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 'vo ltage control'. respectively, is examined. The primary goal is the maximisa tion of the energy conversion per stroke. Secondary goals of maximising eff iciency (within current control) and obtaining approximately flat-topped cu rrent waveforms (within voltage control) are also considered. The main cont ribution is the development of a general theory of the optimal turn-off ang le. When the theory is applied to a simple machine model, it leads to simpl e and explicit formulae for the optimal turn-off angle in the voltage and c urrent control schemes. The model requires minimal machine data and the com putational requirements are very modest. Comparison with experiment shows a n 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. a nd allow easier programming of variable-speed snitched reluctance motor dri ves in the future.