A Hybrid-Excitation Synchronous Motor with a Change in Polarity

The hybrid-excitation permanent magnet (HEPM) motor is a synchronous motor characterized by a rotor that includes both permanent magnets and excitation windings. Thus, an active change in the magnetic flux by means of the excitation current is possible. In particular, the hybrid-excited rotor studied in this paper can be used to change the number of poles of the rotor itself. At the same time, the stator winding is also designed to perform a polarity change. The change in polarity allows users to obtain different torque versus speed characteristics with the same motor. In particular, a configuration with a lower pole number exhibits low torque at high speeds, while a configuration with a higher pole number produces high torque at low speeds. In this way, a single HEPM motor behaves like two different machines, extending the usual operating speed range of synchronous motors. In this paper, an HEPM rotor configuration is designed, and its performance is analyzed through finite element electromagnetic and thermal simulations.