Evolution in power electronics is expected by the development of wide-gap semiconductors, since present-day silicon (Si)-based power devices are not enough in future because of the limit of its inherent properties. High-quality epitaxial growth of silicon carbide (SiC) and its superior electrical properties are introduced. The state-of-the art SiC power devices utilizing high-quality epi-layers are reviewed.

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This paper presents the results of experimental study on the effects of synchronization systems for a thyristor controlled series capacitor (TCSC). A comparison has been made between two different synchronization schemes: synchronization with respect to zeros of TCSC capacitor voltage and synchronization with respect to zeros of line current. No such comprehensive investigation has been reported in the literature yet. A laboratory-scale TCSC has been designed, produced and installed in a laboratory power system at Kyoto University. Effects of the two synchronization systems on the performances of TCSC have been investigated on the experimental system. Steady-state impedance characteristics, dynamic response, and instability of TCSC in a variety of operating conditions have been compared. Both advantages and disadvantages of the two synchronization systems have been clarified.

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Characteristics of power semiconductor devices such as Power MOSFETs, IGBTs and Thyristors at cryogenic temperature were examined by experiments and computer simulations using 2-Dimensional models. Power MOSFETs showed excellent characteristics at 80K. NPT (Non-Punch Through) IGBTs will show better characteristics than PT (Punch Through) IGBTs at cryogenic temperature. Thyristors can be operated, although on-voltage increases at cryogenic temperature.

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We have developed and proposed a novel active filter system composed of inverter bypass circuit for suppression of harmonic resonance condition caused between the inductance behind the load bus and the capacitance of var equipment especially at lower harmonic frequencies.
We have installed this new scheme of harmonic compensation system in combination with TCR-type SVC and shunt LC filters at the Yamanashi Maglev Test Line.
We will describe the outline of the reactive power and harmonic compensation systems, and harmonic resonance test results which show satisfactory performance of the active filter.

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Synchronous reluctance motor (SynRM) is superior in maintenance, generates few heat in the rotor and suits high-speed drive, because it has no winding and magnet in rotor. Recently, SynRM is drawing the attention. Therefore many designs of the rotor are proposed. In this paper, we examine a synchronous reluctance motor with multi-flux barrier. Firstly, the structure of motor is discussed. Secondly, analytical results of flux distribution and characteristics of SynRM are shown. Finally, the experimented results of prototype motor are discussed.

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Recently the capacity of the Automatic Washing Machine has grown so large and the silent operation has become the main current of the mar ket requirement. For the solution of these two disagreed problems, we applied the Inverter Control System to the 3-phase Brushless DC Motor. Consequently we have reallized the few damage operation and the save energy as half of the usual input power by the spin speed, cycle time and the operation time of the pulsator which is most suitable for each clothes.
Inverter control unit is consist of the parts showed Fig. 1.
We developped the new Intelligent Power Module (IPM) which includes 6-IGBT and their power supply circuit. We used the Bootstrap circuit in the power supply circuits in order to reduce 4 to 1 power supply circuit so we have made IPM small. We designed the frequency of Inverter Switching over 15kHz in order to reduce the noise level. The Inverter control Unit and the operation unit are separated and 2 microcomputors of each unit are intercommunicated with the sirial data.

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This paper expresses a circuit simulation of the utility interactive inverter on a photovoltaic system that supplies the utility source with the power generated by solar sells. We realize the inverter circuit works as a complete current type inverter has an immittance conversion link with a high frequency insulation transformer.
Characteristics of this utility interactive inverter are as follows. The inverter output current is in proportion to only PWM output voltage of the high frequency inverter, independent of the amplitude or the waveform of the utility source voltage. The inverter output current to the utility source can be controlled easily, and can be maintained the reference value with very fast response even if the utility voltage changes sharply.

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This paper deals with leakage current, line current and the high-frequency equivalent circuits in an induction motor driven by a PWM inverter. These currents flow through stray capacitances between stator windings and iron core (frame) of the induction motor at the switching instants of the inverter transistors. The high-frequency equivalent circuits are derived based on the frequency characteristics of the high-frequency zero-phase-impedance and line-to-line-impedance of the induction motor. The validity of the derived equivalent circuits is confirmed by simulation and experimental results.

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This paper presents a high-frequency load resonant IGBT inverter with a series-compensated resonant inductor and high-voltage transformer for silent discharge ozonizer power supply which is designed so as to be operated under a principle of Pulse Density Modulation (PDM) strategy. This type of inverter is evaluated on the basis of the circuit modeling of the silent discharge-based ozone generating tube and high-frequency transformer. It is noted that the pulse density modulated load resonant high-frequency inverter using IGBTs makes an ozonizer power control scheme simple and efficient as well as this control procedure can improve the ozone generating characteristics. Thus, it is more effective to increase the ozone producing efficiency. Finally, it is proved that the load-resonant inverter type PDM controlled ozonizer developed in this paper can provide stable and efficient silent discharge characteristics over a wide output power range from 10% to 100%.

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In this paper the current fed inverter with IGBT (Insulated Gate Bipolar Transistor) & the voltage fed inverter with P. MOSFET (Power Metal-Oxied Semiconductor Field Effect Transistor) are presented. The current fed inverter uses IGBT as a switching device in the combination of series & muiti-parallels strings to increase the permissible current & voltage, then 1, 000kW-50kHz can be realized on which method is met to the requirement of high power out-put. The voltage fed inverter uses P. MOSFET as a switching device, then 1, 000kW-200kHz is realizes from the structure of module units. The obtained power 100kW per module, can be met to the requirement of high power out-put as well. An actual usage of examples for Induction heating application are shown.

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