Harmonic Analysis of a BLDC Motor Under Demagnetization Fault Conditions

The continuous operation of a Permanent Magnet (PM) Brushless DC (BLDC) motor in industrial applications get subjected to unfavorable environmental conditions. This includes physical and thermal stresses leading to the emergence of fault. Faults on the rotor side is generally inflicted by the change in magnetic coercivity (HC) leading to the demagnetization of a PM in the machine. The effect of demagnetization brings a significant change in the motor characteristics performance including phase currents and motor back-EMF. This paper shall therefore, elaborate on the effect of demagnetization fault on the harmonics of current and back-EMF of the BLDC motor. The demagnetization faults taken in our study are uniform and extreme demagnetization effects. On the occurrence of these two faults the change in THD and percentage share of harmonics are being analyzed in order to draw an inference for the detection and classification of demagnetization faults in the motor. The outcomes obtained are further compared with the motor characteristics under healthy operation to have distinct identification to fault.