A permanent-magnet motor is a motor with
poles made up of permanent magnets.
Even though most permanent-magnet
machines are used as DC machines, they are
occasionally built as synchronous machines
with the rotating field winding replaced by a
permanent magnet.
The permanent-magnet AC motor operation
resembles that of the permanent-magnet
stepper motor. Just as the stepper motor, the
excitation frequency determines the motor
speed, and the angular position between the Image from www.ewh.ieee.org
rotor magnetic axis and a particular phase when it is energized affects the
developed torque.
Often, permanent-magnet (AC) motors are called brushless motors