Troubleshooting and fixing of inverter driven induction motor bearing currents in existing plants of large size - an evaluation of possible mitigation techniques in practical applications

The effect of bearing currents in inverter driven induction motors has been investigated and reported for about ten years. Mitigation techniques have been developed and approved by experiments. In this paper, the special situation of troubleshooting in a given configuration such as existing large plants is discussed. The determination of the actual bearing current phenomenon and the development of the appropriate mitigation technique under given circumstances are shown. A new equivalent circuit diagram for the bearing currents in large drives has been developed and used for evaluation of mitigation techniques. Experiences applying the mitigation techniques to a drive suffering premature damages due to rotor ground bearing current are presented and discussed using experimental results