Optimized Design of a Brushless DC Permanent Magnet Motor for Propulsion of an Ultra Light Aircraft

The paper presents an optimized design of a low mass brushless DC (BLDC) permanent magnet motor for propulsion of an ultra light aircraft. The optimization has been carried out using Differential Evolution algorithm implemented in Mat lab combined with SPEED and MotorCAD software packages for electromagnetic and thermal modeling of the BLDC motor using ActiveX technology. The credibility of the models created with SPEED and MotorCAD has been confirmed by comparing the results of simulation and measurement performed on a 12 kW synchronous permanent magnet motor available in the laboratory. The goal of the optimization has been to minimize the weight of the motor under condition that the motor delivers rated power of 15 kW at rated speed of 3000 rpm with hot-spot temperature not exceeding the temperature limits of class F insulation (155 degrees C). Two optimal BLDC motor designs with slot/pole combinations 12/10 and 18/16 have been obtained. The motor with 18 slots and 16 poles yields the highest torque density with the lowest mass of active parts (copper+laminations+magnets) of only 5.1 kg.