Voltage Regulation for three phase Dzn Transformer

[Physicist3]

Hi,

I need to calculate the voltage regulation of the 3 ph Dzn transformer. I have knowledge of the current going into the primary winding of the transformer (Delta winding) and hence need to calculate the current in the secondary (load current) so that I can use this in the voltage regulation calculations. I am unsure of the current relationships for a Dzn transformer, are they the same as for a Delta - Star transformer (Dyn)? Also, for the voltage regulation, I have P.U. values of Positive Sequence Impedance Resistance and Reactance. Are these the values that I should convert into actual values and then use in the regulation equation, or do I use Zero sequence values as I have them also?

 

[jim hardy]

I am unsure of the current relationships for a Dzn transformer, are they the same as for a Delta - Star transformer (Dyn)?

I hope this helps..

This grabbed my curiosity because we had a zig-zag connected generator in our rod drive system.

This article shows how the windings are connected
http://electrical-engineering-portal.com/zigzag-transformer-connection-overview

i'd think a carefully made phasor diagram would answer your current relationship question
though I've never done that particular one.

 

[zoki85]

In zigzag winding connection, LV winding is split in two equal equal parts on two different legs.
This gives secondary phase voltage: V₂=2⋅V_z⋅cos 30° (see phasor diagram in Jim's post)

Also, for the voltage regulation, I have P.U. values of Positive Sequence Impedance Resistance and Reactance. Are these the values that I should convert into actual values and then use in the regulation equation, or do I use Zero sequence values as I have them also?

In a balanced 3 phase system you don't need zero sequence impedance.
Zero sequence component can appear only in the case of asymmetry, if the sum of currents in the phases is not 0.