Application of Static Charge Dissipation to Mitigate Electric Discharge Bearing Currents

Today, the physical cause-and-effect chains of inverter-induced high-frequency bearing current have been well understood, but little has been known on not only theoretically possible, but cost-effective mitigation techniques for a certain drive configuration. This paper focuses on the mitigation of discharge bearing currents, which occur predominantly with smaller motors of up to several kWs. We present a new mitigation technique where any voltage build-up across the bearing is discharged via static charge dissipation through a parallel path before an electric breakdown inside the bearing occurs. The technique is based on the field emission effect, has no direct frictional wear, is free of maintenance, and robust towards contamination.