how percentage impedence effect on the size of the power transformer?

how percentage impedence effect on the size of the power
transformer?

Question Posted / jraj

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how percentage impedence effect on the size of the power transformer?..

Answer / jaswinder

% impedence is use to determine the max fault current the
transformer is capable of delivering to a downstream short
circuit.
Fault current=FLC*100/%imp.
this fault current is use to cal fault MVA
Fault MVA = 1.732 x fault current x V.

eg: If transformer of 2000kVA,5%imp having flc of around
1200A is use to supply to a motor of same flc carrying
capacity and if the voltage drop at transformer terminal is
more than the permissible voltage drop (+- 10%)during
stating of motor then the above transformer will be of
lower rating hence we have to select the transformer rating
higher than 2000kVA eg:-3000kVA (In other words transformer
having higher SC current capability ).If voltage remain
within the rated voltage of the motor then no oversizing of
tranformer is required.

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how percentage impedence effect on the size of the power transformer?..

Answer / akr

hieght of winding effect on impedane

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