I have related to superconductivity these thirty years. In the first stage, I have devoted to the control of the charge and discharge of a superconductive magnet, from the stand point of power electronics . Then belonging to the Research Center of Superconductivity, I have succeeded in the four quadrant P-Q control of the SMES. Meanwhile, the high temperature superconductivity (HTSC) was discovered. Hereafter, my colleague have discovered the mystery of HTSC by lighting the HTSC film.

View full abstract

High-Power RF supply is developed to drive the current of FRC (Field Reversed Configuration) plasma, which is one of nuclear fusion plasma configurations. By appling the rotating field that is brought by four antennas, plasma current in the toroidal dir ection would be enhanced. The power supply is consisted from the inverter circuit, the step-up tansformer and the LC tank ciruit. The tank circuit is the parallel circuit of the antenna and the capacitor. By the adjustment of the frequency of the inverter output to the resonance frequency of the tank circuit, the large sinusoidal waveform current is obtained.

View full abstract

This paper describes the experimental research and comparison on the characterristics of FRD used Epi layer wafer and Diffused wafer.
M. P. D. (Merged Pin Diode) construction which is composed of PiN diode and Schottky barrier diod is used in order to obtain fast and soft reverse recovery characteristics of 200V/300V/400V/600V rated reverse voltage.

View full abstract

For several years, the inverter generates AC 100V output voltage by obtaining DC12V from the cigarette lighter socket of the vehicle is beginning to spread in the market, and now the AC100V inverter system can be purchase not only in the car shop but also built in the vehicle by the car maker and car dealer. The AC100V inverter for vehicle is very useful in order to charge the battery of the laptop personal computer, cellar phone and PDA (Personal Digital Assistant) in outdoor and also very convenient for children to play TV game in the vehicle for long distance drive. However, almost all the type of the inverter for vehicle which can be buy in market or car dealer can not generate not pure sine AC100V wave but rectangle AC100V wave called “Modified Sine Wave”. This rectangle alternative voltage has possibility to give some problem to the electric appliances connected to the inverter. In this paper, the properties of various rectangle wave inverters were investigated experimentally, and the subject of the inverter was also clarified.

View full abstract

This paper presents an experiment for optimal current-control of permanent magnet synchronous motor, of which robust and simple current controller is designed without subjoining the estimating or lagging compensator, by analytical procedure of the inverse LQ design method. The ILQ design method is a strategy to find the optimal gains that is based on pole assignment without having to solve Riccati equation. By comparing with conventional PI control, it is quantitatively confirmed that the ILQ control is excellent in robust for variations of the motor's parameters. The results obtained give experimental verifications for simulation results which we had already reported.

View full abstract

This paper presents a new topology of the voltage source type bridge soft switching inverter circuit which proposes a novel active edge resonant snubber circuits using the auxiliary power switches. This advanced inverter is more suitable and acceptable for an uninterruptible power supply, such as PFC power converter, utility-interactive bi-directional power converter and new energy related distributed power supplies. The soft switching operation principle and design procedure of the active auxiliary edge resonant snubber circuit are described and discussed for the high power applications. Both the main active power switches and the auxiliary power switches achieve ZVS or ZCS for sinewave PWM inverter. This inverter does not need any sensor interfaced circuit to detect the voltage or the current and does not also required for the electrolytic chemical capacitors to make the neutral point of the DC power supply voltage side. This paper proposes a new gate timing pattern of switches in this soft switching inverter circuit, too. This method can limit the current of the active edge resonant snubber circuits lower than a level of the load current. As a result, the total efficiency characteristics of the converter system is improved high in all load range.

View full abstract

Linear synchronous reluctance motors (LSynRM) have many advantages, such as low cost being due to elimination of permanent magnets, easy recycling, and so on. But they need to have complex suspension mechanisms because of the large attractive force. Therefore the magnetic suspension system is adopted in this study. In magnetic suspension systems, two independent windings are generally used for the propulsion and the magnetic suspension.
In this paper the LSynRM with magnetic suspension using armature winding for propulsion is proposed.The characteristics of the LSynRM with double side stator are analyzed by using the finite element method (FEM), and we consider magnetically-levitated location detection and aim the development of magnetically-levitated system without sensor. The system stability of speed control method using d-q current adjustment is examined. As a resut, mover posision in the y direction is approximately constant without sensor and in spite of velocity change.

View full abstract

Recently, in refrigerator, reduction of power consumption is very important technology. Under such circumstances, the inverter control technology of a compressor contributed to reduction of power consumption greatly.
Now, as for inverter control of a refrigerator, the rectangle wave drive is mainly used. However, one of the disadvantages of this control is that the limit of an operating area is low. Consequently, when the efficient motor that increased the number of motor winding is driven, the maximum speed will be controlled further. Then we developed the method of extending the operation area of the motor under a rectangle wave drive. Consequently, operating without reducing the maximum speed of an efficient motor was realized.

View full abstract

[in Japanese]

View full abstract

The Discontinuous-Switching-Modulation (DSM) scheme has been developed and practically applied to the 3-phase Voltage-Source-Inverters to improve the dc-voltage utilization factor or to get a higher ac-output-voltage from a limited dc-voltage. On the other hand, the DSM is easily applicable to 3-phase Current-Source-Inverters/Rectifiers by referring to the Delta-Current-Modulation scheme that has been developed by one of the authors. This paper shows that the maximum controllable dc-voltage in the 3-phase Buck-type PFC rectifiers can be increased by 15% by means of the DSM and it has been confirmed through experimental results obtained from a 4kW class setup. Because of the maximum dc-voltage increase, the efficiency can be increased too and the fact has been confirmed experimentally. Additionally, the remaining problems/possibilities to be solved/explored in this project are discussed.

View full abstract