Identification of Element-Values in the Equivalent Circuit of Synchronous Machine

Method by Approximate Expression of D. C. Decaying Curren twith Exponential Function

Abstract

This paper is concerned with a new method that identifies the equivalent circuit constant of synchronous machines using D. C. decaying current. The procedure is as follows;
(1) D. C. voltage is applied to the armature winding (two terminals with the third one open) of a stationary synchronous machine through a resistance. When two terminals are closed, the winding is short-circuited and the current in the armature winding decays. The whole process of current decay is recorded.
(2) The current decay is approximated by the exponential function, and values of the index number and coefficient are identified with the least square method.
(3) The equivalent circuit constant is identified from the relationship which is formed between these constants and the exponential function.
The starting performance of synchronous motor with damper winding is calculated using the method and agrees with actual data.
The test capacity is needed about 0.1% of a starting capacity with 50% voltage.