Mutual Interaction between Zero-Phase-Sequence and Negative-Phase-Sequence Circuits in a Synchronous Generator

Abstract

The mutual interacton between zero-phase-sequence and negative-phase-sequence circuits in a salient pole synchronous generator is proved experimentally and theoretically. In the method of symmetrical coordinates, it has been believed that positive-, negative- and zero-phase-sequence components are independent. But an experiment driving a synchronous generator with unbalanced load shows that negative-phase-sequence voltage is induced when only zero-phase-sequence current is applied. These interaction between negative- and zero-phase- sequence circuits are proved theoretically by magnetic flux distribution in the air-gap of synchronous generator. The m. m. f. by zero-phase-sequence current generates negative-phase-sequence flux distribution by the saliency of the rotor and the field current 2nd harmonics and vice versa. The revised exprssion for synchronous machine in the symmetric coordinate is proposed.