Fault Harmonics Current Detection in Closed-loop Controlled Induction Motors

Inverters are used to supply induction motors in the industry and electric traction. Inverters can operate in open-loop or closed-loop control. This work aims to study how the control mode affects fault detection and observation in the stator current spectrum of winding and rotor slot harmonics. We present an experimental study on these effects. In closed-loop control, the steady-state analysis of the stator current with the Fourier transform is unsuitable due to slight variations in the motor speed and the supply voltage frequency. It is necessary to use a time-frequency analysis technique. In this case, the short-time Fourier transform is used, which is well adapted to slow speed and frequency variations. It allows observing the trajectory in the time-frequency plane of the fault, winding and rotor slot harmonics.