Enhanced Efficiency Inverter with Winding Changeover Circuit for Ultra High-Speed SPMSMs in Fuel-Cell Electric Vehicles

Ultra-high-speed motors typically have reduced efficiency at low speeds due to their design for wide-range operation. To address this issue, this study proposes a novel motor drive system that integrates a TRIAC-based changeover circuit and a silicon carbide (SiC) -based inverter. The proposed changeover circuit adjusts the motor's circuit, enabling the stator winding to switch between series and parallel modes. At low speeds, the motor operates in series mode to reduce stator current, while switching to parallel mode at high speeds to maintain optimal performance. This approach effectively improves motor efficiency, particularly at low speeds. Additionally, a zero current switching method prevents current spikes during switching during mode transitions. The proposed method was experimentally validated using surface mounted permanent magnet synchronous motor (SPMSM) and the results demonstrate the system's stability and improved efficiency.