Permanent-Magnet Synchronous Motor (PMSM)
A permanent-magnet synchronous motor (PMSM) is an AC motor whose rotor carries permanent magnets and turns in step with the stator's rotating magnetic field.
What it means in an EV
In an EV traction drive, the inverter controls current in the stator windings. The magnetic field created by those windings rotates, and the rotor's magnet field follows it at synchronous speed. An induction motor differs because its rotor operates with slip relative to the stator field.
PMSM is not a synonym for every permanent-magnet motor. The term identifies synchronous AC operation; PMSM designs can use surface or interior magnets and may combine magnet torque with reluctance torque. A Wound-Rotor Synchronous Motors is also synchronous, but creates its rotor field with electrically excited windings rather than permanent magnets.
These distinctions affect materials, losses, control and packaging, but the acronym alone does not establish the efficiency or performance of a complete drive unit. For the detailed construction and operating trade-offs, see Permanent-Magnet Synchronous Motors.