A study of the effects of machine winding space harmonics and advanced phase current switching on torque and performance quality in brushless DC motors using PSpice modeling

The effects of space harmonics arising from the topological geometries of the magnetic circuits and winding layouts of permanent magnet brushless dc motors (BDCMs) on their performance are studied here. This includes the synergisms between the space harmonies and the time harmonics generated by the BDCM controller switching. This was accomplished through the development of a PSpice-based model that is presented here. This model fully includes the impact of the space harmonics through the profile variations of all the motor winding's self and mutual inductances with the rotor angular position. These inductances are introduced to the model in a Fourier series form. The simulations, which include all the controller (drive) circuit electronic switching effects reveal the impact of these time and space harmonic synergisms on time-domain motor torque profiles, torque-speed characteristics, line-to-line voltage waveforms, current waveforms, and other performance aspects of the motor and drive. Comparison between simulations, with and without the effects of space harmonics, and test results are presented. In the paper, two 1.2-hp and 15-hp case studies of BDCMs are investigated.