[Question] Generator thats hunting

[Ivanjvv]

Good day

I have a 20kVA generator conected to a lister engin and a 2.2kw 3phase motor. I asume that the AVR is blown and dont know how to test it? It gives out 400V, but as soon as you start the motor the voltage drops to 300V till the engin cuts out.

The motor is fine, as I did test it with portable generator. I have had issues before with generators hunting and dont think it is that.

Any ideas what and how to resolve this issue?

[GCE]

Hi

What size was your portable generator ?

Looking at your 2,2 kW motor with a direct on line start I would estimate the start up to be equivalent to at least 13 KW and possibly 18 KW

The fact that it runs on one genset and not the other I would guess that the Lister engine KW output ( mechanical rated) to the alternator is not sufficient to handle the start up and basically stalls the Lister motor .As the Lister motor slows down so the voltage will drop.

[Justloadit]

If the AVR was faulty, the output voltage would drop yes, but it would not load your diesel engine to the point it cuts out.
It may be that you have an engine problem, dirty injector, or blocked fuel filter, or even dirty air filter.

Do you have circuit breakers in series with your motor?
What size are they?
Have you tested the motor to see that the motor does not have an internal short or earth fault?
Have you tested the motor on mains?

[Ivanjvv]

Good day

My portalble generator is 22kw 3 phase. The lister engin has been servised as that was the first thing I let the machanic do. It all use to run well apparently.

There are breakers in line yes. The generator has a 32A breaker in and the MCC has a 25A mains breaker. Overload is set to 5.8A, as it is a borehole motor.

The 2.2kw motor tests fine over all 3 windings and is not down to earth on a 1000v. The Amp alsi ballanced on plus minus 8A while testing it at 300V for about 5 seconds.

I have not tested the motor on mains due it being in the mountains on the leshoto boarder feeding water to a village. There is no electrical supply in that area.

We have about 13 boreholes there and 6 of them is exactly the same sizes. 2 of them having the same issue. The machanic says it "IS" an electrical issue and dont want to swop out engins nor generators. Thats why I used the portable geni just for testing purposes.

So I wil be going there sometime next week again to test the MCC and generator with an inductive motor that is 3.7kw. It sould run without issues, as it wont have any load and the borehole motor runs at 5.8A. Will be connected star/delta and shouldn't pull more than 5A with no load .

What I really would like to know is how does the AVR work, as it has 2 wires that test the voltage and 2 wires that goes somewhere into the windings, marked F+ and F-. Had to excite another generator with those wires, as the generator was standing for a year with nothing in. Just the generator was standing there as the engin went in for a repair.

Hope you guys enjoy the day.
Ivan

[Justloadit]

A 2.2KW 3 phase submersible motor is usually rated at 5.5Amps at full load.
A 3.75KW 3 phase submersible motor is usually rated at 9.0Amps at full load.

In a bore hole environment, using a generator which is not at least 3 times larger than your motor, will not get the motor started. A centrifugal pump only starts loading the motor when it reaches approximately 1000RPM, so the motor really has no load at start up. In these conditions if all is well, the motor will be at full RPM with in 8 cycles, so the generator should be able to not die on you if it is a minimum of 7.5Kw, but I would not guarantee that it won't. Too many factors, I would say a minimum of 11Kw to be on the safer side.

[Ivanjvv]

The 3.7kw motor is not a submersible motor. Its a normal motor and pulls almost 5A at no load.