Regularly scheduled and trended insulation resistance (IR) testing can tell you if motor insulation is starting to fail. But relying on IR testing alone is risky. Motor winding insulation also comes under attack from heat, vibration, and overvoltage. To detect those causes and perhaps intervene you should follow these guidelines:
- Thermal trending and alarming alert you to a condition that is deteriorating, though below the level where it triggers motor overload protection devices.
- Vibration monitors can alarm on high vibration. But you should also be trending vibration data (predictive) and using handheld vibration analyzers (spot checks).
- To see if overvoltage has damaged the insulation, use DC potential and/or surge tests.
- Set your power monitor to alarm upon undervoltage or overvoltage, so you know when motors may be at increased risk.