Dear all,
I have a 3-phase, 400V, 50Hz 75kW submersible waste water evacuation pump that was installed two months ago in a sump. When the pump was delivered, we took measurement of the insulation resistance of its motor, and the values between phases and between the phases and earth was greater than 999mega-ohms. However, we observed that when the pump was installed and run, it was tripping on overload with the setting at 70A. We then increased it in steps until it stopped tripping when the setting was 80A. The starter system is star-delta.
However, we recently observed that the pump was tripping on overload and when we shut it off and took the insulation resistance measurement, the values we got were about 3 mega-ohms between phases and between phases and earth!!!!
Can anyone tell me what may have been the cause of this failure/tripping/low insualation resistance and recommend remedial action that I can take? Please treat as urgent. Best regards
