Hitachi, Ltd.

Hitachi Metals, Ltd.

Noboru Ogawa

Kenichi Onda

Takashi Ikimi

Shigeta Ueda

Mitsuyuki Hombu

Shin Nakajima

Kohei Yabuno

Kenzo Kamiyama

Yorito Jifuku

Kozin Abe

A large capacity (1-2 MkVA) driving system for variable-speed-driving an AC motor by a power converter (inverter, converter) in which GTO (gate turn-off) thyristors are used as switching devices. In this system, high frequency GTO thyristors are connected in series, power converters are multiplexed, the AC motor is used in its plural phases, instantaneous spatial vector PWM (pulse width modulation) control is performed, vector control for the motor is performed, and a circuit for recovering snubber energy for GTO thyristors and a power factor adjusting circuit are provided. Thus, this driving system provides a torque ripple of 1% or less, speed response of 60 rad/sec or more, efficiency of 95% or more and a power factor of 98% or more.

Large capacity variable speed PWM spatial vector type sub-harmonic

A magnetically controlled switching regulator which controls an output voltage using a saturable reactor, wherein the saturable reactor is constituted by a first winding through which an output current flows and a second winding through which a reset current flows. The energy for resetting the saturable reactor is supplied from a capacitor in a smoothing circuit for an output voltage. A turn ratio between the first and second windings is set so that a sufficiently high reset voltage is obtained. Since the reset current of the saturable reactor does not flow through a transformer, the saturation of the transformer and a high increase in temperature thereof do not occur, so that the core of the transformer can be miniaturized and a high gain of the output voltage control circuit can be derived.

Switch mode power supply having magnetically controlled output

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Hitachi, Japan

Noboru Ogawa