# Need help finding a transformer

Discussion in 'General Electronics Chat' started by NTkiller, Aug 6, 2013.

1. ### NTkiller Thread Starter New Member

Aug 6, 2013
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I'm looking for a transformer to step up 120V AC to 1000V AC, but I cannot find anything. It does not have to have a high capacity, as I think I will only need to send 15 watts across it. I'm going to connect this to the input side of a homemade voltage multiplier to power a Crookes tube. I've looked everywhere, but I cannot find a transformer that does what I want. Any help would be appreciated.

2. ### RRITESH KAKKAR Senior Member

Jun 29, 2010
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use any good transformer any rating say:
12V to 120V
at the place of 12V give 120V at output it will be ~1200V but at less current that mean not so much load or have nice transformer.

3. ### NTkiller Thread Starter New Member

Aug 6, 2013
18
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I looked into that, but another place on the web said connecting 120V AC to the low side of a 120v to 12v transformer will just blow the low side windings up. another thing I was thinking of was having 2 voltage multipliers in series, but I would need to find a way to convert the DC back into AC. Thanks for the idea, though. By the way, how hard would it be to make a homemade transformer, because I've got nearly a mile of magnet wire I salvaged from the secondary of a microwave transformer?

4. ### LDC3 Active Member

Apr 27, 2013
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Actually, you would need to ensure to restrict the current. Since the transformer was designed to step down the voltage, the primary windings would restrict the current from a 115V source. There would not be any extra resistance to the secondary side, so if you attached 115V to that side, you would practically short the power through the transformer. Unfortunately, because of the resistance, the performance of the transformer would probably be below 50%.

5. ### NTkiller Thread Starter New Member

Aug 6, 2013
18
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I got an idea the other day: I could make one voltage multiplier to make the initial 1000 volts needed for the second voltage multiplier, but I would need some circuit to convert the DC back into AC. Got any ideas?

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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Perhaps you could share with us the intended application and we might have some other suggestions.

Mains originated 1000V is not a trivial voltage to be utilizing. It's potentially quite hazardous. I'd like to know more before offering any advice.

7. ### NTkiller Thread Starter New Member

Aug 6, 2013
18
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I thought I mentioned this already, but I'm going to use this to power a homemade Crookes tube. I want a power supply built just for this purpose since I want to use it as a decoration. I already have a microwave transformer, and I could use it but I don't want to use it because:
A. I could very well kill me. the ratings say input is 120v @ 10 amps, or 1200 watts, and the output is at 4000v. I calculated it out, and it can provide that 4000v at 0.3 amps, which is way more than enough to stop someone's heart. What I am going to build is 10,000v at 1.5 milliamps, which I looked up is just a little above the pain threshold. What I want to do is safe, as long as I make a safe power supply that can limit it's output current in case it shorts out to my hands
B. The microwave transformer is so big that it gives OVERKILL a whole new meaning. I don't want to power a tube the size of a canning jar with a transformer heavy enough to crush said tube. That, and if I wanted to put the entire deal in a decorative box, I would lose my microwave transformer, which I sometimes use for other stuff.

So I had another idea, but it seem no one has read my other post on it. What if I made one voltage multiplier to make the initial 1,000 volts, then invert the output back to AC then make a second voltage multiplier to step up the output of the first multiplier to the final 10,000 volts I need. So, once again, any ideas?

8. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Did you know that Crookes tubes also emit X-rays, and for safety reasons might not be a great thing to experiment with?

Snippet from Wikipedia:

I happen to have an actual General Electric Coolidge X-ray tube from the 20's that's in very good shape - but I certainly know enough to not try to power it up. Oh, and this beast takes 300KV on the anode...

9. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,402
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Irradiation has been known to cause auto immune disease, lung cancer (non-smokers), liver cancer, pancreatic cancer, prostate cancer, testicle cancer, and others.

We can't stop you from doing whatever design you want. That is up to you.

10. ### NTkiller Thread Starter New Member

Aug 6, 2013
18
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Just so you know, I know about the dangers of x rays. Since I am going to be making the tube out of a glass bottle, I am going to vacuum out just enough air to make it glow. Plus, I'm also going to coat the inside of the tube with phosphor so it will light up brightly. This will reduce, if not eliminate the X rays exiting the tube.

Back on the subject, I found a travel transformer on ebay that converts 120v AC to 240v so people in the us can operate equipment purchased overseas without modification. I found out that with 6 stages of multiplier powered by 240v will be plenty enough voltage for what I'm doing. Where could I find a 120 to 240 step up transformer like one of those for cheap?

11. ### richard.cs Member

Mar 3, 2012
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Feeding 12V into the 12V winding would give you about 110V on the output, the 12V winding will have extra turns by maybe 10% so it's more like 1:9 rather than 1:10. Feed 24V in say and the transformer will saturate and you won't ever get much more than about 150V out however much you put in.

The way around this is to increase the frequency. In pronciple you could feed 120V into the 12V winding if you did it at 600 Hz rather than 60. In practise 1) that's a pain in the backside, and 2) the insulation will probably breakdown and the transformer will fail.

Two options are open to you:
1) A bigger multiplier, say 8 stages. Or 4 if you can run it off 240V. This is how I would do it but then I live in a 240V country.
2) Use transformers that have good isolation between primary and secondary. Step down to 12V say then step up with several transformers putting their low voltage windings in parallel but their secondary windings in series. If you use split-bobbin transformers you should be able to get a few kV before they flashover primary-secondary.

A variant on the second option might be to get five identical 240:24V transformers, again with good primary-secondary isolation. Wire the 24V windings in series across 120V and the secondaries in series to get about 1200V.

NTkiller likes this.
12. ### shortbus AAC Fanatic!

Sep 30, 2009
4,095
1,685
Why not use a neon sign transformer? Used ones are fairly cheap and they are made for the voltage and purpose.

Nov 29, 2005
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14. ### NTkiller Thread Starter New Member

Aug 6, 2013
18
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I think what I'm going to do is buy a 120 to 240v travel transformer off ebay (\$6 shipped), gut it and wire it's output to a big multiplier. Thank you all for your suggestions.

15. ### szhighstar New Member

Jun 26, 2012
27
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it is step-up transformer, please advise input currentand work frequency and dimension requested, can custom and design the transformer.