The Internal Fault Analysis of Brushless DC Motors Based on the Winding Function Theory

This paper presents a new approach to analyze the stator inter-turn fault of a brushless dc motor. It is essential to analyze the behavior of the machine under internal faults and design appropriate protection systems to avoid expensive failures that might occur to the machine in the near future. The winding functions and inductance change of stator windings under internal faults are explained in detail, and the informative simulation results, based on the winding function theory, are provided to analyze a current´s abnormalities and torque pulsation under turn-to-turn faults. To verify the proposed analysis, the stator current, back-electromotive force, and resultant torque waveforms for both healthy and faulty machines are presented, utilizing both the finite-element method (FEM) and computer simulation based on dynamic equations. Finally, experimental results present the actual behavior under the stator faults. The detailed simulation and experimental results will be the guideline for early detection of internal failures in brushless dc motors.