Design optimization of turn-off snubber for switched reluctance drives

The design optimization of industrial motor drives with restricted regard to a nominal operating point has never satisfied engineering concerns over optimal drive performance at other operating points. This is especially the case, where the drive operation is not concentrated on a few operating points. Therefore, drives as well as drive components, such as machine, electronic converter and control system, have to be designed to present an optimal performance at all considered operating points. This paper describes a design optimization methodology for turn-off snubber circuits used in switched reluctance (SR) drives. The goal of the optimization process is to minimize the switching losses of the electronic converter at all operating points corresponding to an enclosed region in the torque-speed plane. The paper shows the better converter efficiency in the presence of the optimal turn-off snubber. Moreover, a converter loss evaluation procedure is proposed. The accuracy of this procedure is verified by comparison of the predicted results with those obtained from the Simplorer package and experiments. Because separately measuring of the converter switching losses for a running drive is not practical, the effectiveness of the design optimization methodology is then investigated based on the proposed loss evaluation procedure.