Torque Ripple and Unbalanced Magnetic Force of a BLDC Motor due to the Connecting Wire Between Slot Windings

In this research, the effect of the connecting wire between slot windings on the torque ripple and unbalanced magnetic force (UMF) of a brushless dc (BLDC) motor was investigated. A 2-dimensional finite element model of a BLDC motor that includes the effect of the connecting wires was also developed. It was found that the connecting wires generate pole harmonics in the torque ripple and UMF. Thus, a novel pattern of the connecting wire where all coils are located at rotationally symmetric positions is proposed in order to eliminate the pole harmonics of the torque ripple and UMF induced by the connecting wire. The experimental findings showed that the proposed pattern can effectively reduce the magnitude of the pole harmonics in the noise and vibration of a BLDC motor.