# Three phase transformer

#### stefan-fan

Joined Dec 3, 2019
2
Hi,

if U-u of an Yy0-transformer (e.g.) is connected, does this affect voltage-values and/or phases? If so, how? I'm asking because somehow by connecting U-u and measure U_Ww and U_Vv it is possible to find out, how the transformer is connected -as Yy0 or Dy5 or Yz11...... and I have to find out how this is done. This technique just doesn't seem to be explained anywhere...

Do you maybe know what I'm talking about?

Thank you!

Joined Jul 18, 2013
28,825
Not clear what your intentions are!
Two transformers? Or dual winding?
Max.

#### stefan-fan

Joined Dec 3, 2019
2
Not clear what your intentions are!
Two transformers? Or dual winding?
Max.
Sorry, I should have explained the situation a bit clearer...

It's a task of the energy systems course. I have to prove that it is connected as Yy0 by connecting U and u and measuring the voltages between W and w and between V and v (U_Ww and U_Vv). I measured 3,3V each. Without the U-u-connection they are zero and in the vector diagramm U and u have to stay at the same spot because of this connection. So somehow, voltages or/and phases have to change. And somehow it is possible to prove this way, that this is Yy0...

I don't have a transformer at home and I couldn't reproduce this as a simulation Qucs or LTSpice. So I can't just measure all the voltages and phases when U and u are connected.