Demagnetization and Thermal Analysis of Six-Phase Permanent Magnet Motor-Based Integrated Onboard EV Charging

Integrated onboard battery charger (IOBC) is an emerging technology that charges electric car battery packs using the same circuitry for electric propulsion, reducing the cost and weight of an electric vehicle (EV). During charging, while ensuring zero-average torque to avoid rotation, permanent magnets (PMs) synchronous motors with fractional slot concentrated winding (FSCW) may be subjected to irreversible demagnetization due to sub and super space harmonics with relatively high magnitudes. This article presents the design and optimization of six-phase surface-mounted PM (SPM) and interior PM (IPM) motors with FSCW, considering the impact of PM demagnetization during IOBC. A detailed thermal and demagnetization analysis is conducted to identify the risk of PM demagnetization during propulsion and IOBC modes. The performance and demagnetization risk for SPM and IPM motors with different power ratings used in commercial EVs are compared at various operating conditions. In the integrated charging process, grid-to-vehicle (G2V) and vehicle-to-grid (V2G) power circulations are practically implemented. Simulations are conducted using a 3-D finite element analysis. Experimental results of a 15 kW IPM motor are provided for further verification.