Premature wear and recurring bearing failures in an inverter driven induction motor — Part I: Investigation of the problem

This paper provides an analysis about early incipient failures in three-phase induction motor bearings when driven by PWM inverters, focusing on a real industrial process. The preliminarily defined potential problems were firstly discussed on a theoretical basis and afterwards experimentally assessed by means of vibration, stator current and common mode current data acquisition and analysis. Following the investigation, it was concluded that the presence of common mode currents at the verified levels could cause damages to the motor bearings. This result could be confirmed when the machine stopped working due to another failure of the bearings.