Split Ratio Optimization of Short-Time Duty PM Brushless DC Motors Considering Stator Winding Local Thermal Limitations

High-power-density short-time duty permanent magnet brushless DC motors (PM-BLDCM) has a large temperature gradient. There is a risk of insulation damage due to overheating of stator winding. Due to some application requirements, the dimensions, speed and torque of the motor are fixed. The split ratio and the maximum flux density of stator lamination (B
_m
), which are highly relevant to loss and temperature rise rate, are optimized to minimize the stator temperature. The current density limitation is considered in the optimization to avoid local overheating of stator winding. The analytical optimal combination of split ratio and B
_m
is obtained by the deduction of the expression of stator temperature and current density. The errors between analytical results and finite element analysis results are less than 8%, which proves that the optimization method can effectively limit the winding temperature.