Dynamic modeling of nonlinear SRM drive with Pspice

In this paper, a comprehensive nonlinear dynamic model for a switched reluctance motor (SRM) drive using Pspice is presented. The SRM is represented by its nonlinear dynamic equations and the magnetic model of SRM includes the representation of inductance-current-position characteristics which closely match those obtained experimentally. The variation of the phase inductance with rotor position is expressed by a limited number of Fourier series terms. The coefficients of the Fourier series are determined by the values of the inductance at the aligned position, unaligned position and a position midway between the two. The nonlinear relationship between the phase inductance and the current is represented by polynomial functions whose coefficients are derived by static characteristics obtained from finite element analysis or experimental results. Since Pspice is a circuit oriented package, any type of converter and control scheme can be modeled with ease and hence the component ratings can be selected based on simulation results. Further, any type of converter/motor faults as well as phase asymmetries can also be simulated. It is also possible to simulate various control strategies for low and higher speed operations and obtain optimum control angles. The details of the developed model and the simulation results obtained for a 300 W, 12 V, 8/6 SRM drive in various operating regions are presented in this paper. To validate the model, the simulation results are compared with experimental and finite element analysis results.