Characterization of switched reluctance machines using Fourier series approach

This paper presents a new method for the analytical representation of the phase inductance of a switched reluctance machine (SRM), as a function of position and current, taking into account the nonlinearity of the magnetic circuit. It is based on Fourier series expansion with step-by-step current dependent adjustable coefficients. Analytical expressions for the calculation of instantaneous phase inductance, flux linkage, coenergy and electromagnetic torque as functions of rotor position and winding currents are derived. To evaluate the accuracy of the proposed approach, the current-position dependent inductance profile and static torque curves are compared to experimentally correlated finite element analysis results, of two prototype switched reluctance motors: a rotating and a linear motor. The outcome is a mathematically elegant technique, able to characterize a given machine with a very good degree of accuracy, as confirmed by the compared results.