Comparison analysis of demagnetization and torque ripple in accordance with freewheeling current in BLDC motor

Demagnetization and commutation torque ripple are affected by freewheeling current (FC) when inverter switch turns on or off. Recently, many studies on commutation torque ripple considering the FM are actively conducted for high efficiency. However, the studies on the demagnetization considering the FM are not actively conducted. So, we conducted demagnetization analysis depending on the variation of (FC) for improving the reliability of brushless dc (BLDC) motor. If fault of BLDC motor is occurred such as inter-turn fault owing to broken coil insulation, the input current increases and is destroyed by the electrical and magnetic imbalance. For this reason, the inter-turn fault generates demagnetization. If demagnetization phenomenon is occurred, magnetic flux is reduced by decrease of back electromotive force, and then electric loading is beyond magnetic loading by increase of input-current. So, we need to analyze the demagnetization phenomenon.