Permanent magnet Synchronous motor and Commutator

摘要

A low-cost sine-wave drive for a 3-phase permanent magnet synchronous AC motor 20 (PMSM) in open-loop control is based on the measurements of two linear Hall sensors 16 positioned at a given electrical angle acting as an electronic commutator. The two hall sensors are excited by the sinusoidal flux distributions of magnetic ring with the same pole number as the PMSM rotor magnet, and the outputs of the Hall devices are normalised by a two-phase-type phase-locked-loop 222 in order to reduce the impact of the sensor mounting non-uniformity during mass production. Signals representing normalised orthogonal components of each sensor are ten used to control sinusoidal energising currents supplied to the motor. The peak torque and speed of the motor is simply controlled by adjusting the amplitude of pulse width modulation (PWM) carrier 26, and smooth torque control is achieved due to sinusoidal 3-phase currents.