Step Down Transformer

Discussion in 'General Electronics Chat' started by will1234, Mar 12, 2008.

  1. will1234

    Thread Starter New Member

    Nov 10, 2007
    8
    0
    Anyone,

    I have a 6500vac (as best as I can tell 7 ma) bug zapper transformer and I need to step it down to about 1200vac before converting it to DC. I believe it would be a 6:1 ratio??? I think I remember reading somewhere that stepping down would lower the voltage but also increase the Ma. I would like to increase the current but must lower the voltage.

    So, the simplest first: Would any place have a 'stock' transformer that would get me near where I need to be? Maybe a doorbell transformer run backward??

    Is there some place either online or other that would likely have a true step down transformer that would work?

    Last resort, is winding your own step down transformer a difficult task? Is there a web site that anyone knows of that I could use to determine the specific details to wind a transformer like I need??

    As always, I appreciate any guidance anyone can give me.

    Will
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    281
    That would be a 3:1 ratio.

    It might be easier to simply pervert a step-down transformer. A 12 volt secondary is 1/10 the 120 VAC input. So, placing the 120 VAC to the 12 volt winding should give you close to 1200 VAC out. Make sure the transformer has a hipot rating of at least 5000 volts before you try this.

    Please be very careful around high voltages.
     
  3. lilfrankywilding

    New Member

    Mar 12, 2008
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    its a 5.4 to one ratio man! where do you see three to one
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Carry over from the previous answer I posted.
     
  5. will1234

    Thread Starter New Member

    Nov 10, 2007
    8
    0
    Looking on DigiKey, Mouser, and assorted other sites I can find 12 volt step down transformers which make no mention of hipot so I have to assume that they aren't. Does anyone know where I might have better luck finding a hipot step down? Is there anything in everyday life that would have one I could cannibalize?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Instead of trying to step down your "bug zapper", why not try building your own flyback transformer & associated circuitry?

    Here's a good & informative "how to" page on that very subject:
    http://www.dos4ever.com/flyback/flyback.html

    Even gives a "how to" on building an inductor test bench.

    Just be really careful to not zap yourself or your equipment. Read & heed the safety tips.
     
  7. will1234

    Thread Starter New Member

    Nov 10, 2007
    8
    0
    I'll give this a try, thanks. Concerning the transformer I was trying to find a 12v step down that I could run backwards on 110v and get into the 1200v range that was suggested above. Finding one that is hipot that wouldn't melt down is the problem I dealing with.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, the hipot is definitely a problem.

    But, there's no reason you can't scavenge and wind one yourself.

    Be sure to insulate well between the layers of secondary windings, or there will be a bright flash and smoke in your future.
     
  9. Xray

    Well-Known Member

    Nov 21, 2004
    58
    1
    Just so I understand what you are asking.... You want to run 120 VAC into the 12 VAC winding so that you can get 1200 VAC ouput on the secondary (which WAS the 120 VAC primary)? If that's what you are asking, then NO, it will not work! You will smoke your transformer, and probably pop the circuit breaker that protects that particular circuit. The reason why it won't work is because the inductance is much too low on the 12 Volt winding to put 120 Volts into it. And even it it did not smoke, 1200 volts would likely arc across the windings like crazy and burn out the transformer that way.
     
  10. recca02

    Senior Member

    Apr 2, 2007
    1,211
    0
    Using a low rated transformer can be a problem as..
    connecting 1200 V to some low resistance system(simply high power device) will send a huge current.
    then there is the insulation problem 1200 volts might overcome the insulation and there will be current in the entire core of the transformer( perhaps even body) and possibly lot other problems..
     
  11. wes

    Active Member

    Aug 24, 2007
    242
    2
    well I dont know how efficient it would be but couldn't you just use a voltage divider circuit that is able to withstand the voltage's you are using and the total power of that 6500V 7ma transformer is only like 45.5Watts . although it would probably be better using a step-downtransformer and probably alot less chance of a shock. eithier way be very careful with voltages that high
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    A step-down transformer would increase the current while reducing the voltage.
    A voltage divider circuit would decrease the current while reducing the voltage, as well as dissipating power as heat.
     
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