transformer impedance

[paulimo]

If the impedance of a 100MVA single phase transformer is 6%. What is the 3-phase impedance of three identical 100MVA single phase transformers in a bank? The impedance will be at 300MVA.

 

[jghrist]

6%

Impedance of a three-phase bank is the impedance per phase.

 

[gar]

080727-1727 EST

There is no indication of whether this is a Y or delta.

Suppose it is a Y. Isolate one secondary and the impedance is the 6% specified. Now connect the neutral and still load that one secondary line to neutral, and the result is still the same.

Connect the secondaries in a delta with the same 6% impedance for that secondary. What is the source impedance seen by a single phase load across the secondary? It is less than 6%. You figure it out.

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