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Need 30 kilovolts!

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LAN_403

Thomas W

Sat May 19 2012, 12:04PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

wow, nice!

i so want a lil piggie or PT

Dr. Brownout

Sat May 19 2012, 04:32PM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

The 7200 is a tap position. That transformer could be run with 7.2kV or 14.4kV on the high side. Some are rated for only one voltage and others can be used at different voltages.

I would becareful if those transformer are left open like that there are many things that can get into them besides water, bugs like to get in there and arc every once in awhile. So just make sure you clean them good before you use them.

If used dry (without oil) it could ruin them. In oil I have seen them repair themselves by having the puncture swell closed due to the oil being absorbed in to the paper insulation and having the hole swell shut.

--Brian

Oneironaut

Sat May 19 2012, 04:50PM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

Interesting - following the NST advice here, I did some online shopping and it seems I can purchase a new 15kv NST for under $150...

I could run a pair of these in series and end up with 30kv for under $300! This is less than the yard will charge me to load up the 14kv pole pig.

Interesting.
Brad

Thomas W

Sat May 19 2012, 04:57PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

As i said, i really do not recommend seriesing NSTs, they will burn out from what i have heard and many sites say not to do so

Pinky's Brain

Sat May 19 2012, 06:00PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837

Oneironaut wrote ...

I think a flyback may be too small for my project. When I used the pole pig here, I had connected the 120v winding to 120v AC to charge my caps, but this transformer was an oddity, rated at almost 40kv...

Just curious, what happened to it?

How much capacitance do you have to charge and how fast BTW?

Oneironaut

Sat May 19 2012, 06:15PM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

Ok, thanks for the advice on the dual NST.

The pole pig was scrapped when I moved. I actually had 2 of them and did not want the hassle of loading them. The caps are 1uF 50Kv and there are 5 of them in a Marx setup. Charging speed will not be important, but the reversed pole xformer did it in about 10 seconds.

Brad

Newton Brawn

Sun May 20 2012, 09:53PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

If you apply 240 across one 120V primary output to the center tap of a pole transformer, it saturate the core, the current at 240V line increases like a rocket and
PUFFF !
The 240 line breaker trip or the 120V cable burns.
or even nice dammage.

Also if you drainned the oil from the tranformer tank, the insulation is compromized, the pig may work at 14-28 kV, BUT not suitable to deal with impulses..
Remember that pigs are designed to survive to 115~250kV impulses.
Look in that junkyard for a potential transformer (PT) used in high voltage metering or even in switchgear, normaly the primary is 110V, secondary 14, 18, or 23 kV. It is a dry transformer., 300~500W CONTINUOUSLY .
I saw the pictures of your scrap yard, Im sure they have severals PT.
Good look

Oneironaut

Mon May 21 2012, 03:05AM

Registered Member #3616 Joined: Fri Jan 14 2011, 08:47PM
Location:
Posts: 34

Hey, thanks for the tip on the potential transformer. This is the first time I have heard the term, and it seems as though this item is the absolute perfect balance between an NST and pole pig. Large and robust enough for Marx, Tesla, and cap charging work yet not so damn big I need to unload it with an engine lift!

Unless I am reading this plate incorrectly, I should get 22kv out with an input of 110v?...

Xformer1

I think you solved my sourcing problem here!

Brad

Thomas W

Mon May 21 2012, 05:31AM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

that is correct, and damn your lucky! i want one of those

Newton Brawn

Mon May 21 2012, 10:58PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Ok , your PT is complying 100% with my specification...
CongratulationS!
Send more pictures so we can confirm other details.

Of shore, you apply 110V at primary and get 22000V at secondary.
22kV inputing a rectifier/capacitor provide 31kilovolts as required....
NOTE THAT THE SECONDARY CONTINUOUSLY CURRENT IS ONLY 22MILIAMPERES, maybe 100mA for 2-3 minutes.

Allway connect the primary to 110V supply with a resistor of 27 ohms, 400W IN SERIES in order to limit the secondary to 22 mA, protecting the windings. For a short time less than 2 minutes you may use a 6 ohms resistor ...
The resistor 27ohms, 400W may be four 110V 100W light bulbs
The best will be a homemade variable reactor rated 110V. 3A. 5-27ohms. If you have a MOT (microwave ovem transformer) it cam be modified to result in a nice variable reactor.. Let me know !
Regards
Newton
EDIT ! Was this PT storaged in a wet place??? or just lay down in the weather?? throw in the backyard ?
If the moisture reached inside the secondary winding the PT will fail >> PUFF !
Good practice is dry complete before apply 110 volts in the primary. Leave it with a 110V 100W enclosed in a box for 2-3 days, measure the dc resistence with a ohmiter and let me kow.
Other practice is provide a good and effective shot circuit art the secondary terminals and apply 110V VIA 27OHM SERIAL RESISTOR, for 2-3 days. The windings will warm up cleaning the moisture.

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