Shaft Voltage Measurement

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What is EDM (Electrical Discharge Machining)?

  • The pulses to the motor from the VFD create a capacitively coupled common mode voltage on the motor shaft
  • The voltage looks for a path to ground, breaks down the dielectric in the bearing. The voltages arc through the bearings, and electrical discharge machining (EDM) creates thousands of pits
  • Bearings degrade, resulting in increased friction and noise
  • Eventually, the rolling elements can cause fluting damage to bearing races
  • Bearing lubrication/grease deteriorates, is burnt and fails
  • Potential for costly unplanned downtime

Image of a bearing affected by EDM.

 

How is it measured.

The severity is measured using a Scope Meter,  voltage probe and AEGIS® SVP Shaft Voltage Probe Test Kit.

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