Pulsed Power Circuit

Discussion in 'Power Electronics' started by beginnerDesigner, Sep 15, 2016.

  1. beginnerDesigner

    Thread Starter New Member

    Sep 15, 2016
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    0
    Hi,

    I am trying to model a circuit to represent charging a capacitor then a switch flipping and discharging through a resistor. I am able to get the capacitor to charge to the voltage I need, but there's not enough energy when I discharge. I've increased the capacitor size hoping to get more charge but that just lowers the voltage. Are there any ideas on how to get the energy in the capacitor increase within a limited time and not decrease the voltage?
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    375
    You will need to increase the charge current.
     
  3. beginnerDesigner

    Thread Starter New Member

    Sep 15, 2016
    3
    0
    Ok thanks. I'll try to figure out how to do that.

    if I want Q = 1.65 kJ and V = 25 kV...Q = V*C so C = 1,650/25,000 = 66 mF. Now if I want to charge that in 20 us, I know that tao = R*C and a full charge (1.65 kJ) is at 5*tao right? So tao = 4 us.

    So R = tao/C
    R = 4us/66mF
    R = 60.6 micro-ohms.

    When I plug this in, the voltage is limited to somewhere 400-600 volts. Far less than expected. Any ideas why or how I could tackle this problem?
     
  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,886
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    The maths is right. Though the charging current of about 380,000 amps from a 25kV source is very scary.
    What are 'plugging' all this into?
     
  5. beginnerDesigner

    Thread Starter New Member

    Sep 15, 2016
    3
    0
    I'm just simulating it in spice. lol this isn't real. I'm just trying to figure out why my theoretical circuit wasn't working right.
     
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,886
    375
    This is the LTspice version of the charging which seems to behave properly.
    upload_2016-9-16_15-56-18.png
     
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