transformer for power supply?

[drescher3]

Hello all, I am starting a project...putting motors onto my manual router table. I am going to use a hobby cnc driver and someone gave me a transformer to use but I can't find any information on it and am wondering if it is going to work. I will post links to some pictures of it...or maybe put them here if I can figure out how to do that!

Thanks,

Dave
Oh yea, I am doing three motors probably under 200 oz.

[Al_The_Man]

First you need to find the primary winding, probably the two black wires, the winding should be the innermost one.
Do a continuity test to see which windings are connected or separate from each other.
Apply 120v to it and check the voltage on all the other windings.
The VA rating of the transformer is basically a result of total core size of the transformer and the current capability of the windings.
Al.

[drescher3]

Thanks for that. Is there a way to measure what the amps are on this transformer?

Dave

[Al_The_Man]

No definitive means, you can generally go by the physical size to get an idea of the VA.
Al.

[KOC62]

To further what Al said, the VA is also related to the temperature rise of the transformer. This has to do with the maximum internal core temperature.

One could arrive at a reasonable current rating based on the maximum core temperature, but this would assume one has the proper equipment and transformer knowledge to make a test setup.

[drescher3]

OK, I think I got my power supply up and running. This transformer actually had 5 secondary coils. the voltages were:
3.7
9.3
12.0
18.9
35.4

I went with the 18.9 and after running it through the capacitors, it came out to 25.1 Volts.

The store where I got my capacitors didn't have too much selection so I put two 4700 uF capacitors together. That was the largest they had...I feel like I should have gone with three though??

Here is a picture of what I set up:




Oh yea...one other question. I decided to try it out immediately so I hooked it up to my 24 volt computer cooling fan. It instantly fried it. Think that shows something wrong with my setup, or are their tolerances that tight...or maybe I shouldn't have had the two wires together...I have run that fan on 12 volts before?

I am afraid I know just enough electric to get me in trouble!

Dave

[Al_The_Man]

Computer fans are usually 12vdc, if ran off the PC P.S.?
Al.

[drescher3]

well, it said 24 vdc on it...so I thought one more volt wouldn't hurt it! I am not sure where it came from...

[KOC62]

I couldn't fully follow your transformer wiring.

From your photo I count 9 secondary wires (some hidden?);
2 blue, 2 grey, 2 red, 2 brown and one black, and two primary wires - black.

You list 7 secondary voltages.

Any of the wires a center tap?
Are all secondary wires the same wire gauge?
Any idea which equipment the transformer might have come from?

[drescher3]

Sorry about that...the 25.1 I had listed there was the final voltage...so I edited the post. Yes all the secondary wires are the same gauge. The black one formed a circuit with the orange ones...does that mean it is a center tap?

I believe it came out of a stereo system.

Dave D

[Al_The_Man]

The black one formed a circuit with the orange ones...does that mean it is a center tap?
Dave D

Measure the AC between the ones that have continuity and you can tell the centre taps from this.
Al.

[drescher3]

It was very late when I posted the transformer voltages I went back and edited them to be right! Here are the values before and after the rectifier and capacitors:

Grey-grey 3.7 4.4
orange-black 9.3 12.0
red-red 12.1 15.9
orange-orange 18.9 25.1
blue-blue 35.4 47.4

Dave D