Evaluation of IPMSMs with concentrated windings using powder magnets for high torque

Motors that use rare-earth permanent magnets typically exhibit high performance and are widely used in industry. However, rare-earth permanent magnets are expensive, and there is concern about the stable supply of rare-earth materials. On the other hand, there are methods by which distributed and concentrated windings can be used in the stators of IPMSMs in order to reduce the size and cost of motors. In the present study, IPMSMs with concentrated windings using powder magnets that have a higher coercive force than ferrite magnets are examined and are discussed with respect to rotor structure in order to obtain high torque. When sintered magnets are used to replace powder magnets in the same rotor structure, the maximum torque decreases by 25%. The three-layer circular arc structure has the highest torque (85% of the structure using sintered magnets). Moreover, two basic structures using sintered and powder magnets and the three-layer circular arc structure are compared with respect to torque and output power characteristics. The maximum torque of the basic structure using powder magnets and the three-layer circular arc magnet structure are 75% and 85%, respectively, of that of the basic structure using sintered magnets. The output power of the basic structure using powder magnets and the three-layer circular arc magnet structure in the high-speed region are 64% and 84%, respectively, of that of the basic structure using sintered magnets. The maximum torque and the output power of the three-layer circular arc magnet structure was substantially improved.