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Can a 220v transformer store electiric charge?

  1. Sep 25, 2009 #1
    i turn off the transformer i assembled its from a 220v power source i touched the primary windings and surprisingly it gave an electric shock. i never know this things store charges like capacitors, how does this happen? any explanations?
  2. jcsd
  3. Sep 25, 2009 #2


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    Staff: Mentor

    That's a bit weird, but maybe the charge was stored in the parasitic capacitance of the secondary windings. With the transformer fully discharged and not connected to anything on the primary, what do you measure the secondary capacitance to be?
  4. Sep 25, 2009 #3


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    Science Advisor

    Is the case grounded? You might've built up some charge walking around, bouncing your leg, etc.
  5. Sep 25, 2009 #4


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    Science Advisor

    Transformer windings have capacitance to the frame and usually capacitance to each other because they are just two pieces of metal separated by a dielectric.

    Large mains transformers tested at high DC voltages have to be discharged before they are safe as they can hold lethal charges for many days otherwise.

    I just tested a small 250 volt transformer primary and it had 150 pF capacitance to the transformer frame. So, it isn't likely to be a problem in normal use, but you could still get a small zap off it.
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