Voltage Regulation for three phase Dzn Transformer

• Physicist3

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?

Answers and Replies

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.

In zigzag winding connection, LV winding is split in two equal equal parts on two different legs.
This gives secondary phase voltage: V2=2⋅Vz⋅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.