Thermal Analysis of Stator Iron-Core-Less PMBLDC Motors Considering Both Winding Eddy and Circulating Current Losses

Thermal analysis of three stator iron-core-less PMBLDC motors considering winding eddy and circulating current losses is investigated. First, the effects of strand diameter, permanent magnet (PM) magnetization and rotating speed on the above mentioned two winding losses and thermal characteristics are investigated by 3D finite element method (FEM). It is found that both strand diameter and rotating speed have great impacts on the temperature rise, parallel and radial magnetizations have almost identical temperature rise results. Then, influence of eddy and circulating current losses on the thermal characteristics of the three PMBLDC motors are further studied, separately. Furtherly, comprehensive study of the two winding losses on the thermal characteristics is carried out. Results show that thermal analysis considering both winding eddy and circulating current losses in parallel thin strands is vital during motor primary design process considering the limited insulation level of wires and PMs. Finally, three prototypes with different combinations of strand diameters and parallel numbers are selected for the calculation of eddy current losses and temperature rise experiment. Experimental results demonstrate the effectiveness of the developed 3D FEM models and validate the obtained simulation results. This paper clarifies the key influence factors, i.e., windings of different wire diameters, PM magnetization and rotation speed, on temperature rise characteristics of such iron-core-less motors, which provides guidance for the subsequent design of such three types of motors.