Retrofitting of a Chevy-Bolt IPM Motor with a PM-Assisted Synchronous Reluctance Rotor Enabled with a Blend of Heavy-Rare-Earth-Free Neodymium and Ferrite Magnets

In this paper, the rotor of an existing Chevy-Bolt Interior Permanent Magnet (IPM) motor, consisting of rare-earth permanent magnet based rotor, is replaced and retrofitted with a PM-Assisted Synchronous Reluctance Machine (PMASynRM) rotor enabled with a combination of Heavy-Rare-Earth (Dy-free) Neodymium and Ferrite magnets. For this, a multi-objective design optimization of the PMASynRM rotor, aimed at minimizing rare-earth magnet volume and permanent demagnetization risk of magnets, while achieving performance comparable to the Chevy-Bolt motor across its operating speed range, is performed. This is followed by mechanical stress optimization of rotor lamination at maximum speed, to ensure its structural integrity. The optimized rotor design, having 26% rare-earth magnet volume, is manufactured and retrofitted into a Chevy-Bolt motor. A preliminary set of test results is presented and found to be consistent with the Finite Element Analysis (FEA) based simulation results.