Design of a switched reluctance machine assisted by DC field windings for a turbo blower

A switched reluctance machine (SRM) is applicable to high speed applications due to its simple magnetic structure and mechanical robustness. During the operation of a converter, however, it causes high peak phase current which leads to a rise in the VA rating of an SRM system. Therefore, this paper investigates the reduction of peak phase current and describes the basic design procedure of an SRM along with a converter topology of the machine assisted by DC field windings. Physical dimensions are first determined, and then the field windings are employed in the SRM without changing copper area and copper weight. Also, a commutation method is investigated by activating the field windings matching with switching angles in phase windings in order to achieve both low peak current and high efficiency at the same time. By doing so, the dynamic performance of an SRM assisted by DC field windings is estimated and compared to conventional symmetric and asymmetric winding configurations. It is concluded that the criterion of peak current reduction and efficiency improvement is met by matching the turn-off angle of field windings based on that of phase windings.