Abstract: Due to the removal of the slotted structure, the winding of the slotless permanent magnet synchronous motor (PMSM) is directly exposed to the high speed alternating air gap magnetic field, and a large amount of eddy current loss is induced inside. For the slotless PMSM, the winding eddy current loss is one of the important sources of the total loss of the slotless PMSM, and the analysis and calculation of the winding eddy current loss is very important. However, the analysis and calculation methods of winding eddy current loss proposed at present are all based on the straight conductor winding, and the calculation principle is based on the shape and distribution of the eddy current loop in the straight conductor. However, the hexagonal winding contains both the straight conductor and the inclined conductor, and the eddy current distribution is different from the straight winding. The traditional calculation method of the eddy current loss of the straight winding is no longer applicable to the hexagonal winding. Therefore, this paper studies the distribution shape and distribution law of eddy current in hexagonal conductor. Based on the hexagonal winding structure flexible printed circuit board (FPCB) winding structure, a three dimensional semi analytical calculation model of eddy current loss of hexagonal FPCB winding structure is proposed. The correctness and effectiveness of the proposed three dimensional semi analytical calculation method for eddy current loss of hexagonal winding are verified by three dimensional finite element calculation and prototype test.

Key words: slotless motor, end magnetic flux leakage, eddy current,  , winding , loss