A frequency response method to estimate inductance profile of switched reluctance motor

Inductance profile has an important bearing on the performance of a switched reluctance motor (SRM). This paper presents the results of a frequency response method to estimate the inductance profile of SRMs. The stator winding is energized by a variable voltage variable frequency supply. An approximate equivalent circuit incorporating stator resistance, winding inductance and loss component has been used to estimate the inductance at different rotor positions. The inductance value is obtained over a band of rotor positions spanning one rotor pole pitch. Supply frequency is varied from 10 Hz to 55 Hz. The method is found to be simpler to the one using DC switching and processing of transient response. Interestingly, inductance at any given rotor position is not found to be sensitive to excitation frequency. However, as could be expected, core loss under test condition is very sensitive to supply frequency. Typical test results on a 4 kW, 8/6 pole, 4 phase SRM are presented and discussed.