Step up Transformer?

[JFletcher]

What would you use 480V on that only would be supplied by two legs?

480V lighting.

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The model #, job# and serial# of the xfmr is the same in both pics; they are of the same unit.

~~~~~~~~~~~~~~~~~

This link:

http://federalpacific.com/training/transformer-basics/chapter-2.htm

may help as might this one:

https://stevenengineering.com/tech_support/PDFs/55MAIN.pdf

which says an xfmr this size can be reverse fed.

winnie, where is the high side center tap? I dont see it and the schematic appears to show one primary/high side coil and two secondaries/low side the latter of which can be wired series or parallel.

like infinity I'm just not seeing how one could get 240 and 480 simultaneously from the high side

 

[mwm1752]

To sum it all up, if you are stepping up with that transformer there should not be anything connected to the X2,X3 and you are going to end up with straight 480V on the high side, no chance of getting 480/240.

What is the application?

The description related in my OP is from the EC.

The application is for a 277/480 3 phase water pump to remove water from a construction dig. The GC wants to serve this transformer with 120/240 & send out a 2 phase 480v feeder. The contractor also wants to set up an auto transfer switch so that a 277/480 3 phase generator can also power this pump -- They also want to set up a converter to take the 2 phases of the 480v & convert to 3 phase 480V in order to run this pump -- I just see lots of red flags in this unusual set up - OCP for load side of connection (terminate in OCPD) is there a grounded conductor (originating at the transformer ) electrodes (required at 480v 1st point of disconnect)

So this is for a temp service - should my authority stop after the 120/240v temp service equipment feeding this transformer even though I have doubts about the wiring terminations?

 

[mwm1752]

480V lighting.

