Commutation Angle Maps Evaluation for Magnet Arrangements of Interior Permanent Magnet Synchronous Machines in Electric Vehicles

Abstract

The commutation angle, γ , of an interior permanent magnet synchronous motor's (IPMSM) vector diagram, plays an important role in compensating the back electromotive force; both under load phase current variations and/or when an extended speed range, being near the constant power range, is required by the application. This commutation angle is defined as the angle between the fundamental of the phase current and the fundamental of the back-emf. It can be utilized to provide a compensating effect in IPMSMs. This is due to the reluctance torque component being dependent on the phase current before the extended speed range. A real-time maximum torque per current and voltage strategy is employed to find the trajectory and optimum commutation angles, γ , where the level of accuracy depends on the application and available computational speed. A magnet volume reduction is proposed in this paper to minimize the permanent magnet mass to motor torque density, whilst maintaining the phase current below its maximum rated value. A mapping of γ allows the determination of the optimum angles as shown in this paper. The 3rd generation Toyota Prius IPMSM is considered the reference motor, where only the rotor configuration is altered to allow for an individual assessment. The electric vehicle's performance during acceleration and deceleration using various IPMSM rotor configurations is evaluated for a given four-wheel-drive vehicle. The powertrain uses two single-gear onboard, under standard drive cycles.