Irreversible Demagnetization Analysis with Respect to Winding Connection and Current Ripple in Brushless DC Motor

In this study, a characteristic analysis of irreversible demagnetization in brushless dc motors (BLDCMs) according to the winding connection type, wye, and delta, is conducted. Depending on the excitation sequence and inverter output current for each winding method, different irreversible demagnetization characteristics are caused under the equal-input-limit condition. However, in contrast with the ideal current waveform, the current ripple inevitably occurs when pulse width modulation (PWM) control is applied. In the case of a large current ripple, the irreversible demagnetization characteristics could deteriorate due to the instantaneous increase in the synthesized magnetomotive force. Therefore, with regard to the switching frequency, we analyze the irreversible demagnetization characteristics of the delta and wye connections for BLDCM with PWM control. The validity of the results is verified through finite element analysis.