11. When should the motor have a current-insulated bearing?

In general, it is difficult to eliminate the causes of current transmission damage to the ball bearing in an electric motor. In most cases, this occurs with larger frequency inverter driven motors. However, this type of bearing damage can be avoided if the motor's internal current flow to the bearing is interrupted. This is possible through the use of current-insulated rolling bearings. When using frequency inverter-controlled electric motors over 75 kW (IEC280), we recommend installing a current-insulated bearing on the fan side (B side).