Design considerations and test results for a doubly salient PM motor with flux control

A prototype of a new permanent magnet machine is presented in this paper, and its experimental tests fully documented. The motor incorporates the benefits of PM machines, namely the high power density and efficiency, overcoming some of its major disadvantages, such as high cost and limited speed range. Low cost is achieved due to the utilization of simple ceramic PM (ferrite) magnets but the unique flux concentrating magnetic structure allows for the maintenance of a high air gap flux density and consequently high power density. All the active material (coils and magnets) are placed in the stator, so that the rotor structure is very simple like that of the switched reluctance machine (SRM). An extended speed range is obtained thanks to a field coil that can be used to weaken the PM field at high speed or to boost the field at low speed.