Effect of air gap between PM segments on cogging torque and acoustic noise of BLDC motor

This research investigates numerically the characteristics of the cogging torque in a brushless DC (BLDC) motor caused by the air gap between permanent magnet (PM) segments, and proposes a design method to reduce the effect of the air gap between PM segments on the cogging torque and acoustic noise of a BLDC motor. A 3D finite element model is used to calculate the cogging torque while a microphone is used to measure the acoustic noise and overall sound pressure level of the BLDC motor.