltage at the turn-off tended to decrease and prediction accuracy of the turn-off loss was improved by considering the characteristics of the gate-drain capacitance on the gate-source voltage. Therefore, we concluded that this consideration has the ability to the improvement of turn-off waveforms.

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