Hitachi, Ltd.

Mitsuyoshi Hasegawa

Takashi Tsuboi

Hiroyuki Akiyama

Tadashi Kamada

Taro Uchii

A vacuum circuit breaker particularly suitable for use in an electric motor vehicle. The circuit breaker includes a vacuum interrupter to which a voltage is applied, the series combination of a capacitor and a switch which are connected in parallel with the vacuum interrupter, a provision for charging the capacitor with a voltage opposite the voltage applied to the vacuum interrupter, and a resistance connected in parallel with the vacuum interrupter. The vacuum interrupter, the resistance, and the series combination of the capacitor and switch form oscillation circuit having an oscillation frequency at least 2 KHz and an inductance of at least 1 .mu.H, with a commutating current of at least 5000 A for consuming energy stored in the circuit. In one embodiment, a capacitive element is connected in parallel with the resistor, and the length of the closed circuit include the vacuum interrupter and the capacitive element is shorter than the length of the closed circuit including the vacuum interrupter, the first capacitor, and the switch. Likewise, where no capacitive element is included, the length of the closed circuit including the vacuum interrupter and the resistance is shorter than the length of the closed circuit including the vacuum interruptor, the capacitor, and the switch. The resistance can be a linear or a nonlinear resistor, or the parallel combination of a linear resistor and a nonlinear resistor.

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Katsuta, Japan

Mitsuyoshi Hasegawa