Synthesis of high performance PM motors with concentrated windings

Windings concentrated around the teeth offer obvious advantages for electric machines with radial air-gaps, because the volume of copper used in the end-windings can be reduced. The Joule losses are decreased and the efficiency is improved. These machines are still limited to applications of sub-fractional power and they generally present a reduced number of phases. In three-phase machines, the concentrated winding is too often restricted to a winding with a short pitch of 120 electric degrees, i.e. to a winding with performances reduced compared to the traditional structures. But there are a significant number of three-phase structures which can support a concentrated winding if the number of poles is increased. In this article, the author present a synthesis of the structures of three-phase machines with concentrated windings. In the first part, the structures with a regular distribution of the slots are presented. A systematic method is proposed to determine the windings and the performances are discussed. In the second part, the authors present original structures of three-phase machines with concentrated windings which use an irregular distribution of the slots. A specific method to identify these structures is described and a comparative analysis of the performances of the original and traditional structures is performed by using field calculation software