A question....Transformer ratio ( sqrt (3)/2 ) problem. 1

[rayas91]

Hello friends,

I have a question...Omicron cpc100 manual says that if you want to test of transformer ratio , you should use following calculationames.

Ratio = ( Vpri / Vsec ) * sqrt (3)/2


But I couldn't understand "sqrt (3)/2" where comes from ?

 

[waross]

That may be for a delta:wye transformer.
To keep it simple consider a Delta:Wye, 480V to 480V isolation transformer. The transformer voltage ratio is 1:1, the secondary winding voltages are 277V
This is a winding ratio of 1:1/sqrt (3) or 11/1.73)
I don't know where the last "2" in the equation comes from unless it refers to footnote #2. Hard to say without some context.
For a delta:delta or for a wye:wye transformer there will be no sqrt (3) term.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rayas91]

Thanks for ur answer..I know about sqrt3 but..."2" I dont know why we use it...

 

[waross]

I tried to look at the manual on-line. On one site the manual was was for sale, a couple of other sites claimed to offer the manual but I did not trust the sites so no joy.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[111R]

See attached image. This occurs on wye windings with no access to the neutral during testing. The low side has two windings in series which doubles the turns.

 

[rayas91]

Waross and 111R thank you for your interrest.

I understand that constant( sqrt(3)/2 ) with your help...many many THANKS.


sorry for my english.

 

[waross]

My thanks also, 111R.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter