Improvement of characteristics by flux barrier shape and magnet thickness of IPMSM with Dy-free rare-earth magnet

Interior permanent magnet synchronous motors (IPMSMs) that employ rare-earth permanent magnets (PMs) containing dysprosium (Dy) are used in home appliances, electric vehicles and hybrid electric vehicles. However, it is desirable to reduce the amount of Dy used in such PMs due to its high cost. This study investigates the rotor structure of an IPMSM with a Dy-free rare-earth PM. Flux barrier shapes and PM thicknesses that enhance the irreversible demagnetization are investigated. In addition, a rotor structure that improves the irreversible demagnetization is proposed. We demonstrate that the proposed rotor structure without Dy improves the irreversible demagnetization without degrading the motor performance.