Delta Wye step up transformer in reverse.

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alblock

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Location
NC, TN, SC
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Industrial Electrician
The company i work for bought out a company that was closing shop. One of the items was this 3p 15kva delta wye step up transformer 200v to 480/277. We have 480/277, so unless i can use this in reverse, we would only need it in a rare situation.

Can this be used in reverse?
Would the kva rating change?
What about the neutral?
Bonding?

Thanks

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alblock said:
The company i work for bought out a company that was closing shop. One of the items was this 3p 15kva delta wye step up transformer 200v to 480/277. We have 480/277, so unless i can use this in reverse, we would only need it in a rare situation.

Can this be used in reverse?
Would the kva rating change?
What about the neutral?
Bonding?

Thanks
Click to expand...

Yes it could be used in reverse but you would need a specific application because you would not have a neutral and would need to corner ground it or use ground detectors. Kva would stay the same.
 
Looks like a step down to me.
But with the lots of taps you should be able to get the volts you want/need.
 
ActionDave said:
Yes it could be used in reverse but you would need a specific application because you would not have a neutral and would need to corner ground it or use ground detectors. Kva would stay the same.
Click to expand...

I wouldn't connect anything to H0, is this correct?

Besoeker3 said:
Looks like a step down to me.
But with the lots of taps you should be able to get the volts you want/need.
Click to expand...

I know the second image is hard to see but T84H15S is the catalog number. Info on 5th page. Connection #16 is on the last page.
https://stevenengineering.com/pdf/39XFMR_GP_OLD.PDF
 
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It can probably be used in reverse, but what would be the point?
Why would you ever use 208 volts for 3-phase loads when 480 is available?

The only situation where it would be useful in your shop is if you had a 208-volt 3-phase load that can't be reconfigured for 480,
or more 208-volt single-phase loads than your existing 120/208-volt transformer can handle.

Put it up for sale tomorrow. Don't make your next of kin liquidate it.
 
drcampbell said:
.... Don't make your next of kin liquidate it.
Click to expand...
Have you been talking to my wife? She has been using those same words a lot lately...

But I agree, it MIGHT be useful if you had any 3 phase 208V loads that you needed to power, but it cannot be used as 208Y120 4 wire, which is what most people EXPECT in a 208V system, so you would also run the risk that some future user would not read the transformer label and ASSume that if it reads 208V phase-to-phase that it must be 120V to Neutral and they would damage something. Not worth the risk.

Put it up for sale or sell it to a used equipment broker. There is a decent demand out there from people who have 208V services and get a 460V machine that can’t be changed. We see them in here quite a bit, wanting to know if a transformer like the one you have exists.
 
I suspect the place we got the equipment from only had a 208v service. The compressor I got running today had a 200v 3 lead motor. I used a spare 45kva 480 to 208/120 transformer we had. This transformer is a 208v step up. I'm gonna wait and see what other equipment we get and if I can't find a stand alone use we will sell it. Thanks again everyone.
 
Jraef said:
you would also run the risk that some future user would not read the transformer label and ASSume that if it reads 208V phase-to-phase that it must be 120V to Neutral and they would damage something.
Click to expand...

You know what was said in the movie "Under Siege 2" about assumption...
 
Transformer needs to be identified for that use, there was a change a few code cycles ago on this.
Normal is Delta Wye
You end up with Wye Delta.
The delta secondary needs to be grounded, See section in 250 on SDS, you could use a corner ground..lot of work when you can get the correct transformer
 
electrofelon said:
that fed a wye delta (delta wye used in reverse) and they run a neutral with the supply instead of leaving it floating.
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That part I had figured out, how did you get that excessive heating to destroy a portion of the raceway? Must have been a neutral to case bond making the raceway a parallel path back to source and then a weak spot in that fitting and heat build up there?
 
kwired said:
That part I had figured out, how did you get that excessive heating to destroy a portion of the raceway? Must have been a neutral to case bond making the raceway a parallel path back to source and then a weak spot in that fitting and heat build up there?
Click to expand...

Yup. I noticed the situation, and removed the neutral conductor, but I didnt notice there was a jumper between X0 and the case (it was in a dark real awkward spot) so that remained in place. When I came on site after the incident, the EMT had failed as you see and a utility phase had failed at the pole. I think that utility connection failed and thus caused the severe imbalance on the transformer supply conductors.
 
electrofelon said:
Yup. I noticed the situation, and removed the neutral conductor, but I didnt notice there was a jumper between X0 and the case (it was in a dark real awkward spot) so that remained in place. When I came on site after the incident, the EMT had failed as you see and a utility phase had failed at the pole. I think that utility connection failed and thus caused the severe imbalance on the transformer supply conductors.
Click to expand...
That helps explain the raceway problem, if it were a parallel path it would have been high enough resistance the neutral would have carried the bulk of current. When you eliminated the neutral but missed the bonding jumper - the raceway was apparently the only neutral path.
 
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