Hitachi, Ltd.

Junko Shiozaki

Akira Bando

Shigehiro Kayukawa

Yasuteru Ohno

Toshio Taguchi

Junichi Shiozaki, Deceased

A control system for an AC excited synchronous machine for use in an electricity generator/motor system. The AC excited synchronous machine can be driven not only in a variable-speed operation based on 2-axis current control but also in a constant exciting frequency operation based on only direct-axis current component control. A phase signal is switched to drive stably the AC excited synchronoius machine in a self-excited operation or in a rotary phase modifying operation. Further, when it is desired to start pumping-up water, a synchronizing power is provided to keep constant the rotational speed of the machine at the time of establishing a desired water pressure. Because of the switching arrangement of the phase signal, the AC excited synchronous machine can be operated as an ordinary synchronous machine exhibiting ordinary synchronous characteristics, that is, self-excited operation characteristics, rotary phase modifying operation characteristics and pumping-up start characteristics. Even when the synchronous machine is cutoff from an AC power system and the voltage of the synchronous machine is abruptly changed, the stable self-excited operation of the machine can be realized.

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Hitachi, Japan

Junko Shiozaki