Circulating currents of delta connected fractional slot machines for mass production

Abstract

Circulating currents are a major issue in permanent magnet BLDC electric motors with delta connected windings. In 3-phase machinery they are driven by harmonics whose order is equal to a multiple of the number of phases. The harmonics occur because of special slot/pole combinations, rotor and stator asymmetries, phase imbalances and magnetic saturation inside the teeth and the yoke. In this publication all of these aspects are investigated. The advantages of delta compared to wye connection are also pointed out in terms of mass production. External sources of circulating currents like inverter operation are not part of this publication.