Optimization Design of Bearingless Synchronous Reluctance Motor

In order to overcome common drawbacks of the low torque density and power factor for conventional bearingless synchronous reluctance motors (BSynRMs), a novel BSynRM rotor structure with ferrite magnets is designed in this paper. First, the basic structure and operation principle of the BSynRM are introduced, and the mathematical models of torque and suspension forces are deduced. Second, based on the finite element analysis method, the parameters of flux barriers layer, rotor rib width, and permanent magnets are optimized to increase the salient pole ratio and the difference between d and q axes inductance. Third, the performance of torque, suspension forces, and power factor for the optimized motor is compared with that of the traditional BSynRM. The research results show that the torque density and power factor increase about 54.4% and 56.3% respectively at optimal angle, whereas the average suspension force decreases about 15.7% owing to magnetic saturation. The optimized motor is validated to have good suspension and speed regulation performance.