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transformer symbols

transformer symbols

transformer symbols

(OP)
Hi everyone

My knowledge of electrical stuff is not the best.
Can someone explain the meaning of the following symbols used on three phase transformers, and how do you determine it:  
  
                       : Z%
                       : Z0%
                       : X/R ratio

I've seen on the nameplates of some transformers just the MVA, the voltages and currents(pri. and sec.), the impedance (X%), type of cooling and the vector symbols.

Thanks

RE: transformer symbols

z% = transformer impedance

z0% = transformer zero sequence impedance

x/r ratio = the ratio of reactive and resistive components of the transformer


Mike

RE: transformer symbols

(OP)
Thanks Mike

1.So z% is the same thing as x% ?
2.How do you calculate z0% and the X/R Ratio? - I haven't see it on any transformer nameplate.

RE: transformer symbols

Z% is the impedance, comprising both the resistance (R%) and reactance (X%).  Think of the resistance and the reactance as vectors 90 degrees apart.  The impedance is the vector sum of the two, so Z^2= R^2 + X^2.  What you normally see on the nameplate is Z%.  R% can be calculated by dividing the full-load loss by the rating and multiplying by 100.

Z0% is equal to Z% for two-winding transformers with solidly grounded neutrals.  Except as seen from the delta side of a delta-wye transformer, Z0% is infinite.  For three-winding transformers, you need tests of the individual winding impedances.

The X/R ratio is X% divided by R%.  If you have Z% and calculate R% as above, you can calculate X% by solving the above equation for X.

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