What are the reasons why the motor of the sewage lift pump trips easily?
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This post was last edited by chendehan69 on 2020-4-2 at 15:46. A submersible centrifugal pump is installed in the wastewater regulation tank; its rated head is 20m, and the rated flow rate is 50 m3/h. The motor has a rated current of 28.7A, and the outlet pipe diameter is dn100mm. A butterfly valve is installed on the outlet pipe, which is usually kept fully open. There have been no instances of motor tripping failures. Two months ago, the impeller of this pump failed, so the entire unit, including the motor, was removed and a new temporary pump was installed. This new pump also has a rated head of 20m; its motor has a rated current of 41.5A, and the rated flow rate is 100 m3/h. Similar to the old pump, the outlet pipe diameter is dn100mm, with a butterfly valve installed on the outlet pipe. When the new temporary pump was in operation, its outlet butterfly valve could only be opened to 1/4 of its full position; opening it a little further caused the motor to trip after operating for a short time. It’s still the old wiring for the pump motor. May I ask everyone, what is the reason for this?
It’s still the old pump motor circuit.
When the newly installed motor has a higher power rating, the flow rate also increases. In such cases, a trip occurs. The likely reason is blockage in the discharge pipeline, which leads to increased resistance and higher discharge pressure; as a result, the motor needs to generate more driving force, exceeding its rated power level. This increases the current, and thus a trip occurs! ! ! Did the impeller fail due to deformation caused by collision with the casing?
Hasn’t the rated current of the current protector been changed? It trips at 28.7
But what does it have to do with the previous impeller failures?
The old pump has a head of 20m, while the new pump has a head of 30m.
According to the electrical technicians, when the new pump is in operation, the motor current reaches around 40; the reason for the pump tripping is likely an overcurrent trip.
It can be confirmed that the outlet pipeline of the new pump is not blocked. There is no rubbing on the impeller either.