Need plans for 16kv .50amp transformer, please.

[teslaman]

I build tesla coils and am moving on to my latest masterpiece, which will be a 2'x6' coil, and spending $800 on a pole pig is not an option for me, so I need to build it. I do not want to spend a month on research and calculations, and since it's duty cycle is so short, it need not be super efficient, just tough. Just some quick down and dirty specs. I will be starting with 240v, of course, as it will be high current. So, I would need the following-  core size, primary wire gauge, secondary wire gauge etc. I expect I will use EI laminates, but am open to suggestions. Keep it simple for me, I don't need a bunch of theory to wind one transformer. This one will be loaned out to churches and schools for presentations. I am retired on social security, and we all know no tax money makes it to the schools, so basically you will be helping out with charity work for kids. Thank you, and god bless. some pics of my 120v 35amp coil

[Gyro]

Without in any way trying to dampen your excellent intentions, your mention of loaning out to churches and schools makes me wonder about your personal risks in a litigious land like the US.

Have you looked into the cost of public liability insurance (or the US equivalent). Just something to think about costing before you get too far into the project.

I'm really sorry I can't offer you any useful guidance in the safe construction of a HV transformer of that capacity.


P.S. Welcome to the forum.

[bob91343]

First of all, a reality check.  If you multiply 16 kV by 0.5 A you find that you have 8000 Watts.  If efficiency were 100% that would draw about 30 Amperes from a 240 line.

I suspect you don't need that much.  And if you do set up a Tesla coil at that power level, you will destroy communications in a rather wide area, besides breaking the law.

If you want to build a transformer to operate from a 50 or 60 Hz line, you will first need a core onto which to wind the primary winding of sufficient inductance to avoid saturation of the core.  And still leave room for the secondary winding.  The secondary winding will need 16000/240 times as many turns as the primary.  That is perhaps 70 times the number of primary turns.

Complicating the situation is the fact that 16000 volts is very high.  It's not only dangerous but requires special insulation techniques, as ordinary paper or mylar will not withstand that high a voltage.

You could save yourself a lot of trouble by locating an old neon sign transformer.  Still, personal safety is a major issue.

My summation is this: You want to build something without learning the details of what you are doing, and the result is to be something dangerous to life.  I strongly suggest you reconsider your plan and find some other dazzling spectacle to create.  It does appear that you are looking for something sensational, and perhaps your motives aren't as lofty as you claim.

[Stray Electron]

  I can't see even the remotest chance that a school or church or any other institution or business would allow something like this to be connected to THEIR power system or to be operated on THEIR property. Particularly something that was home built by someone that doesn't have the slightest clue about what he's doing and someone that clearly isn't interested in learning how to build what he wants or in spending the money to buy a proper piece of equipment.

   Did I miss anything?

[Bud]

You could save yourself a lot of trouble by locating an old neon sign transformer.

There you go

https://youtu.be/uCm1iPLVe8I

[MagicSmoker]

...spending $800 on a pole pig is not an option for me...

You want 8kVA at 60 Hz for less than $800? And with a HV secondary? Yeah, better buy the pole pig*.


* - for our non-US members, "pole pig" is a colloquialism for a pole mounted distribution transformer, typically rated for 10kVA to 50kVA.

[Stray Electron]

  The OP seems to be obvious to the fact that large Tesla coil builders use pole pigs for a reason!

[ArthurDent]

The stunning lack of basic knowledge displayed in asking for information in trying to construct what might end up being a death ray leads to only one conclusion. Don't under any circumstance try this.

[Stray Electron]

You could save yourself a lot of trouble by locating an old neon sign transformer.

There you go

https://youtu.be/uCm1iPLVe8I

    That transformer is only rated at 60mA and the OP wants 500mA.  The largest neon sign transformer that I've ever seen (out of 100s) was 15,000 volts at 30mA.

[profdc9]

The amount of power you are considering using is just far too dangerous to be used in all but the most controlled environments.  Also, that amount of power is probably only going to be available from three-phase sources.   Which is exactly what a pole pig is designed for.

I have built a smaller Tesla coil from dual microwave oven transformers that can operate off of a single AC outlet.  Dual MOTs can be voltage doubled using a Villard doubler to reach about 12 kV peak, with the frames of both MOTs joined to put the two voltages in series to make a balanced output.  If a rotary spark gap is built carefully (with dual gaps of 1 to 1.5 mm) then it can be made to reliably trigger with this source.  I used an angle grinder to rotate the electrode wheel.   It can be quite tricky, however, to get such a thing working because you have rapidly rotating parts that have to be balanced very well and not fly to pieces.  If you power each MOT from separate circuits, you may be able to push the power you can draw from the MOTs to 5-6 kW, but the MOTs are going to get hot!

Alternatively, I build a dual resonant solid state tesla coil.  It actually ended being cheaper, and in some ways easier, to build than the spark gap tesla coil, as there are no moving parts, and you can make it play music as well.  However you need an oscilloscope with a high voltage probe to tune the timing of the bridge circuit.  The oscilloscope probably costs $400 but is a worthwhile investment, and a Hantek high voltage probe costs $30.

But the amount of power you are talking about is crazy, unless it is in a controlled environment like a museum exhibit where precautions can be taken if catastrophic failure occurs, the spectators are at a safe distance, and the amount of power necessary can be supplied reliably without risk to the local electrical network.

