Hi @Wfg42438,
The impedances Zps, Zst, and Zpt are obtained though a short-circuit test as you explained:
- Zps: Voltage applied on primary, secondary is shorted, tertiary is open. Therefore, Zps is the impedance between primary and secondary.
- Zst: Voltage applied on secondary, tertiary is...
Hi @electricuwe and all, after debate with manufacturer I find out the issue.
In order to deal with the additional heat coming from the harmonics, the transformer was oversized. The manufacturer then used the transformer oversized power to calculate the impedance at k=8. This approach was...
Hi Waross,
You are right, but in this case the impedance is specified to be on the AN mode (from right to left - second column is the project requirement, first column is the manufacturer answer).
I honestly don't understand this answer from the manufacturer. Constructively speaking, if the...
Thank you for the reply, @Gr8blu.
The change in the impedance from 7.5% to 6.6% is really impacting the fault levels downstream. Despite theoretically possible as you explained, when I look at the specification (6.6% @ K=1, 7.5% @ K=8), constructively speaking, I see two different transformers...
Hi everyone,
I have specified a transformer to have 7.5% impedance and k=8. I received a datasheet from the manufacturer with following information:
Transformer impedance - 6.6% @ K=1; 7.5% @ K=8
It is the first time I see a transformer impedance indexed to the k-rating factor. Have some of...