~~~~~~~~~~~~~~~~~

The model #, job# and serial# of the xfmr is the same in both pics; they are of the same unit.

~~~~~~~~~~~~~~~~~

This link:

http://federalpacific.com/training/transformer-basics/chapter-2.htm

may help as might this one:

https://stevenengineering.com/tech_support/PDFs/55MAIN.pdf

which says an xfmr this size can be reverse fed.

winnie, where is the high side center tap? I dont see it and the schematic appears to show one primary/high side coil and two secondaries/low side the latter of which can be wired series or parallel.

like infinity I'm just not seeing how one could get 240 and 480 simultaneously from the high side

Thanks JFLETCHERwill read carefully

 

[jap]

What would you use 480V on that only would be supplied by two legs? your not going to get 3phase out of a single phase XFMR.

Any 480v Single Phase Load.

Lighting, Transformer Primaries, Heat Blankets, ETC......

JAP>

 

[mwm1752]

A bit more info the phase converter they want to use is VFD which is possible just sizing will be a concern -- there is no XO for the grounded conductor so in the pic I would think if it was energized a big boom might happen. The info on the transformer confirmed primary is 480v & secondary 120/240v - I can't find any documentation that this can be reversed to be a step up type application.

 

[ActionDave]

The description related in my OP is from the EC.

The application is for a 277/480 3 phase water pump to remove water from a construction dig. The GC wants to serve this transformer with 120/240 & send out a 2 phase 480v feeder. The contractor also wants to set up an auto transfer switch so that a 277/480 3 phase generator can also power this pump -- They also want to set up a converter to take the 2 phases of the 480v & convert to 3 phase 480V in order to run this pump -- I just see lots of red flags in this unusual set up - OCP for load side of connection (terminate in OCPD) is there a grounded conductor (originating at the transformer ) electrodes (required at 480v 1st point of disconnect)

So this is for a temp service - should my authority stop after the 120/240v temp service equipment feeding this transformer even though I have doubts about the wiring terminations?

These sound like some oil field guys I know. Whoever hooked up that transformer ran a neutral to the "primary side" and that makes me think that these guys are a tad bit over their heads. If they blow up the VFD of fry the motor that's on them

Since the transformer is labeled Hi and Low it is probably suitable to be reverse fed.

Feeding a roto phase with 480V single phase to feed a three phase pump is very common where three phase power is not available, so nothing unusual there. Using a VFD as a phase converter is also common but the it has to be a VFD that is made to allow that application. It's just all the little details that need ironed out, is it the right kind of equipment properly sized is the first one.

 

[mwm1752]

Dave,
The specs found on the manufacture website does indicate primary & secondary volts & UL white book requires markings to be on product. Does that additional info have any impact on whether the transformer can be reverse fed -- again appreciate comments. No oil fields around here.

 

[jap]

Other than not being able to see the Neutral bond in the post 1 picture, it looks to be correct for a "Step Down" Transformer 480v primary 120/240v secondary.
If this is wired for a "Step Up" Transformer from 240v input to a 480v output and hasn't been energized yet, I wouldn't take that next step.


JAP>

 

[iwire]

Dave,
The specs found on the manufacture website does indicate primary & secondary volts & UL white book requires markings to be on product. Does that additional info have any impact on whether the transformer can be reverse fed -- again appreciate comments. No oil fields around here.

The transformer label posted in the OP does not indicate primary or secondary it only indicates high voltage / low voltage.

In my opinion this is deliberate so the transformer can be used in either direction.

 

[winnie]

winnie, where is the high side center tap? I dont see it and the schematic appears to show one primary/high side coil and two secondaries/low side the latter of which can be wired series or parallel.

like infinity I'm just not seeing how one could get 240 and 480 simultaneously from the high side

From what I can see there is not a 'proper' high side center tap terminal. (No 'H0' on the terminal bar.)

However the voltage changing taps are clearly at the voltage center point of the high side coils. The nameplate clearly indicates that the voltage you can connect H1 and H2 to the taps on the opposite coils to get a 240V output. So it is entirely plausible to me that in the 480V configuration, if there were a suitable way to connect to the voltage changing tap jumper, that you would have a high side center tap. The thing missing is a defined 'proper' way to make this connection.

-Jon

 

[ActionDave]

The transformer label posted in the OP does not indicate primary or secondary it only indicates high voltage / low voltage.

In my opinion this is deliberate so the transformer can be used in either direction.

I agree.

Added... I agree the transformer is suitable for reverse feed, I'm not sure there is an option for a center tap on the high side like Winnie was talking about.

 

[mwm1752]

Talked to a Jefferson tech & this is what he described as wiring -- Not sure about 4# but please comment

 

[augie47]

Talked to a Jefferson tech & this is what he described as wiring -- Not sure about 4# but please comment

connecting 3 to 4 completes the HV winding to give you 480v based on your 240v input.
If you need to adjust then output you can change the jumper based on the Table
(1 to 2 gives you 504v, 3 to 2 =492, etc.). If you 240 is + or - you cna change these taps to give you the desired output.

 

[mwm1752]

connecting 3 to 4 completes the HV winding to give you 480v based on your 240v input.
If you need to adjust then output you can change the jumper based on the Table
(1 to 2 gives you 504v, 3 to 2 =492, etc.). If you 240 is + or - you cna change these taps to give you the desired output.

yes per the transformer spec - Does schematic 4# secondary with a center tap for the grounded conductor look applicable to get 2- 240v phases?

 

[winnie]

yes per the transformer spec - Does schematic 4# secondary with a center tap for the grounded conductor look applicable to get 2- 240v phases?

Schematic #4 will give you 240V to 240/480V step up.

If Jefferson 'blesses' making output connections to the taps on the transformer winding, then I can't see a problem with it. You probably need to give consideration to the exact sort of wire used to connect to the taps and possibly using high temperature wire/splices.

Just to be clear, you will have 2 240V legs of a single phase 480V supply, not 2 separate phases.

-Jon

 

[ActionDave]

yes per the transformer spec - Does schematic 4# secondary with a center tap for the grounded conductor look applicable to get 2- 240v phases?

Yes. Good to go I would say.

 

[ActionDave]

Schematic #4 will give you 240V to 240/480V step up.

If Jefferson 'blesses' making output connections to the taps on the transformer winding, then I can't see a problem with it. You probably need to give consideration to the exact sort of wire used to connect to the taps and possibly using high temperature wire/splices.

Good catch figuring that one out from the photo.

Just to be clear, you will have 2 240V legs of a single phase 480V supply, not 2 separate phases.

-Jon

That is not going to matter to anyone out there hooking it up.

 

[ggunn]

They also want to set up a converter to take the 2 phases of the 480v & convert to 3 phase 480V in order to run this pump...

How, exactly, would they do this? AFAIK you cannot convert 480/240V single phase into 480/277V three phase with just transformers.

 

[iwire]

How, exactly, would they do this? AFAIK you cannot convert 480V single phase into 480/277V three phase with just transformers.

Pretty sure he means with a phase converter.

 

[JFletcher]

From what I can see there is not a 'proper' high side center tap terminal. (No 'H0' on the terminal bar.)

However the voltage changing taps are clearly at the voltage center point of the high side coils. The nameplate clearly indicates that the voltage you can connect H1 and H2 to the taps on the opposite coils to get a 240V output. So it is entirely plausible to me that in the 480V configuration, if there were a suitable way to connect to the voltage changing tap jumper, that you would have a high side center tap. The thing missing is a defined 'proper' way to make this connection.

-Jon

Thank you for the explanation. I didnt see that the taps were at the midpoint. I suppose an insulated Polaris "T" tap would get the job done tho the tap lugs on the xfmr may not be suitable for larger wire and tapping the existing paralleled jumpers goes from mfg eqpt to field wiring and istm would violate 310.4.