2022 Fault Zone Series: Part 3 Insulation

Returning to the Fault Zone approach to electric motor troubleshooting we continue this series with Insulation. When PdMA refers to the Insulation Fault Zone in an electric motor, it is referring to the dielectric properties of the ground wall insulation to prevent current flow to ground. When a motor develops a ground wall insulation fault, excessive current is passing through the insulation to ground. This leads to localized heating and possible failure of the electric motor.

A variety of root causes should be considered following an insulation failure or ground fault trip. The Insulation is often a final mode of failure as a symptom instead of the root cause. The following are some potential root causes to consider:

  • Overload – Excessive Heat
  • High Resistance Connection – Localized Heating
  • External Contamination – Moisture/Conductive Material Intrusion
  • Design Flaw – Insufficient Cooling/Air Flow
  • Environment – Excessive Ambient/Chemical Attack
  • Excessive Vibration – Excessive Friction
  • Space Heater Failure – Humidity Intrusion

Although shutdown opportunities can be limited, de-energized testing of the insulation system is critical to identify a reduction in insulation integrity early in the PF Curve so the problem/root cause can be isolated and corrected.

For more examples of insulation anomalies and alarm standards applied to your electric motor reliability view Fault Zone Analysis Insulation on the PdMA YouTube channel.