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Capacitor discharge through a coil, need to find current

  1. Nov 13, 2009 #1
    I'm designing a circuit to discharge a capacitor though a coil of wire to make a large magnetic field, which is basically an undriven RLC circuit which starts out with a charged capacitor in series with an inductor and a resistor (the coil having a certain resistance in addition to its inductance).

    I'm trying to find an equation for the current through the coil (inductor) as a function of time after starting to discharge the capacitor. I need to find this so I can select proper components to give a sufficient magnetic field without burning out the coil.

    I also know that the capacitor will have a small amount of inductance which needs to be factored in. Please let me know if there is anything else like that I would need include in the calculation.
     
  2. jcsd
  3. Nov 13, 2009 #2
  4. Nov 13, 2009 #3
    Thanks Bob,

    That thread was helpful, I think if I had that program you were using I could figure out what I need to know. What's the name of that program, and do you have that RLC circuit file you made that you could send me if I can get the program?

    -Nick
     
  5. Nov 13, 2009 #4
    Hi nrlightfoot-
    I was using free LTSPICE IV available on the web. Please look at my posts #26 thru 32 in the referenced thread:
    https://www.physicsforums.com/showthread.php?t=327153
    Here is a 16,000 amp, 2 ms wide half-wave current pulse using series diode in thumnail.
    Bob S
     

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    Last edited: Nov 13, 2009
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