Broken Rotor Bar Detection in Closed Loop Inverter Fed Induction Motors Through Time-Frequency Techniques

In traction, automotive, and some industrial processes, the operation of the induction motor is set using speed. This creates an additional control loop that is external to the current controller that inverters already possess. While the impact of the latter control loop on fault detection in induction motors has already been studied, the influence of closed-loop speed control has not been explored enough. This paper presents the findings on the impact of PID speed control on the broken rotor bar fault detection. The study reveals that the constant corrective actions of the PID controller to correct the speed cause an increase in the noise level and spectral leakage around the first harmonic in the stator current spectrum that prevents fault detection. It is concluded that it is necessary to use time-frequency analysis techniques with excellent spectral resolution, such as the Dragon Transform or the Min-Norm technique.