Efficiency optimization Method of an Ultra-high Speed, Low Torque Permanent Magnet Motor with Multiphase Configuration

In this paper, design and efficiency optimization of a five-phase permanent motor has been done with rated speed of 500,000 rpm and power of 100 watt. With compact design and high power density, ultra-high speed motors can be a potential candidate for automotive applications. However, one of the major issues for ultra-high speed motor performance is higher losses due to the high excitation frequency. Higher losses can degrade overall system performance and increase the temperature of the motor which can lead to magnet demagnetization. Multiphase winding configuration where per phase current is lower than three phase structure can be a feasible solution to increase the efficiency coupled with optimization method concerning design parameters. In this study, design parameters of the motor such as magnet and stator outer length has been selected for efficiency optimization of the motor. Along with the efficiency, weight and current rating of the motor have been considered as constraints. After that, by using multivariate nonlinear regression analysis and fmincon optimization, optimized magnet and stator length of the motor has been calculated. Performances of optimized motor has been compared with those of a benchmark motor and analyzed for performance improvement.