# Transformer ratings given a nameplate

1. Jan 26, 2010

### vstrelok

1. The problem statement, all variables and given/known data
Essentially, there are 4 separate windings that are not connected. Two windings are on the top (H) and two are on the bottom (X). It is given that the rated power of the entire transformer is 5 KVA. The rated voltage is 120/240: 120/240. It also notes that the colon (:) in the rated voltage separates the primary voltages from the secondary voltages. The rated frequency is 60 Hz. H windings are primary, and X windings are secondary. In order to better see this, here is a picture.

So the questions ask:
1.) What is the rated voltage of a single "H" winding?
What is the rated voltage of a single "X" winding?
2.) What is the rated power of a single "H" winding?
What is the rated power of a single "X" winding?
3.) What is the rated current of a single "H" winding?
What is the rated current of a single "X" winding?

2. Relevant equations

None really.

3. The attempt at a solution

So I had difficulty understanding the voltage rating. I first thought that the top left winding had a voltage rating of 120 and the top right had 240. Or is it that each winding has a voltage rating of 120 volts, but if you combine the top two or bottom two you get the max of 240 volt rating? I am very confused. Any help would be appreciated!

2. Jan 26, 2010

### Staff: Mentor

Yes, you will need to connect the two half windings in series to get the 240V option part of the questions. You then have two options for how you make the 120V connection. Can you say what they are?

After you think about it some, you can see if this tutorial helps:

http://www.federalpacific.com/university/transbasics/chapter2.html [Broken]

I found it using a Google search on the following:

power transformer 120:240V input

Last edited by a moderator: May 4, 2017