Motor Current Signature Analysis of a Variable Speed Drive for Motor Fault Diagnosis

The induction motor is one of the most used electric machines in the industry because of its strong and simplicity. This paper investigates the performance of conventional techniques such as sideband analysis in detecting broken rotor bars when the motor is fed from a common pulse width modulation voltage source inverter PWM-VSI drive for variable speed drives. The phase current signals are obtained under both the slip compensation mode and non-compensation mode. The spectra are compared between the healthy and faulty motors in the frequency domain. For the non-slip compensation, it has shown clear sidebands of the twice slip frequency which allows the detection of the broken bar and hence rotor faults under different speeds and higher loads. However, for slip compensation, the sideband pattern does not exist anymore and hence new features have to be investigated for fault detection when motors operate under these operating modes.