An Identification of Equivalent Circuit Constants of Synchronous Machine using Fourier Transformation with DC Decaying Current

Abstract

It is almost impossible to measure the starting performance of middle and large synchronous motors in a factory, because it needs a large capacity of equipments to test their performance. Authors propose a new method that identifies the equivalent circuit constants of synchronous machines to predict their performance.
The procedure is as follows; first, the DC decaying current in armature winding is measured and the frequency response by Fourier Transformation using the test data is calculated. Next, the square errors are minimized using the calculated operational impedance, and as a result the unknown constants in equivalent circuit are identified.
Moreover, we show the procedure to get true armature leakage reactance by inserting the external resistance between the field winding terminals.
The starting performance of a synchronous motor with damper winding (10kW-200 V-31.9 A-4P) is predicted by this method and agrees with actual data. The test capacity is about 0.1% to the installed capacity which is needed when the motor starts with 50% rated voltage.