Analytical Estimation of Eddy Current Losses in PCB Winding for the Optimal Sizing of PM Slotless Motor

This paper aims at evaluating the eddy current losses during the optimal sizing of slotless BLDC motors in the particular case of winding printed on a flexible PCB. Although this kind of winding can significantly improve the performance of the machine, it is necessary to properly consider the effect of eddy current during the design, especially at high speed. With printed winding, large areas of conducting material are exposed to a perpendicular time varying magnetic flux, which favors the formation of eddy currents. Therefore, this paper presents analytical developments to estimate the losses due to these currents, considering complex winding geometry. Furthermore, using analytical electric and magnetic models, full motor optimizations are performed and compared to optimizations using finite element models instead. Finally, a study about the impact of the nominal speed on the optimal design of the slotless motor is proposed.