help, Discharging a capacitor Banks?

Discussion in 'General Electronics Chat' started by Davidb127, May 5, 2014.

  1. Davidb127

    Thread Starter New Member

    May 5, 2014

    I've been interested in putting together a cap. bank to discharge for some experiments I'd like to do.

    I'd like to be able to discharge the cap. bank repeatedly by pulsing some kind of switch. I understand I'll need to allow charging time but I've run into a problem and I'm not sure what the best path is. I'd really like the circuit to be able to charge the caps up to a few thousand voltage and then discharge. I'm not sure what device would be best for switching. I can't find a transistor rated for more than 1500volts. The best thing I can come up with is a high voltage relay, but I'm worried I will be very limited when it comes to switching speed.

    Anyone have any advice???

    Thanks in advance
  2. bertus


    Apr 5, 2008

    What is your intention with this high voltage discharge?
    What will be the load where the charge is going to?

  3. ian field

    AAC Fanatic!

    Oct 27, 2012
    My home brew zener tester slowly charges a mains reservoir capacitor, its a voltage doubling rectifier so with no load it eventually creeps up to about 600V - with just a shorting switch to make it safe between tests, it just blew the switch contacts away.

    The solution was to put an inrush limiting NTC thermistor in series with the shorting switch.

    Mine was just a random NTC salvaged from a scrap set top box, you may have to select from a supplier if your capacitor bank is very large with a lot of energy to dump.
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    there is a switch designed for this called a marx switch, uses a spark gap to initiate conduction. search "quarter crusher" for info.
  5. wayneh


    Sep 9, 2010
    This topic is not suitable for this forum, for safety reasons, in my opinion.
    Per the Terms of Service:
    "Forum members must not knowingly provide any information that may adversely affect another member; this includes, but is not restricted to, information that may potentially result in injury, death, damage or destruction of property and possessions."
  6. ian field

    AAC Fanatic!

    Oct 27, 2012
    Who can guess why the OP wants to charge caps to a few kV my NTC inrush thermistor suggestion makes dealing with the aftermath relatively safe.

    Once I rounded up a pile of rectifiers and reservoir caps from scrap monitor boards and built a Cockroft & Walton-zilla multiplier - I didn't dare discharge it afterwards, not even with NTCs!

    The only way to deal with the hazard was leave it on a high shelf and wait for capacitor leakage to do the rest.