Pole-Changing in Synchronous Machines: A Reluctance-Permanent Magnet Hybrid Motor

The change of the number of poles in three-phase electrical machines has always been applied exclusively to induction motors. The main advantage of varying the number of poles in induction motors is the possibility to operate with two different synchronous speeds. This article investigates the possibility to vary the number of poles in synchronous motors as well. A hybrid reluctance-permanent magnets synchronous motor is presented. Its design is described, then the operating principle is illustrated through finite element analysis. Finally, the dual polarity operation for such a synchronous motor is demonstrated through experimental tests on a prototype. The work shows that a dual-polarity synchronous machine can be designed and its operation and capabilities are verified through the prototype characterization.