Design of a Variable-Flux Permanent Magnet Machine using Alnico 9 and Comparison with a Baseline Interior Permanent Magnet Machine

This paper provides details of the design and analysis of a variable-flux (VF) permanent magnet machine using Alnico 9 magnets for electrified vehicle applications. Temperature-dependent demagnetization and repeating demagnetization of Alnico 9 magnets are experimentally tested. Torque density of the VF machine is optimized using finite element (FE) method. The mechanical capability of the VF machine is verified with Multiphysics Simulations. It is found that, in some operating areas, the designed VF machine has a slightly better efficiency and power factor compared with a baseline interior permanent magnet (IPM) machine. The torque-speed capability and the power density of the VF machine still cannot compete with those of the baseline IPM machine. This work addresses the challenges of designing a high torque density VF machine with rare-earth-free magnets and explore the potential of applying VF machine in electrical vehicle applications.