Stable Equilibrium Rotor Positions for Three-Phase Switched Reluctance Machine

Abstract

In mobile applications such as eletric vehicles, weight and installation space are the primary limiting factors that affect the system efficiency and consequently the driving range. Reusing the machine windings of an electrical machine as inductors, e.g. in DC-DC converters for onboard chargers, saves weight and space. However, currents in the machine windings when operating as DC-DC converter can result in undesired torque ripple generated by the machine. Therefore, stable rotor positions of a switched reluctance machine have to be found to prevent it from rotating in DC-DC converter operation mode. In this study, stable rotor positions for a wide range of current distributions are determined, enabling flexibility in the choice of currents. A method to analyze such stable equilibrium positions for switched reluctance motors is presented. The proposed method is used to determine the stable positions that facilitate flexible current distribution between phases. Moreover, locus curves are calculated, simulated, and measured to illustrate and evaluate stable rotor positions for the various current distributions.