Investigation of additional AC losses in tooth-coil winding PMSM with high electrical frequency

Stator winding structure and its manufacturing in permanent magnet synchronous machines (PMSM) is the vital part of the whole machine design. It is important to follow particular procedures in order to keep the winding losses at the acceptable level, which include DC resistance loss and additional losses due to alternative magnetic flux within the area of the stator winding. The winding transposition or using of Litz wire, which is effective way of proximity loss suppression, sometimes cannot be implemented due to challenges in assembling or cost aspects (especially in low cost PMSM solutions). In this case it is important to know consequences of using straight (non-twisting) windings in PMSMs with relatively high electrical frequency. This article studies impact of the number of stator winding parallel strands on the additional AC losses distribution in the slot where this winding is located. Also, thermal condition (which impacts the life time of the insulation) of the winding is analyzed with different number of parallel strands. Current and temperature distributions in the slot conductors were attained by finite element method (FEM). The total losses caused by additional AC losses in the winding were compared with the measurements results.