three phase transformer

[Jk1996]

hi guys I'm trying to get my head clear on transformer winding polarity on a three phase transformer. what are the effects of one winding having an incorrect polarity wrt the other 2. I know the phase relationship will change but physically what will happen?

many thanks for your in-depth replies as per.

 

[davidbeach]

“Incorrect polarity” in what way? What winding configuration?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[davidbeach]

Also, is it a single 3-phase transformer or a bank of three 1-phase transformers? Much easier to get weird connections when you have access to both ends of each winding.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Jk1996]

Yes winding configuration?

 

[Palletjack]

Suggesting something like a DABY or DY11 and physically rearranging the coils?

Draw a delta…
Now take one vector and flip it 180 degrees. Figure your voltage from there.

 

[cranky108]

If it's a single three phase transformer, the nameplate should have the correct winding on it. But not always.
We had to get a new nameplate made several years ago, for a Y-Y 60 degree shift transformer. They changed the winding, and never remade the nameplate.

 

[prc]

As per IEC, all transformers will be with negative polarity (subtractive Polarity) for their windings. It means HV and LV will be wound in the same direction and voltage build-up will be in the same direction. Top H1, L1; bottom H2, L2. The advantage of this convention is the voltage between HV and LV will be less compared to positive polarity (additive polarity). As per C57.12.70 for small distribution transformers(less than 200 kVA) additive polarity is specified for the easiness in manufacturing.

 

[davidbeach]

A bit pedantic perhaps, but all wye-wye transformers have a 0 degree phase shift. Depending on what phase is connected to what bushing it is possible to get any of the even multiples of 30 degrees. 60 degrees requires a swap on each side, but not the same swap.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[cranky108]

david, I am struggling how you can get a 30 degree shift with a Y-Y. But that is not what this discussion is about.
My point is read the nameplate, but question it's accuracy from time to time. After all engravers only put what they are told.

 

[davidbeach]

“Even multiples of 30 degrees”, so 0, 60, 120, 180, …

I’ll see your silver lining and raise you two black clouds. - Protection Operations