Optimal commutation in average torque control of switched reluctance motors

The problem of choosing the firing angles within two average torque control schemes for switched reluctance motors, based on 'current control' and 'voltage control', respectively is examined. The primary goal is the maximisation of the energy conversion per stroke. Secondary goals of maximising efficiency (within current control) and obtaining approximately flat-topped current waveforms (within voltage control) are also considered. The main contribution is the development of a general theory of the optimal turn-off angle. When the theory is applied to a simple machine model. It leads to simple and explicit formulae for the optimal turn-off angle in the voltage and current control schemes. The model requires minimal machine data and the computational requirements are very modest. Comparison with experiment shows an accuracy that is believed to be more than adequate for practical purposes: greater accuracy would require an exhaustive search. It is believed that the method will be a valuable aid for the SR motor engineer in the field, and allow easier programming of variable-speed switched reluctance motor drives in the future.