Measuring insulation resistance is a basic check of the condition of the winding. It is the first to show whether the insulation is healthy or the engine is at risk of breakdown. Let's look at how to measure insulation resistance with a megger.
What the measurement shows
The megger supplies high voltage to the winding and measures the resistance between the winding and the housing (and between the windings). Low resistance means leakage - due to moisture, contamination or destruction of the insulation.
How to measure
- The motor is de-energized and disconnected from the network.
- Select the megger voltage according to the voltage class of the motor.
- Connect between the winding terminal and the housing.
- Take a reading after 60 seconds.
What it says result
| Resistance | Output |
|---|---|
| High (normal) | Insulation healthy |
| Reduced | Moisture or contamination - need drying |
| Close to zero | Insulation breakdown - need rewinding |
The absorption coefficient is also important - the ratio of readings for 60 and 15 seconds, showing the degree of moisture.
What to do based on the result
If the resistance is reduced due to moisture, drying helps windings. In case of a real breakdown, rewind is required. Regular insulation measurements are the basis of prevention, part of full diagnostics.
Do you need to check the insulation of motors at an enterprise in Tashkent? Elektromotors engineers will take measurements and give an opinion - contact us.