how to make the SCR inverter

Discussion in 'General Electronics Chat' started by banozon, May 19, 2008.

  1. banozon

    Thread Starter New Member

    May 19, 2008
    4
    0
    Hi all, I am new to this forum, from Hanoi Vietnam

    Could anyone explain how to make the SCR inverter from AC220V/50Hz to ~10KV/1-2KHz/>100W for Ozone generators

    Many thanhks !

    banozon@yahoo.com
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    First, you'll need to rectify and filter your 220Vac. Next, use your inverter to create the desired frequency - use this to drive a step-up transformer.

    Be extremely careful when working with these very dangerous voltage levels!!! Don't do anything until you are certain of all the hazards and the appropriate safety measures!
     
  3. banozon

    Thread Starter New Member

    May 19, 2008
    4
    0
    Thank's for your reply!

    I'll act with caution, but I don't understand how it work in this circuits:

    http://www.freeinfosociety.com/electronics/schemview.php?id=1599
     
  4. banozon

    Thread Starter New Member

    May 19, 2008
    4
    0
    Fresh Ozone are producing on the surface of the porcelain enamel cup
    Cold Plasma generative at about 6KV 20 KHz 30W (photo)
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,138
    1,789
    I would start by assuming that there is an oscillator with an approximate frequency of 400 Hz.

    Then I would ask how long it takes for a 12V source to charge the 6.8 uF capacitor through a 1K resistor to the gate voltage of SCR.

    When the SCR turns on part of the primary winding is shorted.

    AC current will flow around the loop consisting of the 10 uF, primary winding and SCR. As the current returns to 0 the SCR will shut off.

    Those hints should get you going.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Where would the oscillation come from? Once the SCR starts conducting I don't see what would break the current flow, which is required to turn it off.
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,138
    1,789
    Oops I overlooked the shorted supply when the SCR is on.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Simulation (for what simulation is worth) agrees with the "doesn't work" assessment. At the Free Information Society, you get what you pay for!
     
  9. Papabravo

    Expert

    Feb 24, 2006
    10,138
    1,789
    At least the OP had the good sense to ask about what was confusing him. Considering the reputations of many internet circuit posters I guess we shouldn't be surprised that there is some pretty useless stuff out there.

    The better question might be is there such a thing as a working inverter based on an SCR? Could you build a better one with other components?
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The key would seem to be building an oscillator with an SCR. The only such animal I've found on the net (same schematic copied to more than one place) fails for the same reason as the one at the F.I. site.

    How might we go about making an SCR oscillate?
     
  11. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Far as I can tell, you don't. I have seen SCR's used as transistor like switches in pulsating power supplies, but unless you have something to break the current...

    MOSFETs work better IMO. I've seen simple invertors using transistors using astable oscillator configurations.

    An SCR would work well in a flyback setup I would think, but having never done it I'm not sure.
     
  12. Caveman

    Active Member

    Apr 15, 2008
    471
    0
    I think it works, but you need the right transformer characteristics. The mutual inductance between the top and bottom halves of the primary is probably most important. The inductance of the bottom side of the primary and the capacitor will resonate so that at one point in the cycle the current through the bottom half will take all of the current from the top half, leaving none for the scr, and turning it off.
     
Loading...