A non intrusive methodology for bearing current detection in PWM inverter fed induction motor drive

Application of pulse width modulation (PWM) inverters fed three phase induction motor drives are increasing now a day in industry, due to their energy saving property. However, such motors are prone to generation of bearing current which causes bearing wear through electrical discharge machining (EDM). Present methods for diagnosing bearing current are based on vibration spectrum analysis, monitoring the waveform of the shaft voltage or monitoring the current flowing through the carbon brush placed between the shaft and the motor frame. These techniques, requires mandatory site inspection and special arrangement for data collection. As a result, these methods are not feasible in all industrial cases. Therefore, development of an alternate non contact and non intrusive technique is required to easily detect the presence of bearing current. This paper proposes a method to effectively detect the presence of bearing current using motor current signals only. These signals could be easily collected from the motor control panel itself. The proposed method does not require any site inspection or additional fittings, which makes it applicable for every industrial scenario.