Wye generator to Delta Load

[tom baker]

I had a question from a designer and I wanted to pass it on to the forum. He has a Wye connected generator, and wants to use it via a transfer switch to a delta system. The designer was wondering what to do with the neutral. Apparently, the generator is only available in a wye connection.

 

[hillbilly1]

I know of a sewage lift station that is set up this way, it seems to work, I don't know who originally installed it. It looks like the undervoltage setting on the transfer switch would have to be set low, or the switch is originally set up for a wye connection. Either way, probably violates the UL listings. There is probably a longer lead time to get the delta wired generator. The Kohler that I have is easily converted by changing the winding connections (It is convertable to 120/208 wye,120/240 delta,277/480 wye). Must be a no name brand or a Generac.

 

[LarryFine]

Tom, is the present service grounded?

 

[tom baker]

No, its an ungrounded delta with ground detection

 

[LarryFine]

I would imagine that just bonding the neutral at the transfer switch would work.

 

[Cold Fusion]

I had a question from a designer and I wanted to pass it on to the forum. He has a Wye connected generator, and wants to use it via a transfer switch to a delta system. The designer was wondering what to do with the neutral. Apparently, the generator is only available in a wye connection.

I'm assuming the system is ungrounded 480 delta, and the gen is 480/277 Wye. Nothing else fits very easily.

Check the mfg specs - or call them. See if they say that the neutral has to be grounded. If you call, the way to ask is, "Is a high impedance grounded neutral is okay? If they say, "yes", ask if ungrounded neutral is okay. If the mfg specs say it is okay to leave ungrounded, then don't ground it. Just connect the gen as a delta. The gen won't care nor will the system.

cf

 

[Cold Fusion]

... The Kohler that I have is easily converted by changing the winding connections (It is convertable to 120/208 wye,120/240 delta,277/480 wye). ...

Interesting. A gen with 120V coils and you can connect it for 277V. I don't think I have ever seen one like that before.

I guess Kohler could have made the gen with 139V coils and then let the gen VR go down 120v. That would work. Is it possible that your Kohler will connect for 480V Delta, not 480 Wye?

cf

 

[SG-1]

If the generator X0 is bonded to the enclosures, then upon the first ground fault the OCPD will operate. Can the system tolerate shutdown upon the first fault ?

 

[Cold Fusion]

Again, still thinking the system is 480D. Just thought of something else. Is the system corner grounded delta?

cf

 

[SG-1]

No, its an ungrounded delta with ground detection

Not corner grounded. I was wondering the same thing when I read the first post. That would have been a quick shutdown.

 

[Cold Fusion]

Of course - what was I thinking? I read that too.:-?

cf