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Measure Transformers

Discussion in 'General Electronics Discussion' started by Yoa01, Nov 25, 2012.

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  1. Yoa01

    Yoa01

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    Jun 18, 2012
    Hi all,

    So I have a number of small and somewhat large transformers and would like to know how to measure them. Identification is futile as transformers are typially custom for each application (and, I've tried and failed), but all that's really important is knowing voltage and current input and output. Is there any way to measure this?

    Only way I can see is to apply power to one side and measure with a volt meter, but I feel as if that would result in various dangers and problems, such as fire, shock, and destruction of the transformer, power source, and/or volt meter. Any better ideas?

    Thanks in advance.
     
  2. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    There are many kinds of transformers.
    Mains
    Intervalve
    Speaker
    Inverter
    Pulse
    High voltage

    Taking mains transformers.
    Find the windings with a meter.
    Measure the winding resistances.
    Put 6V across the highest resistance winding.
    Measure the voltage across all windings.
    Calculate the turns ratios.

    You may now be able to guess the primary winding, Connect to the mains via a light bulb to limit the current and measure all voltages.
    You can get an idea of the permitted current from the winding resistance, compare with a known transformer.
    You can get an idea of total transformer power by comparing the weight with known transformers.

    Use an isolating transformer.
    Connect up then switch on remotely.
    BE VERY CAREFUL.
     
  3. Yoa01

    Yoa01

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    Jun 18, 2012
    Thanks! I'll try that.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Hopefully it is obvious that this is 6VAC.
     
  5. Yoa01

    Yoa01

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    Jun 18, 2012
    It is. I just need to find such a power source.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Some low voltage AC source should be fine. Just as long as you can measure it and compare it to what appears at the other side(s) of the transformer.
     
  7. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    ... And be very careful how you measure "the other side(s) "
    there may be in excess of 100VAC. keep fingers away from probe tips and transformer leads. Preferably use some crocodile clip leads between the meter and transformer leads

    exercise the saying of an old and wise technician ... keep one hand in your pocket

    Dave
     
    Last edited: Nov 26, 2012
  8. Yoa01

    Yoa01

    214
    0
    Jun 18, 2012
    I assumed as much. Most of these are power transformers, so if I want to live I figure safety is helpful :)

    At the moment I'm finding a way to create a 6VAC source. Literally everything I have is DC, aside from wall power which I don't even want to try messing with. I've been shocked by 240V, but through a messed up ground connection on a gas dryer. I don't want to know what full 120V power feels like.
     
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