turn ratio 13.800kv to 138.000 step up transformer

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rosie06

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can any one tell me the turn ratio of a 13.800kv primary to 138.000kv secondary 3 phase step-up transformer.
 

n1ist

Senior Member
Location
Massachusetts
Occupation
Principal Electrical Engineer
It's a regional thing. Some countries use periods as the divider between groups of 3 digits, while others use commas.

/mike
 

beanland

Senior Member
Location
Vancouver, WA
Voltage

Voltage

Wye-Delta, Wye-wye, delta-delta, polygon, zig-zag, none matters because standard practice is always line-line voltage.
 

hurk27

Senior Member
It's a regional thing. Some countries use periods as the divider between groups of 3 digits, while others use commas.

/mike

I simply went from the OP as he did include the "k" in the "kv" so assuming that the transformer was not meant as a 138 meg volt transformer the dot would be correct indicating a 13.8 kv to 138 kv transformer which would be a 1 to 10 ratio.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Wye-Delta, Wye-wye, delta-delta, polygon, zig-zag, none matters because standard practice is always line-line voltage.

It does matter. With a delta to wye, a 1 to 10 ratio with 13.8 KV L-L input voltage would produce a 138 KV L-N output voltage. That would be 239 KV L-L on the output.
 

beanland

Senior Member
Location
Vancouver, WA
Coil Turns Ratio versus Transformer Ratio

Coil Turns Ratio versus Transformer Ratio

Well taken. If you deal with the coil turns ratio, then knowing the type of winding is critical. If you want the transformation ratio, since the standard is line-line voltage, the coil configuration does not matter.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110808-1035 EDT

I do not know what is standard practice on high voltage transformers, but on many low voltage units the more likely ratio is about 1 to 10.3 or 11 to account for near full load voltage drop. If voltage drop is handled by a voltage regulator, then 1 to 10 could be used.

.
 

beanland

Senior Member
Location
Vancouver, WA
Small vs Large

Small vs Large

Very good point. The X/R ratio of large power transformers is in the 20-50:1 range. In small power transformers it may be 5:1 or less. Large power transformers have voltage regulators or on-load tap changers to regulate voltage. So, it makes sense for a step-down transformer needing a 10:1 ratio at full load to actually have a 9.5:1 turns ratio. The voltage will run a little high at no load but will be better at full load.
 
It's a regional thing. Some countries use periods as the divider between groups of 3 digits, while others use commas.

/mike

...and this forum is about the NEC which is the US - as are most participants - so we barely tolerate our friends 'English' form accross the pond, nevermind the singular application of numerical forms.:lol: never you mind the fact that it was used in a contradictory fashion even in the origianl post, placing three meaningless decimal '0'-s after the whole numbers instead of 2, which is the same in ALL countries.
 
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jdsmith

Senior Member
Location
Ohio
Coil Turns Ratio versus Transformer Ratio
Well taken. If you deal with the coil turns ratio, then knowing the type of winding is critical. If you want the transformation ratio, since the standard is line-line voltage, the coil configuration does not matter.

This is a big deal - maybe a lot of folks think in terms of transformation ratio, which is pretty trivial - just divide, multiply, whatever. If I hear 'turns ratio' I'm probably interested in a higher level of detail than just transformation ratio - I might be reading a test report or evaluating a transformer bid or something where the coil turns ratio matters, and so the coil connections (delta vs. wye) also matter.
 
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