Optimal design of winding back EMFs in doubly salient permanent magnet motor

Winding back EMF is an important parameter in doubly salient permanent magnet (DSPM) motor, and optimal design of winding back EMF aids in the performance improvement of DSPM motor drive. For a drive system which is composed of 12/8-pole flume-rotor DSPM motor and single-chop controlled three-phase inverter, the influence of winding back EMF on torque output capacity is first discussed. Then, the influences of winding back EMF on working modes, power loss distribution of the inverter, and system loss are detailed, with some important conclusions drawn. Based on the above analysis, the optimal design rule for winding back EMFs is deduced. With the optimal design rule, a design practice of winding back EMF is given for a 9 kW, 12/8-pole DSPM motor in an aero application. Experimental results before and after optimum design of winding back EMFs show that the design according to the proposed optimal design rule improves overall efficiency, makes power loss evenly distributed in the inverter, and enhances system performance.