Control of the Synchronous PM Motor

Permanent magnet machines have become prevalent among very high-speed machines and, to the author’s knowledge, no machine other than permanent magnet has been reported to operate beyond the speed of 130.000 rpm. So-called PM synchronous machines (PMSM) with sinusoidal phase currents are generally preferred when low loss and smooth torque are important [1]. On the other hand, using high-frequency sinusoidal currents in the stator makes the design of a power converter more difficult and also complicates the implementation of control algorithm given a short switching period. A control method for PMSM must ensure stable, synchronous operation of the machine at high speeds having, at the same time, computational complexity tolerable by the given microcontroller. Since small high-speed machines, as a rule, lack space for a position/speed sensor, sensorless operation is usually required.