Recent technical trends in variable flux motors

This paper reviews recent technical trends in variable flux motors. Permanent magnet motor is a major component to realize high torque density with keeping high efficiency. However, when high speed revolution is required for further miniaturization, as well as the large torque in the low speed region, the flux yielded by the permanent magnet encounters a serious trade-off, i.e. the former needs less flux and the latter requires much. The solution for this trade-off is varying the flux. In general, the flux of the permanent magnet is constant, and many efforts are under development to overcome this as to be shown in this paper.