All About Circuits Forum Step Down Transformer
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#1
03-12-2008, 03:42 PM
 will1234 New Member Join Date: Nov 2007 Posts: 8
Step Down Transformer

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
03-12-2008, 03:50 PM
 beenthere Senior Member Join Date: Apr 2004 Location: Missouri, USA (GMT -6) Posts: 15,815 Blog Entries: 10

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
03-12-2008, 10:35 PM
 lilfrankywilding New Member Join Date: Mar 2008 Posts: 1
yo wassup dog

its a 5.4 to one ratio man! where do you see three to one
#4
03-12-2008, 11:24 PM
 beenthere Senior Member Join Date: Apr 2004 Location: Missouri, USA (GMT -6) Posts: 15,815 Blog Entries: 10

Carry over from the previous answer I posted.
#5
03-18-2008, 11:44 PM
 will1234 New Member Join Date: Nov 2007 Posts: 8

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
03-19-2008, 01:27 AM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,031

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.
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#7
03-19-2008, 06:18 PM
 will1234 New Member Join Date: Nov 2007 Posts: 8

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
03-19-2008, 06:46 PM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,031

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.
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General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
#9
03-23-2008, 11:34 PM
 Xray Member Join Date: Nov 2004 Posts: 59

Quote:
 Originally Posted by will1234 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.
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
03-24-2008, 10:06 AM
 recca02 Senior Member Join Date: Apr 2007 Location: India-22.35° N 82.68° E. Posts: 1,211

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..

 Tags step, transformer

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