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Help with transformer

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Hi Guys
This is my 1s post on this lovely forum,and i wish some one to help,i have a transformer all what i know about him is that the output voltage is 12 V and all i want to know is "what's the max output current that transformer can support" if any one has an idea pls help

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Hi nutty boy!

I can tell you right away.. it's impossible, it can be everything from a few mA to several amps  ::)
No one can possibly tell you that if you don't tell us what kind of transformer you have it would just be a huge guess to estimate from one clue "12 volts"
How big is the transformer 1x1m or 5x5cm, what kind of core toroid or laminated EI, wire gauge?
Here is a software you can download and play with:
This software might be a shortcut to estimate your transformers power handling capability  ;D

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  • 2 weeks later...

Hello nutty boy!

Here goes an experiment to measure max output current.
1. Measure o/p voltage or trafo as V1.
2. Put a high wattage low value variable resistance (better use  Rheostat) with max resistance.

3. Decrease load resistence untill you get half of V1 (i.e. V1/2)

4. Take rheostat/load out from circuit and measure its resistance, R1

5. V1/R1 is the max current u can have from this trafo.


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With only half the transformer's voltage at its output, it will be severely overloaded if it is a powerful transformer!

A cheap little transformer might have such poor internal regulation that its open-circuit output voltage drops to half with its rated load.
But a half-decent transformer would have its output voltage drop about only 5% or less.

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Luckily I had oppertutinity to play with 1KVA trafo at my college. I can remeber the load test where we dropped upto near 50% voltage.

Impossible. A transformer is supposed to pass power, not use it. It would smoke if it dissipated 1kW.
A little 9V/200mA wall-wart adapter is sometimes 18V without a load, but with a 200mA load it dissipates only 1.8W.
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Hi guys
  The more I read this form the more i want to start my own thread Called In LayMen Terms.
    fist off nutty boy
          Where did you get the transformer.? If you got it out of a piece of old something there should of been a ratting on either amps or wattage. That might help us.        Or did you buy it from a store? they should be able to tell what it is.
      What kind of test equiment do you have and how much experence do you have?
                          There is a lot of questions we have too. Asking is a good start, so don't stop.

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