Transformer Wiring Diagram 3

[rockman7892]

I am trying to find a wiring diagram for a particular European (German manufacturer) transformer but have had no luck searching online. I am trying to determine how the connections are made on this transformer and the voltage readings I'm getting are strange and are not lending any clues. I am therefore after a wiring diagram to see how its connections are made. The transformer has the following information:

Jacke Transformatoren Gmbh
Einphasen-Transformator nach UDE 0550/0570
Art.Nr.-EAM53,2460230
Ser Nr:2014159V820 2
Typ: EAMS 3,2 KVA
PRI: 460V +/- 7.3A
SEC: 230V 13,9A
Lio IP00 60/60Hz T40/B

Does anyone know where I can find a wiring diagram for such a transformer? It has two transformers windings and cores connected in parallel but I cannot seem to figure out exacty how they are wired.

 

[bogeyman]

If there are only 2 cores (your post isn't too clear) this may be scott tranformer which can used to convert 3 phase to single phase while loading all three phases equaly, google it or try wiki.

 

[rockman7892]

bogeyman

The two transformer cores were fed from the same (2) legs only of a 3-phase source. The two legs came into a terminal block and from the terminal block two wires each were paralleld out to each core and winding set. The secondary of the two cores were also then paralleled back to the a single two wire terminal block. It almost appears that the two cores are in parallel to give a total of 3.2kVA.

The thing that is throwing me off is that the votlage readings on the secondary when the wires are isolated are all over the place and its hard to even describe or troubleshoot without a schematic. This transformer when in operation is a 230V L-N transformer. I am wanting to try to maybe split the secondary coils to derive a 115 leg with a neutral on each side but I cant figure out how it is wired.

 

[ScottyUK]

Two cores in parallel? Can you post a photo of this transformer - sounds like a strange beast.


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If we learn from our mistakes I'm getting a great education!

 

[burnt2x]

My little German:
[ol] 1. Eine - one; Phasen - phase. Einphasen is therefore "single-phase"[/ol]
[ol] 2. Transformator nach VDE 0550/0570 - Transformer according to VDE 0550/0570 (VDE -"Verband Deutscher Elektrotechniker", German Association for Electrical, Electronic and Information Technologies)[/ol]
I tried Google and found out Jacke Transformatoren was bought out by Schaffner of Switzerland.

 

[edison123]

It sounds a like plain vanilla single phase trafo to me. Could you post some photos here ?

 

[waross]

Actually I was under the impression that a Scott connection did not provide a perfect balance on three phases. I may be wrong, but when I compare a Scott connection with a "T" connection that transforms three phase to three phase and does give a balanced loading on three phases if the load is balanced, I doubt it.
Everybody talks about the Scott connectionbut almost no-one has ever seen one.
What is similar to but not interchangeable with the Scott connection is the "T" connection. This was at one time very popular for transforming 480 V three phase to 120/208 V three phase. A common configuration was 25 KVA dry type.
Also using two cores are open delta auto-transformers common in Canada for running 480 V motors from a 600 V source.
And of course there is the old standby the open delta circuit with two cores (or two transformers).
But Scott connections (which convert between three phase and two phase): Except for a couple of small dedicated legacy installations, not for many decades.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rockman7892]

I will be able to post a picture of this transformer. Hopefully it will help clear things up

 

[rockman7892]

The following are pictures of the unit

 

[rockman7892]

Here is another

 

[rockman7892]

One more

 

[edison123]

Looks to me a standard single phase trafo with taps on the primary.

 

[ScottyUK]

Man, those are bad photographs! Does your camera have a focus feature? The nameplate night contain some useful information if we could read it. If the nameplate is really reflective take the photograph at a slight angle to avoid direct reflection of the flash back at the camera.

I concur with Edison, it looks like a dual primary, dual secondary transformer with multiple taps.


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If we learn from our mistakes I'm getting a great education!

 

[rockman7892]

Sorry about the poor quality photos the camera is kind of poor.

The nameplate info has is everything that I contained in my origonal post.

So with a dual pri dual second transformer I guess the two sets of windings are in parallel? Why put two windings in parallel just to increase the capacity of the unit for non standard sizes?

Like I said this unit was a 230v L-G unit however I could not find where one of the legs was grounded. I was trying to put the secondary coils in serirs and ground the center to have two 115 L-G voltages. The unit may have not been grounded and could explain my strange readings.

 

[edison123]

3.2 KVA is too small for parallel windings, but then we really don't know what the OEM did.

I would suggest that you backfeed from 230 V and measure the voltages across all the taps on the 460 V.

 

[ScottyUK]

With a dual primaries and dual secondaries you have four possible connection permutations, excluding taps: series primaries with secondary in parallel or series, and parallel primaries with seco0ndary in parallel or series. Quite a flexible design.


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If we learn from our mistakes I'm getting a great education!

 

[waross]

It is common in North America to construct dual winding transformers in small sizes for the reasons Skotty pointed out. Also spreading the windings on both legs of the core may reduce leakage flux.
Rockman, often if you want a ground on a new transformer you have to install it. If you have been measuring voltages to ground on an ungrounded transformer you will get strange readings.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rockman7892]

So essentially if each winding set had a 480-240 or 2:1 ratio than I could essentially create an isolation transformer by connecting the primary two windings in parallel and the secondary two windings in series? This would give me 480V across the primary windings, and then 480V across the series combinatin of the secdondary windings. Is this correct?

Does polarity matter when making these winding connections?

 

[ScottyUK]

Yeah, in principle you could do that.

Yes, polarity does matter: if you connect them in anitphase then you will get 480V. If you connect them in phase you will get 0V or at least very close to zero.


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If we learn from our mistakes I'm getting a great education!

 

[rockman7892]

O.K. so for any combination I could measure seperately across each set of secondary dual windings (not connected to anything) and read the expected voltage across each winding depending on how the primary windings were configured. It would then depend no the polarity of these secondary windings for how I connected them together in either series or parallel to get the correct output voltage.

Is there an easy way to determine the polarity of these windings without having a schematic? If the windings are oriented the same way physically on the secondary will they be the same polarity or is it determined on how the primary is connected?

I think the problem with my strange voltage readings before was due to the fact that all of the secondary windings were disconnected and I was trying to read each one of these windings to ground and thefore getting strange readings based soley on a capacitive coupling to ground and not a solid ground anywhere. I think maybe the origonal configuration was not grounded. I assumed since it was a 230V L-G unit it would be grounded on the one side of the secondary windings but I did not see this ground connection anywhere. I was hesitant to then split the secondary windings and ground the center tap if there was already a ground somwhere I could not see. The easy thing may have been to use a meter to check a resistance to ground.

Also If I wanted a 120/240 secondary I would have to put both the primary and secondary sets of winddings in series for a 480V primary source.