Impedance Voltage
Impedance Voltage
(OP)
Hi All,
we are adquiring two power transformers and the value of impedance voltage was specified as 12.25% +-10 but the value after the tests is 14.1%. the question is what are the implications, advantages or disavantages of having a value higher than specified.
thanks
best regards
Luis
we are adquiring two power transformers and the value of impedance voltage was specified as 12.25% +-10 but the value after the tests is 14.1%. the question is what are the implications, advantages or disavantages of having a value higher than specified.
thanks
best regards
Luis






RE: Impedance Voltage
The effect would be your losses are greater but the short circuit will be less due to the higher impedance.
If these are replacement transformers and the originals were 12.25%, you probably want to check the effect on the protection and on voltage drops.
RE: Impedance Voltage
Should you intend to run this transformer in parallel with some other existing transformer of similar rating, you may have to check the application again w.r.t load sharing and circulating current before accepting this transformer. If it is not to be paralleled with any existing trafo and the short circuit current increase is within the limit of the downstream equipment, you may penalise the vendor based on the increased losses and impedance and accept the transformer if it doesnot hurt you much (financially).
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RE: Impedance Voltage
ANSI standard tolerance for impedance is ±7% of the specified impedance, so you are already allowing more tolerance than standard. Tested values 15% higher than specified are a bit too much.
RE: Impedance Voltage
Mike
RE: Impedance Voltage
You're probably right. I wrote that from memory without looking it up. My memory ain't what it used to be.