A survey of mechanical and electromagnetic design techniques for permanent-magnet motor flux-weakening enhancement

Permanent-magnet synchronous motors are widely used in vehicular traction applications due to their high efficiency and torque density. A critical point of their operation is the flux weakening needed at high speed, which usually implies injecting a d-axis demagnetizing current by the inverter. This paper presents a critical survey of the alternative approaches found in the literature and patent databases to enhance flux-weakening performance by acting on motor mechanical and electromagnetic design.