Purpose:
Verify that the conductor's outer coating is intact and not shorting to the ground or another conductor.
Voltage Level:
- Use the motor's circuit voltage rating
- Double the testing voltage on the insulation tester.
- Example: For a 480V system, set the tester to 1000V
Ohm Readings:
- Ideal guidelines come from the motor manufacturer or electrical codes.
- If unavailable, use this rule of thumb
- Below 1M ohm: FAILURE
- Above 1M ohm: GOOD
The higher the reading, the better the insulation integrity.
Using the Insulation Meter:
1. Short Circuit Test:
- Connect the test probe with three terminals into the matching input jack.
- Attach alligator clips to the other ends and join them to create a short.
- Press and hold the "Yellow Insulation Test" button.
- Display should show 1V and 0.0 ohms
2. Open Circuit Test:
- Ensure the test probes are not touching.
- Press and hold the "Insulation Test" button.
- Display will show the selected voltage and the highest ohm value it can measure.
- Example: at 1000V, the Fluke-1587 FC can measure up to > 2.2G ohms.
- Good results: 1M ohm to > 2.2G ohms.
- Below 1M ohm: Failed Test
Below is a table created by The International Electrical Testing Association (NETA) as reference.
