Problem diesel generator supplying submersible pump

Thread Starter

Vlad Vsky

Joined May 15, 2017
I have a diesel generator 30 KVA , max current 43.5 A, and a motor of 7.5 KW (10 HP), max current 16 A training a submersible pump.

I tried to supply the motor by the generator, but at the start up the generator vibrates then it shuts down.

Conclusion: The motor draws an inrush current that the generator can't supply.

However the motor was supplied using this generator for 4 years.

Conclusion 2: The generator got a bit deteriorated and it can no longer deliver the same power at the start up.

I will be thankful to know your opinions.


Joined Feb 20, 2016
Can you test the pump on aifferent supply?
I wonder if the fault is in the pump. If it has been running for 4 years, it may need some maintanance.


Joined Feb 8, 2018
I agree that there may be something wrong with the pump.

The vibration suggests that there may be something wrong other than simple overload.
One possibility is an issue with the speed governor for the generator engine.
If this is a three-phase generator, something wrong with one of the phases, anywhere between the generator itself and the pump motor, may be causing the problem.

Thread Starter

Vlad Vsky

Joined May 15, 2017
Thanks for your answers.
We found out that the problem was within the pump, it was full of dust, plastic, ... a deterioration of the rings.

I would like to understand something.
When the motor(which is attached to the pump) starts it draws 6 times the rated current, and the voltage drops. So what's important about the sizing of the supplying generator, is that it can deliver at the starting moment enough power in KVA.

The generator is 30 KVA with a rated current of 45A. and it could supply the motor, which is actually 15 HP (11 KW) and it's rated current is 24A.
so: 30KVA is sufficient to start 15HP motor

But according to the NEMA code in the link bellow, to size the genset, we multiply the 15HP by a factor of 5.6, so we need 84KVA at the starting moment.

Can anyone give an explanation please ?