Hitachi, Ltd.

Ryuji Iyotani

Hidetoshi Aizawa

Masahiro Nagasu

Shuji Katoh

Hiromitsu Sakai

Atsumi Watanabe

Mitsuyuki Hombu

Hiroshi Narita

Hisao Amano

Akiteru Ueda

Fumio Ogata

A semiconductor power converting apparatus includes a semiconductor element for controlling a current flowing between a collector and an emitter in response to a gate condition, a driving device connected to the gate, for driving the gate in response to a drive signal entered thereinto, a voltage applying device for applying both a forward bias and a reverse bias to the gate so as to set the emitter of the semiconductor element to a neutral potential, and a voltage dividing device for dividing a voltage appearing between the collector and the emitter of the semiconductor element, in which the drive signal is under OFF state, a voltage produced based upon the divided voltage by the voltage dividing device is applied to the gate, and the gate voltage is controlled in response to the voltage appearing between the collector and the emitter of the semiconductor element, thereby reducing the snubbed loss.

Semiconductor power converting apparatus

An electric power converter comprising a plurality of reactors, a plurality of self quenching type switching elements, the reactors and switching elements being series-connected per one arm, and surge-absorbing snubber circuits connected in parallel to the switching elements respectively, the switching circuits being driven by gate drive circuits connected to respective gates of the switching elements to thereby convert a DC voltage into an AC voltage or convert an AC voltage into a DC voltage. The electric power converter further comprises: an apparatus for recovering energy accumulated on at least one side of the reactors and the snubber circuits and an apparatus for generating a DC source for supplying electric power to each of the gate drive circuits, on the basis of the recovered energy. In the electric power converter constituted by a plurality of self quenching type semiconductor switching elements connected in series, high efficiency is attained through reduction in size of the gate driver and electric power saving.

Gate drive power source for electric power converter

A thyristor valve includes a plurality of thyristors connected in series and series circuits each including a capacitor and a resistor and connected in parallel with each thyristor. A pulse from a pulse generator for firing the thyristors is applied to them at the beginning of a prescribed period of conduction of the thyristor valve when voltage across the selected one of the thyristors is forward. An output signal of a current detector provides a firing pulse to all thyristors when the valve current exceeds a predetermined current value during the prescribed period of conduction of the thyristor valve.

Gate controlling apparatus for a thyristor valve

A gate controlling apparatus for a thyristor valve including a plurality of series connected thyristors controlled by a narrow gate pulse. The apparatus includes means for judging whether the thyristor valve is to be in the conductive state or not, means for detecting a forward voltage across at least one of the thyristors in the thyristor valve, and an AND circuit for generating an output at a time when an AND condition between the respective outputs of the judging means and the forward voltage detector means is satisfied. The apparatus further includes means for detecting a period of inverse voltage across at least one of the thyristors in the thyristor valve. The forward and inverse voltages may be, respectively, detected by detecting the forward and inverse voltages of specified thyristors.

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Hitachi, Japan

Ryuji Iyotani