Transformer Phase Shift

[kingtutley]

I understand from IEEE that the high side of a 3p transformer whether delta or wye always leads the low side by 30 electrical deg. (IEEE standard apparently)

I have been told that it is possible to achieve a different angle from a transformer.

I assume this is done by hooking up the phases in a different way. for example(I hope my picture will look ok)
Imagine a normal configuration:
A || A
B || B
C || C

No suppose this:
A || C
B || A
C || B

What is happening here I cannot really understand mathematically. Is there an easy way to evaluate what the actual phase shift will be for a given configuration of transformer windings that might not be in a "normal" configuration?

I'm sure this question is as clear as mud.

 

[davidbeach]

I believe there is a paper at

http://www.basler.com

that goes into detail about this. For the transformer forget A, B, C and use H1, H2, H3 on the high side and X1, X2, X3 on the low side. Then, per ANSI standards H1 leads X1 by 30[°]. You can put any phase to any terminal (low side phases would generally be indicated as a, b, c rather than A, B, C so that high and low can be readily distinguished). Swap two phases on the high side and the same two phases on the low side and now low side leads the high side by 30[°]. Combine that with rotating phases and you can achieve any odd multiple of 30[°] desired.

 

[dpc]

This might help: faq238-1154

 

[JensenDrive]

The diagram you gave does not describe what is going inside the transformer delta windings. It does not show that the transformer converts phase to phase voltage on the delta side into phase to ground voltage on the wye side. Draw a set of Van, Vbn, and Vcn voltages for the primary voltages, and trace out the vectors associated with the following discussion:

Assume
H1-H2 transforms to X1-N
H2-H3 transforms to X2-N
H3-H1 transforms to X3-N
If you connect
A-H1, X1
B-H2, X2
C-H3, X3
You get
V A-B pri transforms to VAn sec
V B-C pri transforms to VBn sec
V C-A pri transforms to VCn sec
For this connection, VAn secondary leads Van primary by 30 degrees.

If you connnect
C-H1, X1
B-H2, X2
A-H3, X3
You get
V C-B pri transforms to VCn pri
V B-C pri transforms to VBn pri
V A-C pri transforms to VAn pri
Now VAn secondary lags VAn primary by 30 degrees.

Same xfmr, but how you connect the phases makes the difference. I believe some companies wish to always connnect phase A to H1 and X1, so they order xfmrs with different internal wiring instead of changing which phase connects to which bushing.

 

[JensenDrive]

Oops, I said in a line near the bottom:
V B-C pri transforms to VBn pri

This is a test: What was that supposed to be?

 

[waross]

Delta delta and wye wye do not normally phase shift.
The phase shift of multiples of 30 deg. is a characteristic of wye delta and delta wye connections.
There is a phase difference between the line to line voltages and the line to neutral voltages of a wye winding. The delta line to line voltages are in phase with the line to neutral voltages of the wye-delta and delta-wye banks.
If you look at the vector diagram on a transformer nameplate you will see that the line to neutral vectors on the wye side match the angles of the line to line vectors on the delta side.
respectfully

 

[mls1]

The other way you can get a 30 degree leading delta-wye transformer is by reversing the wye connections inside the transformer. Each phase is tied to a common point which becomes the neutral point in a four wire system. If you tie the other side to the neutral you reverse the phase voltage 180 degrees. If the standard configuration gave X1-A, X2=B, X3-C, the new configuration would give X1-B, X2-C, and X3-A with a 30 degree lead from the primary assuming you tie the same winding to the X bushings.

We ran into this recently when we brought in a new transformer with a standard 30 degree lag only to find the system was 30 leading. We used the method described by JensenDrive above to correct the 30 degree lead to 30 degree lag without changing the transformer internals.