Torque ripple and copper loss minimization for a family of mutually coupled switched reluctance machines

In this paper, an optimal torque sharing function (TSF) for a family of mutually coupled switched reluctances machines (MCSRMs) is proposed to minimize the torque ripples and copper losses over the wide speed range. Winding distributions and torque production mechanism of a family of mutually coupled switched reluctance machines including short pitched, full-pitched, and fractionally-pitched MCSRMs are discussed. Then an optimal TSF for the MCSRM is obtained by solving the optimization problem. The objective of the optimal TSF combines the squares of three-phase currents (copper loss); the torque equation for the MCSRM in the linear magnetic region is expressed in terms of both self-inductance and mutual inductance, which is used as the equality constraint of the optimal TSF; the limits of the rate of change of current references serve as the first inequality constraints, while three-phase current limits serve as the second inequality constraints. Simulation results show that in the linear magnetic region, the torque ripples of the MCSRM using the proposed optimal TSF are only one half and one fourth of those produced by conventional sinusoidal and square current excitations over the wide speed range while keeping the power losses minimum.