Experimental Comparison of Synchronous Reluctance Motors with and without Ferrite Magnet Assistance

Both, the synchronous reluctance motor (SynRM) and the permanent magnet assisted synchronous reluctance motor (PMaSynRM), are high-efficient inverter-fed motors in variable-speed drive applications. Here, both machines are designed for the same stator of an 11 kW totally-enclosed, fan-cooled standard cage induction motor. The experimental comparison between both motors confirms that the PMaSynRM using ferrite magnets has a 20% higher nominal output torque for the same rated current, an increased power factor of 0.88 instead of 0.81 and a higher efficiency by 1.2%-points in the base speed range at 1500 rpm as well as a 27% higher steady-state output power in the field-weakening range at 3000 rpm. On the contrary, the performance of the PMaSynRM decreases with increasing ferrite magnet temperature. Further, the ferrite magnets demagnetize partially at a three-phase sudden short-circuit.