AEGIS® Shaft Grounding Ring for DC Motor

DC motors when operated on drives may also require bearing protection from induced shaft voltages. Capacitive induced shaft voltages may be hundreds of volts peak-to-peak and depending on the drive will increase in amplitude as the speed of the motor is increased.

If there is no shaft grounding ring installed, the voltages may discharge through the bearings causing EDM pitting and fluting failure. In addition, circulating currents from magnetic dissymmetry may exist on DC motors over 10 HP (7.5kW) This would necessitate the insulation of the NDE bearing, with an AEGIS® Shaft Grounding Ring installed on the opposite end of the motor.


  • To prevent bearing failure install an AEGIS® SGR on the DE of the DC motor for all motors up to 300 HP (225 kW). For DC motors over 10 HP (7.5 kW), also insulate the NDE bearing.
  • Large DC motors over 300 HP (225 kW) have higher shaft voltages and currents and require the AEGIS® PRO Series installed on the DE of the motor.
  • In addition, the NDE bearing should have insulation to prevent circulating currents.

For information and how to order, please contact us on  +44(0)1792 763000

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