[Zero999]

I thought pole pigs are single/split phase in the US? Pole mounted transformers are rare in the UK and I believe both single and three phase units exist, although the latter are more common here.

Transformers that size, cost that much due to the price of the the raw materials i.e. copper and steel. Building your own won't save you any money and might cost more, since you won't be able to purchase the raw materials, as cheaply as a transformer manufacturer will. The only way to get it cheaper is to look for a scrap/second hand unit and refurbish/repair it.

[T3sl4co1l]

Substitute for "pad transformer" (we have those too), or whatever is more common.  Hm, give or take the availability of 3ph over there, which may make 1ph transformers of that size actually less common?

The amount of labor spent will certainly be more than the cost alone, even if you severely discount your labor.  You're better off spending your time on something higher level -- something more fun than winding a transformer, and far more profitable -- and using the proceeds to buy into the traditional route.

Tim

[LaserSteve]

Take it from a former teacher turned senior technician at a university, who did school  laser physics demos for a long time.  You'll be doing good to find an outlet in a US school capable of sourcing  500-700 watts without tripping a breaker. The 15 Amp residential or 20 Amp industrial circuit your expecting will be maximally loaded before you get there, usually has a floating ground, and will be installed with the longest possible run of the lightest guage wire possible.  Dont even expect a power outlet on the stage, even if they have theatrical lighting installed. Least bidders dont put much effort into school wiring.


Most states have a central funding board that limits spending during school construction. The limits they put on infrastructure costs are mind boggling, often with one breaker covering 3 classrooms. NEC requirements somewhat go out the window in an institutional setting. AT least in the Midwest it does.


Steve

[Stray Electron]

   I was thinking the same thing.  In the US other than in industrial facilities, high current 230 VAC is only available for things like electric clothes dryers, central heating (which is built in and has no outlets) and electric ovens.  Even if the facility that OP wanted to run his TC at would let him, he'd probably be hundreds of feet from the nearest 230 VAC outlet and a large high amperage extension cord would be extremely expensive and he wouldn't be allowed to run it anywhere that the public would be present (he wouldn't be allowed to run it out of the cafeteria and down the hall and out the door and across the parking lot!) Given the scenario that the OP proposes, I would expect that the needed extension cord would costs MORE than the $800 pole pig.

[duak]

Here's a link to Tesla coil safety - note the sections on UV generation and Pacemakers: https://webhome.phy.duke.edu/~rgb/Class/safety.html

If the OP is serious about the original specs, the arc is going to be pretty impressive all by itself.  The electrodes are likely going to get really hot, erode and probably deposit themselves on the inside of any containment.  I'll bet a borosilicate or even quartz tube will be needed.

[coppercone2]

i think you need a cage room with interlocks and a remote property for this kind of thing. like the geek group used to have this setup for the thumper

i think the authorities would want to bust that just for the news paper picture of a gigantic arc machine with some cops in front

[teslaman]

Yes, exactly, 30 amps. I don't mess around. My current one uses four 15,000v 60ma neon sing transformers and is just flat scary, this will be my masterpiece.

[Illusionist]

That might well be your epitaph too!

Still, I would love to see the thing fire up, from a distance.

[teslaman]

I have seen them three times this size, if I had the property to build a barn and $10,000 to spend on copper wire, that would not be out of the question either. I had to disconnect all the power lines on one side of my garage to run my current one. You should see arcs flowing through an 8"x8".

[teslaman]

It will be about 35lbs. of EI laminates, I will just build a spool out of cardboard and wind the coils on my 16"x72" south bend lathe, I have it setup with a variable frequency drive with a foot pedal. Makes it nice for winding 1200 wraps of 24ga wire on a 4" secondary coil. Looking at about 80 dollars in iron core, and probably three times that in copper. Well under $800, and much tidier. I just built a 2 volt 400 amp transformer for electroplating machined parts. Just the opposite of this one. I may end up buying another industrial tig welder, and scrap it, they would have the perfect cores, might even get lucky and be able to reuse a primary.

[teslaman]

I have been doing this a long time, as far as tesla coils go, insurance companies don't get too excited, it was the crocodiles and pythons we use to bring that caused concern.

[teslaman]

You mean, like these four 15,000v 60 ma ones, $600 for the 4. Impressive, but gotta go bigger, it's the American way. I build my transformers now. Smaller, cheaper and no sense having something rated at 100% duty cycle that will only run for 2 minutes at a time. Waste of money and space.

[teslaman]

It will use a 12" rotary spark gap with 1/4" tungsten electrodes with high velocity quench fan, and will produce copious quantities of ozone and nitric oxides as well as be too loud to hear a person standing next to you yelling.

[teslaman]

Ya, old industrial tig welder would be perfect.

[teslaman]

It,s not winding the transformer that's fun, it's the look on mens faces when I flip the switch, homemade lightning, very cool. When I turn on my 4" coil, I turn off the lights in the garage, but all the fluorescent ones light up anyhow. No, will not stop a pacemaker, and you can take pics with phone and they survive, don't think I would want it near my computer though. Check it out, but careful, coilings addictive and before long you fing yourself pricing capacitors by the 100 lot.