Broken rotor bars diagnosis in an induction motor fed from a frequency converter: experimental research

Rotor electrical faults are common types of faults in squirrel cage induction motors (IMs) and have been investigated in detail under steady state conditions for direct mains-fed machines. Motor current signature analysis (MCSA) has been widely reported in the literature as a suitable fault diagnostic technique for directly-supplied IMs. However, when an induction motor is fed from a frequency converter composed of a rectifier, DC link filter and a PWM inverter, its characteristic signals (currents, voltages, electromagnetic torque, etc.) become very noisy. This paper presents an experimental analysis of a damaged squirrel cage induction motor supplied from an industrial frequency converter at different speed and load levels. The main purpose is to experimentally study the ability of the MCSA to diagnose the occurrence of broken rotor bars under these operating conditions.