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Transformer Short Circuit Current?

Discussion in 'General Electronics Discussion' started by Cburg, Nov 24, 2012.

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  1. Cburg


    Nov 24, 2012
    Hi Forum,
    I am designing a capactive discharge circuit that pulses current into an inductor. To charge the caps, the input transformer sees near "short circuit current". I have found that with a small transformer the current is limited about right just by the high impedance of the transformer. I now need to find a bigger transformer, but cannot find the impedance or short circuit current specs on the transformers. Are there any guidlines for knowing about what these parameters might be; like 10X the rated current, or something?
  2. john monks

    john monks

    Mar 9, 2012
    I am not clear what the application is. I am not aware of transformer specifications for maximum input current in a capacitive discharge system. But your question implies to me that you intend to run your transformer to such a high rate that your concerned with overheating.
    Is this the case? Normally with a capacitive discharge system you are more concerned with exceeding the secondary maximum voltage rating, not the primary. It is very difficult to damage a primary winding with a capacitive discharge system. The only transformers that I know that might have maximum input current ratings in this application are automobile coils. Normally when testing a transformer in such application I deliberately exceed the voltage ratings just to see what I can get away with. And usually the secondary arcs internally. And sometimes, but rarely, this damages the transformer. Is this for a switching power supply or automobile ignition system? Are you thinking in terms of saturating the core?
  3. Rleo6965


    Jan 22, 2012
    What is the frequency of your dc inverter? You don't need big transformer for cdi using high frequency dc inverter..
    Last edited: Nov 24, 2012
  4. Cburg


    Nov 24, 2012
    Hi Guys,
    The application is a magnetic pulser to generate a magnetic field. Frequency is .5 Hz to 10 Hz with two different capacitor ranges. The caps draw near short circuit current on charging with the transformer I have now, and limits the current well, but at the higher frequency, it overheats. I measured current and it is 6x rating, so have ordered a larger one accordingly (plus a little). I think I will need to use a current limiting resistor also, now, but don't know what to expect.
    Thank you!
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