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Looking for a protective circuit I think...

Discussion in 'General Electronics Discussion' started by ICGengineerTech, Oct 16, 2012.

  1. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
    I have a piece of gear that is powered via a 28 VDC power supply. The gear is also hooked up to a Transient Pulse Generator that will induce voltages, currents, and wave forms that will simulate an indirect lightning strikes.

    In my setup procedure (DO-160) it suggest to use a protective or blocking circuit to make sure the 2000 volt from the generator won't destroy the 28 VDC Power Supply. I am thinking something with zener diodes. I want the 28VDC to come through but any and all other signals (voltage, current, ect.) shouldn't be let through back to the PS. Can anyone help me with this? I am looking for a product I could buy, build, or modify. Thanks so much for any help you can offer.
     
  2. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
    Setup Example

    Where the question marks (? ? ?) are is where the device or circuit needs to be placed. I have little limits on budget however, I don't want to have to spend an arm and a leg on this thing. I could even build it if someone has any idea on schematics somewhere that will serve my purpose. Thanks again for any help you can provide.

    [​IMG]
     

    Attached Files:

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,689
    Jan 21, 2010
    I'm wondering what a current probe is doing where you have placed it. It's not going to measure anything because it is around both conductors. I presume that's a drafting error.

    The underpants gnome box is probably going to be one or more inductors to isolate the low impedance of your power supply from the high frequencies of your pulse (so that the power supply doesn't damp it out)
     
  4. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
    Your absolutely correct. I messed that one up. I was in a rush because it as after 5 and that's quitting time for me. I am at home right now and don't have my normal drawing program. This is something I whipped up using an online program. They didn't have text so the labels are in the font of "6 year old". I basically made it all with curves and lines. This is how the real set-up will look.

    [​IMG]
     

    Attached Files:

  5. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
    I think this is more correct.
    [​IMG]
     

    Attached Files:

  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
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    Jan 21, 2010
    ??? = an inductor. Presuming that the equipment under test does not have a load that has sharp current transients.
     
  7. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
    An inductor is what I thought too. I thought maybe a filter that filtered out the signals put out from the Transient P-Gen. I was researching on how to build this thing when it became crunch time. Now I am looking for something I can just buy outright. My price range is vast... something from 0 to $1,500 or so. It would have to be able to respond fast as the P-Gen is going to pulse at 70uS, 6.4uS, & 500uS. The device needs to be able to block up to 300 or more volts & 450 or more amps.

    Something along the lines of http://www.citel.us/off_grid.html

    Thanks for the help.
     
  8. ICGengineerTech

    ICGengineerTech

    58
    1
    Aug 15, 2012
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,689
    Jan 21, 2010
    I would say that a simple inductor would likely do the job. The issue is the voltage, not the current since (as you know) di/dt will be limited by it.

    You should be able to calculate the effect (the inductor will appear to the signal as being in parallel with your load) with probably not a lot of effort. Alternately you could just measure it.
     
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