EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Jojo_France on October 31, 2024, 08:32:19 am
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Hello.
I've found some old Orega transformers, but I can't identify the exact model. I can't find any information on the net.
Can you help me? Here is the picture.
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Unfortunately, the majority of transformers that you find in equipment and on the surplus market are customs. They were wound to spec and were left overs. Getting transformers custom wound is one of the cheapest customs you can do as a manufacturer if your volumes are over even 1k. The process is very automated and the suppliers want to keep their fancy equipment busy.
It not too difficult to get a handle on a random transformer with some simple test equipment and experience. First use an ohm meter to identify the pinout, primary and secondary windings, etc. It might have multiple secondaries, center taps, etc. Measure the DC resistance of the windings, its often quite low, compensate for lead resistance if required. (subtract shorted lead R from readings). By construction (laminated steel), it appears to be a low frequency unit, either audio or AC power. Measure the primary and secondary inductances from the pinout info you got in step one- I would check at 100 Hz, 1k and 10k if you can. A cheap LCR meter or some creative work with a scope and a signal generator will yield good values. The square root of the impedance ratio will give you turns ratio N=squareroot(Z1/Z2). Finally if you have a signal generator of some kind- add a 50 ohm resistor in series with the winding to protect the sig gen from a short and apply perhaps a 1V sine wave signals to primary and secondary and measure outputs, etc. Sweep the frequency up and check frequency response. This will give you a lot of info. This process sounds involved but would only take a few minutes on a well equipped lab bench. If you determine that the inductance is such that you could apply 60 Hz (AC impedance should be relatively high)- start by applying from a transformer, etc. It may not be suitable for AC power but it could be- don't just plug it in. There are other tests you can do like leakage inductance (the uncoupled flux in the core- indicates "tightness"), self heating/power rating. I'll leave these as an exercise. They're all pretty simple once you have the thing on a bench with the equipment setup.
Once you get to this level, you have a decent handle on what you have. I would assume that the isolation spec is 300v, typical for a transformer like this- it can be measured but is a little less simple than the tests so far- look it up if you're interested. You can infer the power capability from the DC resistance of the windings and some load tests. Transformers get warm at full load but shouldn't exceed perhaps 65C - look at some transformer data sheets.
After you've fully documented it, you could sell them on Ebay with your "datasheet", etc for 10x of an unmarked unit! I had a friend in college (many moons ago) that bought surplus transistors for pennies. He had access to a curve tracer in a university lab- he would sort them and sell them to students for 25 cents or so, it wasn't tuition money, more like a few dollars in happy hour money. Have fun.