Robust Design Process to Restrain Irreversible Demagnetization of Interior Permanent Magnet Synchronous Motor Applied in Railway Vehicles Using Dysprosium-Free Permanent Magnet

Trends of traction motor of railway vehicles have been shifted from induction motors to permanent magnet motors. Recently, studies have been conducted on dysprosium-free permanent magnets. Dysprosium is a heavy rare earth element that has a great impact on performance of motors. However, dysprosium affects the coercive force of a permanent magnet and can produce irreversible demagnetization. Conventional studies have focused on improving the performance of motors using permanent magnets without heavy rare earth elements. In this study, a robust rotor design process includes the way to restrain irreversible demagnetization using a dysprosium-free permanent magnet. First, the irreversible magnetization of bar-type and V-type magnets, which are basic models of interior permanent magnet synchronous motors, is analyzed. Next, expected demagnetized parts of the main magnets are used as a submagnets, which make magnetic field bypass both sides of the submagnets, and magnets are added in submagnets regions to compensate gap of performance between target model and double type models. Finally, parameter analysis is performed on the design variables of the main magnet. The proposed the robust design process to restrict irreversible demagnetization proves its validity through finite element analysis.