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Three phase transformer

stefan-fan

New Member
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!
 

dr pepper

Well-Known Member
Most Helpful Member
Terminal designations can be confusing, and seem to change beetween countries.
Do you mean your trans has Uu, Vv, Ww, or some other designation.
3 phase trans can be connected in more than one way, but usually the rated voltages are affected, sometimes you can find out by the number of terminals, and yes by making a measurement.
Are you trying to run one on single phase?
 

stefan-fan

New Member
Terminal designations can be confusing, and seem to change beetween countries.
Do you mean your trans has Uu, Vv, Ww, or some other designation.
3 phase trans can be connected in more than one way, but usually the rated voltages are affected, sometimes you can find out by the number of terminals, and yes by making a measurement.
Are you trying to run one on single phase?
Thank you!

and 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... but how? ....


The upper star is primary sided, the bottom one secondary
Yy0_Uu_kl.jpg

/edit

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.
 
Last edited:

dr pepper

Well-Known Member
Most Helpful Member
Ltspice I think will do a 3 phase trans with 3 coils.
I think I have seen this before but I have to say I dont know the answer on this one.
Is there access to the star point?
 

stefan-fan

New Member
If I would exactly know, how this U-u bridge affects voltages and phases, I think the fact that the voltages U_Ww and U_Vv are identical would prove, that this has to be Yy0. This is, what I believe, the solution is.

Yes, in LTSpice, coils and K-directives make a transformer. Depending on the parameters (inductance[Henry], Coils inner resistances, source-voltages) the simulation behaves chaotically different, everytime I change something. So according to this, the U-u-bridges affects could be anything... I tried a lot around with this...

Theoretically there would be access to the star point but the task doesn't say anything about it so I don't think this matters. I was not supposed to measure there.
 

Grossel

Well-Known Member
What is the voltage ratio of the transformer?
 

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