Analysis of average torque in switched reluctance motor with unipolar and bipolar excitations based on an improved Fourier series model

Switched reluctance machines (SRMs) are usually excited by unipolar current by employing asymmetric bridge inverters. It is also possible to excite SRMs by bipolar current using a three-phase bridge inverter. The main objective of this paper is to derive general analytical expression of average torque in SRMs under both unipolar and bipolar excitations, and to analyze their average torque under three working bipolar excitation patterns, with reference to unipolar excitation. All analyses are verified by the finite element analysis and measurements on a prototype 6/4 SRM.