45kw generator 480v 3 phase hookup

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RUWired

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Cold Fusion said:
See if this sounds better:
If the plant 480V system is grounded Y and is bonded at the main switchgear, and you use a 3W transfer switch to the gen:
Then the gen neutral needs to be connected to the plant neutral, and the gen frame is connected to the plant grounding system, and no neutral/ground bonding jumper at the gen. For this case the gen is not an SDS.
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CF forget the neutral conductor. It's not needed with a 3-wire transformer primary. We don't even know if the bus duct has a neutral. Unless the OP is feeding other equipment down stream of the ATS, the equipment ground conductor with the feeder to the transformer via the ATS will carry the fault current back to the gen set. With no solid tie to the utility the gen set becomes a SDS.
CF said:
Even though not used, the gen neutral must be connected. Otherwise, when running under the gen a ground fault will not get back to the gen neutral and trip a CB.

cf
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The equipment ground conductor will acomplish this as well with the system bonding jumper installed.

Rick
 
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RUWired

Senior Member
Location
Pa.
benaround said:
Anyone else feel this gen. is too small for the load ? 45000/480/1.73= 54 amps, gen.

supply. I mean just the 112.5KVA transformer @ 480vac side =135 fla., I think a good load

calc. needs to be done if it hasn't been done already. jmo.
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Frank is the inrush current based on the secondary load times the ratio of the transformer times 10?

Rick
 
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Cold Fusion

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RUWired said:
CF forget the neutral conductor. It's not needed with a 3-wire transformer primary. We don't even know if the bus duct has a neutral. Unless the OP is feeding other equipment down stream of the ATS, the equipment ground conductor with the feeder to the transformer via the ATS will carry the fault current back to the gen set. With no solid tie to the utility the gen set becomes a SDS.


The equipment ground conductor will acomplish this as well with the system bonding jumper installed.
Yes, if you install a neutral/ground bond at the gen - cf

Rick
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You want to connect a system bonding jumper (gen neutral/ground bond) at the generator? Okay. For some reason that ties my brain in a knot. Something about two system bonding jumpers.:-?

Yes, I understand that the generator neutral is not needed or connected. Yes, I understand the plant neutral is not connected to the transformer.

You're right, it would be plenty safe since the plant neutral is not connected to the gen neutral. There is no parallel path. One could look at it as though not having the gen neutral connected is the same as having a 4W switch. There are two N/G bonds, but the two systems don't touch. The two neutrals don't touch.

You have the science on your side. I just have to get my head wrapped around the code issues - (Did I just say that? It must be my evil twin typing:roll:)

cf
 
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