Modeling and Analysis of Demagnetization Faults in BLDC Motor using Hybrid Analytical-Numerical Approach

Abstract

Brushless Direct Current (BLDC) motors are the type of Permanent Magnet Synchronous Motors (PMSMs) with trapezoidal back-EMF. These motors are driven using Voltage Source Inverter (VSI), by appropriate switching through semiconductor devices. Different models of a typical BLDC motor have been reported in the literature. Models could be of different types such as analytical model where several assumptions are taken in order to simplify the analysis. While the Numerical Methods (NMs) approach such as Finite Element Method Magnetics (FEMM) gives more accurate solutions. This paper aims to combine both these approaches to develop a Hybrid MATLAB/ Simulink™ -FEMM model for a closed loop BLDC motor drive using a Hysteresis Current Control (HCC) technique. The developed model is simulated both under healthy and faulty conditions. In order to simulate the effect of demagnetization faults in the machine, demagnetization is introduced in the PM through various methods like change in magnetic coercivity which shall account for the uniform demagnetization of a pole and secondly, placement of broken Permanent Magnets (PMs) in the rotor to induce magnet defect in the machine. The performance of the motor through change in quantities like stator current, back-EMF, electromagnetic torque and mechanical speed are analyzed in detail to have a comparative study of the BLDC motor performance both under healthy and demagnetization fault conditions. Detailed simulation results have been discussed for each type of demagnetization faults.