Genset is surging too much

emcc

I have a 40KVA Diesel Gen Set. Powering induction motors of following capacity:

2 x 15HP rated at 415VAC
1 x 3HP rated at 415VAC

1KW misc. load

My gen set feels too much loaded when everything is working. Gen set is being driven by a 6 cylinder engine. I want to know, if I upgrade to a 62KVA Genset, will it also surge?

Cariboocoot

Re: Genset is surging too much

emcc wrote: »

2 x 15HP rated at 415VAC
1 x 3HP rated at 415VAC

These numbers do not make sense. 415 Volts Alternating Current? or 415 Volt Amps?

A 15 HP motor would be about 12,000 Volt Amps. A 3 HP motor would be about 2300 Volt Amps.
Normally we'd expect the 15 HP motors to be 3 phase, 208 Volt. A 3 HP motor could be single phase 240 Volt.

That aside (i.e. assuming they are Voltage and phase matched), the two 15 HP motors should be pulling around 24 kVA plus the 3 HP and you are definitely in the 30kVA range, or 75% of your generator's capacity. Through in the typical motor's power factor and the miscellaneous loads and I'm sure that generator would be feeling the effects. Increasing to a 62kVa genset would decrease the load to about 50% and should ease the burden on the gen. But then you get in to the issue of "is it loaded enough"?

At this point, double check the numbers on the loads and the generator (including the run time; it may be worn).

inetdog

Re: Genset is surging too much

A working voltage for motors of 415Volts (50Hz) is not uncommon outside the US.
In the corresponding US (NEMA standard) motor, the nameplate voltage would be 460 volts and the motor would actually be driven from a 480 volt supply.

If the power factor of the motor is very low, it might cause more surging as the generator tries to regulate. If that is the case, an appropriately sized power factor correction capacitor connected across the motor terminals might help. The capacitor should be wired so that it gets disconnected from the generator when the motor is turned off.

emcc

Re: Genset is surging too much

Figures are correct. Motor name plate says:

Make: Crompton Greaves
Volt: 415 + 10%
HP: 15
kW: 11
RPM: 1460
Eff: 84%

Blackcherry04

Re: Genset is surging too much

Keep a open mind, looks like they make all kinds of special application motors at any voltage you want.

http://www.cgglobal.com/frontend/Category.aspx?cnl2=GGnZBTXjfns=

Cariboocoot

Re: Genset is surging too much

So what part of clarifying the difference between the Voltage of the motor and the Volt Amps they use didn't you guys understand? Voltage alone is only half the issue, and the mechanical HP rating of the motor doesn't complete the picture either. You really do need to know the current and the phase to understand the whole.

As it is, judging by the additional info supplied by emcc my original evaluation appears to be correct: he's using around 75% of the generator's capacity, probably more. So yes a larger gen would be more stable against the loads but as I also said you can then run into the troubles associated with not loading it enough.

Not all generators are the same either. Nor do they last forever.

emcc

Re: Genset is surging too much

I am sorry but why not loading the generator enough is a problem?

Cariboocoot

Re: Genset is surging too much

emcc wrote: »

I am sorry but why not loading the generator enough is a problem?

If it isn't loaded enough the engine will run at less than optimum temperature. Do some research on "wet stacking". Basically too much fuel that's not getting burnt leading to carbon fouling problems. This usually happens at less than 50% loading.

ChrisOlson

Re: Genset is surging too much

Cariboocoot wrote: »

These numbers do not make sense. 415 Volts Alternating Current? or 415 Volt Amps?

No, it's 415V three-phase. Three-phase voltage in IEC countries (essentially everywhere but North America) used to range from anywhere between 380-415V, with the phase-neutral voltage being 220-240V. England was primarily 240/415, while the rest of Europe was 220/380.

They passed a new standard in the EU (2006) to 230/400V, but that is still mostly theoretical and for new installations. There really hasn't been a change in what the utilities produce, just in the labels put on equipment. The 230/400V is a compromise that allows the different distribution voltages to fall within design tolerances.

The UK is still primarily 240/415 today.

Anyway, emcc -
Your genset, if it's a prime power unit, is loaded about right. If it has a surging problem it can be caused by varying loads on your electric motors, or a governor problem on the genset. What genset are you using, and what engine does it have on it?
--
Chris

Cariboocoot

Re: Genset is surging too much

I am writing in English, aren't I? Haven't slipped into some language not known on planet Earth?

emcc

Re: Genset is surging too much

Genset Alternator is from Kirlosker and is being run by a TRUCK Engine TATA 608. That's how our Generators work.

ChrisOlson

Re: Genset is surging too much

Well, there's your problem. Unless you changed the injection pump or put a belt drive Paxton or similar governor on the injection pump lever, automotive diesel engines do not use full-range governors. They have limit governors and are not suitable for stationary generator use.
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Chris

emcc

Re: Genset is surging too much

I checked the current flow today with a Clamp Meter, the starting current for one 15HP motor is approx 22.6. And running current with all the equipment running is around 30A at 420V

ChrisOlson

Re: Genset is surging too much

That part is all fine. But using an automotive engine you have a limit governor, or otherwise called a "min/max" governor. It does not control engine speed within a certain deadband range under various loads at anything other than idle or full throttle operation. There is no intermediate control of fuel rack position except by changing the position of the throttle lever. That type of governor, while it works excellent in automotive applications, does not work well on a genset.
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Chris