voltage fluxuation

[ceb58]

OK need ideas. 25kw Generac gen. set. When the load is transferred to gen. the voltage starts fluctuating 215-250v L-L .With out load it holds 242v with no change. My first thought was loose connection checked termination in ats, good. Connections in disco. was able to get about 3/4 of a turn on all terminals. Tried it again same thing. Was going to check terminations on breaker in gen. set but it started raining like crazy. There is also a 12kw UPS on this system. I opened the main breaker to isolate the UPS from the system and it made no difference in the fluxuation. I ohm'ed all wireing out nothing. The only thing I found strange was at the gen. disco the contractor installed. The gen. set has a 125amp breaker the contractor installed a 200amp rated fusible disco. with 200amp fuses. I could read .83 ohm's L-L at the disco. My thought now is the voltage regulator. Any other ideas?

 

[Cold Fusion]

...My thought now is the voltage regulator. Any other ideas?

Nope, That one sounds good to me.

Have you got the MFGs literature? If not you may wish to give them a call and see if it is available - maybe on the internet.

cf

 

[LarryFine]

Achmed, does the engine itself vary in speed as well? Have you checked the output frequency?

Have you checked the running voltage at the generator itself? That would eliminate most of the installation quickly.

I have seen a 7kw Generac hunt (vary in speed) if too-lightly loaded.

 

[Cold Fusion]

Achmed, does the engine itself vary in speed as well? Have you checked the output frequency? ....

Larry
Are you suggesting the gen is an inverter type? Otherwise the engine speed and the gen frequency are sort of locked.

cf

 

[RESI]

ceb58

Ziller Electric has a forum for Generac generators. Just google Ziller Electric and it should lead you to the forum.

 

[ceb58]

Achmed, does the engine itself vary in speed as well? Have you checked the output frequency?

Have you checked the running voltage at the generator itself? That would eliminate most of the installation quickly.

I have seen a 7kw Generac hunt (vary in speed) if too-lightly loaded.

By the display the Hz are not fluctuating, the engine (diesel) is maintaining a Constance speed. The amp draw on the building is in the 50-60 amp range. This is why I isolated the UPS from the system we have had some that the UPS kw to gen. kw ratio would make the gen set go stupid.
I will go back next week to get to the breaker to check voltage could not do it yesterday due to it raining cats and dogs.

 

[LarryFine]

Larry
Are you suggesting the gen is an inverter type? Otherwise the engine speed and the gen frequency are sort of locked.

Inverter, no. I expected the speed/frequency relationship, which is why I asked.

By the display the Hz are not fluctuating, the engine (diesel) is maintaining a Constance speed.

Then it's not mechanical, and thus must be electrical or electronic. If the phase-to-neutral voltages are equal, it's likely not electrical, and thus must be electronic.

I suspect a voltage-regulator issue.