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480 corner grounded delta and generator

480 corner grounded delta and generator

480 corner grounded delta and generator

(OP)
I have a customer that aquired two 130kw 480 wye generators for possible use at some water tower sites. The utilty provider is coming in with 480 delta corner grounded c phase. The only loads are the pumps and a smaller transformer running heat and air, control and a light. The generator cannot be configured to the 480 delta per manufacturer. The only solution i have come up with is pulling the pump, and changing them to 277/480 wye, and changing the transformer for 120 loads to match, then have utility provider install the 480 wye as well. Does anyone have another solution that could be cost effective?

RE: 480 corner grounded delta and generator

Motors don't know from Wye or Delta as far as the SOURCE is concerned. If the motor is configured for 460V, then it is going to take 460V, phase to phase. Nothing inside of the motor is reference to neutral and the rest is irrelevant. You are fine.

The bigger issue would be if you were going the OTHER way, i.e. the service was Wye and the generator was Delta, because the service equipment (panels, breakers etc.) might not be rated for use on a Delta source. But given that it is ALREADY Delta from the utility, the equipment (ostensibly) is already good with it.

Hopefully there are no VFDs on those motors though...


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

RE: 480 corner grounded delta and generator

(OP)
So those were my thoughts originally as well. The motors dont appear to have vfd. However there is something going on when we transfer to gen, the motor tries to start and kicks out within seconds. There is a transformer that runs the basic circuits inside well house, that i believe is wired as delta. The issue is the 480 from generator is not corner grounded, no neutral is used either. I am thinking that the transformer may be the piece having the problem.

RE: 480 corner grounded delta and generator

Your generator probably has the neutral grounded as the default connection.
Are you sure that the supply is not four wire delta with a center-tap ground?
Is there a second corner ground connection in the panel?
If so it is not a good idea to remove it and may be a code violation.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: 480 corner grounded delta and generator

(OP)
yes the supply is a 3 wire. I can clearly see it coming overhead and see it at the connections. it is a corner grounded delta on c phase.

RE: 480 corner grounded delta and generator

Check your generator for an internal ground on the neutral. That is quite common.
If you have a neutral ground fighting a C phase corner ground the generator may be damaged already.
If the generator has been damaged by dueling grounds then "the motor tries to start and kicks out within seconds." may result.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: 480 corner grounded delta and generator

Ask the utility if they will remove the corner ground and center ground one transformer. That will also protect the bank just moving the ground down.
And your generator will work.

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