Non-linear Magnetic Characteristics Modeling for Switched Reluctance Machines

This paper presents a simple mathematical model for the non-linear magnetic characteristics of a switched reluctance machine (SRM). The proposed model realizes the flux-linkage characteristics by representing the flux-linkage as a unique non-linear function of the excitation current and its coefficients vary with the rotor position. This proposed model is based on a rational function with first-order and second order polynomials in the numerator and denominator, respectively. Initially, for simplicity, it is considered that the coefficient of the numerator is equal to the air-gap inductance. Then, the coefficients of denominator is obtained using the nonlinear regression to fit inductance and excitation current profile under saturation. For validation, these characteristics, obtained from the proposed model and standard finite element method using Ansys Maxwell, are compared along with the current waveforms to confirm the accuracy of the proposed model. Finally, a sensor-less scheme is implemented, where the turn-off angle is estimated using the proposed model, and results are presented for further validation of the proposed model.