# Center Tap Xformer Question

Discussion in 'General Electronics Chat' started by slfowler1, Apr 12, 2011.

1. ### slfowler1 Thread Starter New Member

Mar 2, 2011
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Just a simple question concerning center tap transformers and current, to see if I understand it correctly. I've read the e-book, but I'm still not 100% clear.

Let's say I have a 48VA 24VCT transformer. If the secondary is wired to produce 24 volts then it could produce 2A of current (ignoring de-rating for simplicity sake).

Now, if you wire from one end of the secondary to the center tap, producing 12 volts, would you be able to draw a (theoretical) 4A of current from it?

And then if all three taps are wired to make a +/-12V dual power supply, can each "side" of the supply only draw up to 1A?

Thanks for your help!

- Steve

2. ### bertus Administrator

Apr 5, 2008
18,682
3,633
Hello,

If the windings of the transformer are seperate, they can be put in series for double voltage or parallel for double current.
You MUST take care of the start and end of the windings.
Take a look at the attached PDF from ILP.

Bertus

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3. ### slfowler1 Thread Starter New Member

Mar 2, 2011
3
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Thanks -- I can see that parallel-ing two separate secondaries can double current. What I'm unclear about is what the effect on available current is by using only half of one secondary (i.e. from end to center tap). Is the current the same as that of the entire secondary (at half the voltage), or is the current halved? or doubled?

4. ### bertus Administrator

Apr 5, 2008
18,682
3,633
Hello,

The TOTAL power is 48 VA.
If you use only one part of the windings, the current will be the same at half the voltage.
(so half the power is used).
The wire thickness of the winding determents the maximum current.

Bertus

5. ### slfowler1 Thread Starter New Member

Mar 2, 2011
3
0
Thank you so much!

- Steve