Transformer Nameplate
Transformer Nameplate
(OP)
Hello Everyone,
I came across this transformer nameplate which shows 4 impedance values. My interpretation is a combination of voltage and mVA has a corresponding %Z. Has anyone seen this before and have any idea why four impedances?
I came across this transformer nameplate which shows 4 impedance values. My interpretation is a combination of voltage and mVA has a corresponding %Z. Has anyone seen this before and have any idea why four impedances?






RE: Transformer Nameplate
RE: Transformer Nameplate
10 MVA / 69 kV-34.5 kV: pos = 5.04%, zero = 5.04%
12.5 MVA / 69 kV-34.5 kV: pos = 6.31%, zero = 6.30%
20 MVA / 69 kV-12.47 kV: pos = 9.71%, zero = 9.86%
25 MVA / 69 kV-12.47 kV: pos = 12.28%, zero = 12.32%
The 34.5 kV impedance is almost half that of the 12.47 kV impedance because of the change in base.
The 12.47 kV winding is made up of three equal winding sections that are connected in parallel. These same winding sections are connected in series to give 37.41 kV. A small section of one of the winding sections is left out of the circuit so that you get 34.5 kV rather than 37.41 kV as the nominal voltage. This small missing section is why the 34.5 kV impedance is not quite half of the 12.47 kV impedance.
RE: Transformer Nameplate
RE: Transformer Nameplate
RE: Transformer Nameplate
RE: Transformer Nameplate
RE: Transformer Nameplate
RE: Transformer Nameplate