ESTIMATION OF SWITCHED RELUCTANCE MOTOR LOSSES

This paper describes a method of predicting switched reluctance motor (SRM) losses under the operating conditions inclusive of saturation. General expressions for the flux frequencies in different parts of the core are derived. Fourier analysis is applied to decompose the flux waveforms into their constituent sinusoidal components, which are then used in conjunction with the loss characteristics of the core material to estimate the corresponding loss components. The dependence of these losses on the magnitude and waveform of the excitation current, the switching frequency, and the conduction period per phase is investigated for a peaky and a flat-topped current waveform. It is shown that the core flux contains significant proportions of both even and odd harmonics, particularly in the stator and rotor poles. The maximum losses are shown to occur in the stator core. Further, it is established that SRM core losses are proportional to the excitation mmf and not the applied voltage, particularly under saturation. Mathematical expressions for predicting copper losses are also described. Experimental verification on a 6/4 pole laboratory prototype is presented and discussed. The measurement technique applied and some of the problems encountered in the course of the study are discussed.