Step up Transformer with optional secondary

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dmagilbertelectric

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A customer has a transformer that is fed from a 1200 amp soft start. The xfmr is 480v primary and the secondary can be switch from wye to delta. Wye gives a 4160v load and delta a 2400v load. In delta i have jumpers from H2-H3 and H4-H5. With my load landed on H2,H4,and H6. I personally have never encountered such a situation and im just curious if this sounds accurate.

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dmagilbertelectric said:
A customer has a transformer that is fed from a 1200 amp soft start. The xfmr is 480v primary and the secondary can be switch from wye to delta. Wye gives a 4160v load and delta a 2400v load. In delta i have jumpers from H2-H3 and H4-H5. With my load landed on H2,H4,and H6. I personally have never encountered such a situation and im just curious if this sounds accurate.

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Click to expand...

Re-connectable wye-delta transformers are not uncommon. What are all of the connections as shown on the nameplate?
You did not mention any jumpers for either H1 or H6
 
This is what they have
03399a8bef153618b7c4e33a1fc7151d.jpg
deef5302eb133fcae80133b0b73ddf5d.jpg


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dmagilbertelectric said:
This is what they have
Click to expand...

The windings appear to be between H1->H2, H3->H4, and H5->H6.

It seems to be connected in a wye.
It looks like there is a jumper from H1-H3 and from H3-H5.
The load conductors are on H2, H4, and H6

For a delta connection the jumpers would probably be H2-H3, H4-H5, and H6-H1

The nameplate says the wiring diagram is inside the cover.
 
jim dungar said:
The windings appear to be between H1->H2, H3->H4, and H5->H6.

It seems to be connected in a wye.
It looks like there is a jumper from H1-H3 and from H3-H5.
The load conductors are on H2, H4, and H6

For a delta connection the jumpers would probably be H2-H3, H4-H5, and H6-H1
Click to expand...
Ya sorry that is an older picture from when it was in a wye. When u came back to this job they said they moved it to delta for 2500v. So are they missing a jumper or will it work the way it is? I was just hired for the med voltage terms.
76ba7b99e4b4c37b33433a9400626694.jpg


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jim dungar said:
The windings appear to be between H1->H2, H3->H4, and H5->H6.

It seems to be connected in a wye.
It looks like there is a jumper from H1-H3 and from H3-H5.
The load conductors are on H2, H4, and H6

For a delta connection the jumpers would probably be H2-H3, H4-H5, and H6-H1

The nameplate says the wiring diagram is inside the cover.
Click to expand...
The way it is now, if im not mistaken, its in an open delta configuration on the load side

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dmagilbertelectric said:
The way it is now, if im not mistaken, its in an open delta configuration on the load side

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Click to expand...
I would not typically use an open delta configuration with windings on a common core.

I would think they should have a jumper from H6-H1, but then I haven't seen the wiring diagram, which should be inside the cover.
 
jim dungar said:
I would not typically use an open delta configuration with windings on a common core.

I would think they should have a jumper from H6-H1, but then I haven't seen the wiring diagram, which should be inside the cover.
Click to expand...
Ya thats what i said.. i mean it works in an open delta but i said i would jumper H1-H6

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