Transformer impedance

[jordan__94]

Hi, i need some help guys.
I have to simulate a transformer (DYn1) and i need as parameters the Zequal of winding 1, the Zequal of winding 2 and magnetization resistance and reactance. I have computed the R1,X1 for positive sequence(so negative) and R0,X0 for zero sequence, from known data. So the question is, how can i extract the data i need from Z1,Z0 that already known?

 

[dpc]

For the resistance, you can calculate this if you know the transformer losses or the actual X/R ratio. Or assume a typical X/R ratio per IEEE Red Book. The %Z should be on the nameplate or datasheet.

http://www.publicpower.org/Media/magazine/ArticleDetail.cfm?ItemNumber=17451

 

[jordan__94]

I have as known data, the ratio of zero-sequence X0/RO, the Ploss of core,the short-circuit applied voltage for positive and zero sequence (Uk1 and Uk0) for a transformer 50 MVA, 150/20 kV. So i found, Z1 and Z0 for positive and zero-sequence, but the simulation program, asks me for Z1 and Z2 of windings 1 and 2. So what's the connection between my known data (positive and zero sequence impedance) and the asking data (impedance of winding 1 and 2)?

 

[jordan__94]

No one? Any idea?

 

[magoo2]

I would assume the winding impedance is half of the Z1 or Z2 for a 2-winding transformer.

 

[prc]

For a two winding transformers, it is not possible to allocate the reactance or impedance between two windings to individual windings. This is like allocating distance between two points A and B to individual destinations. But it is possible to do it for three winding transformers. Pioneers thought about it and discussed. See A.Boyajian " Resolution of transformer reactance in to primary and secondary reactances. AIEE Journal June,1925,Page 805

 

[waross]

I am not sure about this so I pose it as a point for discussion:
The inductive reactance of a coil is proportional to the square of the number of turns.
The primary and secondary are wound on a common core.
Will the ratio of the reactances be in the ratio of the square of the turns ratio?
So, will the reactances of a 480 Volt to 240 Volt transformer be 4:1 or 80% for the primary and 20% for the secondary.

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

 

[prc]

waross, what you are considering is self inductances. As we are discussing is the mutual inductance (or leakage reactance) between two windings and hence it becomes indeterminant.

 

[waross]

Thanks prc.

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