An investigation into the torque behavior of a brushless DC motor drive

The authors use a previously developed model for the brushless DC motor (BDCM) to investigate its torque behavior. When the input currents and motor flux linkages are perfect, no torque pulsations are produced in this motor. However, imperfections in the current arise due to finite commutation times, while imperfections in the flux linkage can arise due to the phase spread, finite slot numbers and manufacturing tolerances. Using an harmonic analysis, the effects of these imperfections on the production of torque in a BDCM are investigated. It is shown that torque pulsations and a reduction in the average value of torque is produced, both of which can affect the performance of torque, speed, and position servos.<>