Hitachi, Ltd.

The Kansai Electric Power Co., Inc.

Shigehiro Kayukawa

Akira Bando

Hiroto Nakagawa

Yasuteru Oono

Osamu Nagura

Yosio Furukawa

Junichi Shiozaki

Sadahiko Niwa

Yasuteru Ohno

Tadaatsu Kato

Toshio Taguchi

Akira Momiyama

Junko Shiozaki

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.

System for controlling AC excited synchronous machine

An AC-excited generator/motor apparatus comprising; an AC-excited generator/motor having an armature mounting thereon; an armature winding connected to an AC power system and a rotor mounting thereon; and an exciting winding excited by an AC current. An exciting device for supplying a controlled AC exciting current to the exciting winding comprises; a device for calculating a real slip frequency based on a difference between the phase of an armature voltage appearing on the armature winding and the rotational phase of the rotor; and a device for controlling the exciting current supplied to the exciting winding from the exciting means in response to a deviation of the real slip frequency from a predetermined allowable range of slip frequencies so as to restore the real slip frequency within the allowable range of slip frequencies.

AC-excited generator/motor apparatus

A generator/motor system comprises a generator/motor having a primary winding and a secondary winding installed on the motor rotor coupled to a prime mover/load, a main circuit interposed between a power system and the primary winding of the generator/motor, an excitation circuit including a frequency converter inserted between a part of the main circuit and the secondary winding of the generator/motor, a frequency difference detector for determining the difference between the frequency of the power system and a frequency dependent on the rotational speed of the load, and a phase-shift control device for controlling the firing phase of the frequency converter in the excitation circuit by use of a signal from the frequency difference detector as a reference signal. In normal operation, a frequency signal following the frequency of the power system is produced, while at the time of a disturbance of the power system, the same frequency signal of the power system as before the disturbance continues to be produced thereby to keep the system in stable operation. For this purpose, a starting electric machine, a synchronous motor and a synchronous generator are aligned, and an output of the synchronous generator is applied to the frequency difference detector.

Variable-speed generator/motor system

Growing community of inventors

Hitachi, Japan

Shigehiro Kayukawa