Help me identify an unlabeled transformer

[TwinT]

Transformer

I have a transformer, but I don't know what KIND of tranformer is.

Nothing is written on it. Five terminals: 2 red, 2 blue, 1 gray(wider).
There's continuity between the two red's, and between the two blue's.

I don't know where it came from.

What I'm looking for is some kind of method (safe method) to measure its transform relation and how to connect it.

Thanks

PD: It's a big transformer(let's say the size of a 220VAC/30V 3A transformer)

 

[DarkJedi]

Re: Transformer

Most possible the gray cable is ground, the two red ones go to 220V and the other two are the output, +/- 15 V, connect it and meassure it with a multitester.

 

[flatulent]

Re: Transformer

Your safest bet is to use an audio oscillator set to a very low voltage to determine the turns ratio between different windings. This still will not tell you what frequency it works at and what mains voltage the primary is designed for. I would suggest that these last two uncertainties will cause a grave safety and fire issue which is more costly than your buying the right transformer for whatever you would have used this unknown one for.

 

[nicleo]

Transformer

If the AC main in your country follows UK standard, ie. 220VAC/50Hz, the rating of transformer should be 220VAC/50Hz too. Usually power transformer can be used for both 50Hz or 60Hz, but wrong AC main voltage (e.g. 110VAC transformer connected to 220VA main) will burn the transformer. flatulent's method of using signal generator (set at 50Hz) is a good approach to determine the transfromation ratio of the primary and secondary windings.

 

[IanP]

Re: Transformer

Her is how practically (safty issue is important!!!!!!!) determine what kind of transformer it is:

1. By measuring resistance (will be close to 0 Ohm) identify windigs

2. Use 10..25W 230V lamp (not fluorescent) in series with each winding.... voltage will devide between lamp and windig... according to the ratio you will be able to identify which windig is (if it is at all) the mains side (voltage should be devided almost 50-50), which is secondary and so on.
It is reasonably safe method and you will not burn anything...

 

[papyaki]

Re: Transformer

Hi,

Have a look there. It describe how to do some lab measurement to get transformer's parameter :

h**p://home.earthlink.net/~jimlux/hv/xfmrmeas.htm

replace * by t

 

[TwinT]

Eureka!

The transformer input are the red ones, the blue ones the output, and the gray terminal is ground(for what? if someone want to explain it), and the n = 3
(12VAC produces a 4VAC output).

Now, I would like to know the maximum current of the transformer(or its power)

Increasing level...

 

[IanP]

Re: Transformer

The "ground" one is usually the Faraday shield between primary and secondary windings...
To estimate power take different loads and measure voltage; if you find a load that will cause the output voltage to drop by, say, 10% that is your nominal load...
(as load you can use car 12V bulbs connected in series or in parallel...)