Torque Ripple Calculation of the Two-phase Permanent Magnet Synchronous Motor Supplied by a Triac Converter

A synchronous motor with ferrite permanent magnet rotor is a good solution forsmall pump applications. It also has some drawbacks. The most important of them seems tobe its inability to start directly on the mains, Permanent magnet motor has to by equippedwith an electronic circuit for direct starting, which increases motor price. Anotherdrawback is the torque ripple for the non-harmonic supply. This paper shows analyticalcalculation of the torque ripple of the small permanent magnet motor, which does a triacconverter supply. The converter forms two-phase supply voltage of 25 Hz frequency, fromone-phase 50Hz mains.