# Transformer analysis

Discussion in 'Homework Help' started by matt11111, May 22, 2009.

1. ### matt11111 Thread Starter Member

May 12, 2009
11
0
I am trying to model a transformer in an analysis software called ETAP. The software requires various information to model the TX such as primary, secondary, and tertiary rated KV,KVA,Max KVA. It also requires values for % impedance and X/R ratio between P and S, P and T, and S and T.
I have contacted the manufacturer and they have told me the TX is so old they have no information on it.

Is there anyway to measure the required information?

Nov 9, 2007
5,005
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3. ### PRS Well-Known Member

Aug 24, 2008
989
35
The way to get the R (winding resistance) parameter is to use an ohm meter. Do this between all windings.

To get the X parameter you can put a big (1000 uF or more) capacitor in parallel with the primary to create a tank circuit. Now sweep the frequency (you need a function generator or some other variable signal source) and when the sinewave peaks you have the resonant frequency.

Solve this for L: f=1/(2*pi*sqrt(L*C))

Then to find X at 60 Hz, X = 2*pi*60*L

Do this for the secondary and the center tap, too.

Your KVA max comes from the max voltage times the max amperage. Amperage is determined by wire size. Check out the NEC for the table on wire size vs safe maximum current. You define the voltage the xformer will work at. The product is your KVA rating.