Need plans for 16kv .50amp transformer, please. - Page 1
Forum section: electronics / projects

author: teslaman
author_rank: Contributor
timestamp: September 05, 2019, 05:43:22 pm
content: 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

author: Gyro
author_rank: Super Contributor
timestamp: September 05, 2019, 06:44:07 pm
content: 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.

author: bob91343
author_rank: Super Contributor
timestamp: September 05, 2019, 06:58:23 pm
content: 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.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 05, 2019, 07:00:35 pm
content: 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?

author: Bud
author_rank: Super Contributor
timestamp: September 05, 2019, 07:47:37 pm
content: Quote from: bob91343 on September 05, 2019, 06:58:23 pmThere you gohttps://youtu.be/uCm1iPLVe8I

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 05, 2019, 08:10:44 pm
content: Quote from: teslaman on September 05, 2019, 05:43:22 pmYou 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.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 05, 2019, 09:02:50 pm
content: The OP seems to be obvious to the fact that large Tesla coil builders use pole pigsfor a reason!

author: ArthurDent
author_rank: Super Contributor
timestamp: September 05, 2019, 09:16:53 pm
content: 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.

author: Stray Electron
author_rank: Super Contributor
timestamp: September 05, 2019, 09:20:52 pm
content: Quote from: Bud on September 05, 2019, 07:47:37 pmThat 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.

author: profdc9
author_rank: Frequent Contributor
timestamp: September 05, 2019, 11:09:54 pm
content: 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.

author: Zero999
author_rank: Super Contributor
timestamp: September 06, 2019, 09:40:08 am
content: 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.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 06, 2019, 10:57:38 am
content: 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

author: LaserSteve
author_rank: Super Contributor
timestamp: September 06, 2019, 02:33:58 pm
content: 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

author: Stray Electron
author_rank: Super Contributor
timestamp: September 06, 2019, 07:23:10 pm
content: 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 behundredsof 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.

author: duak
author_rank: Super Contributor
timestamp: September 06, 2019, 08:56:31 pm
content: Here's a link to Tesla coil safety - note the sections on UV generation and Pacemakers:https://webhome.phy.duke.edu/~rgb/Class/safety.htmlIf 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.

author: coppercone2
author_rank: Super Contributor
timestamp: September 06, 2019, 09:39:39 pm
content: 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 thumperi think the authorities would want to bust that just for the news paper picture of a gigantic arc machine with some cops in front

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 12:22:00 am
content: 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.

author: Illusionist
author_rank: Regular Contributor
timestamp: September 07, 2019, 12:58:07 am
content: That might well be your epitaph too!Still, I would love to see the thing fire up, from a distance.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:08:52 am
content: 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".

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:20:49 am
content: 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.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:31:36 am
content: 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.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:37:32 am
content: 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.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:44:56 am
content: 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.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:46:38 am
content: Ya, old industrial tig welder would be perfect.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 01:55:12 am
content: 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.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 02:03:36 am
content: A simple, no teslaman, I do not know the wire gauge sizes recommended, nor the spool size you will need, would have done just fine.

author: teslaman
author_rank: Contributor
timestamp: September 07, 2019, 02:16:29 am
content: Cleaning out the cobwebs, I clearly need a taller garage, arcs travel through the timbers and back out to anything grounded.

author: BravoV
author_rank: Super Contributor
timestamp: September 07, 2019, 02:32:47 am
content: Are you doing a live streaming thru forum posts ?

author: MagicSmoker
author_rank: Super Contributor
timestamp: September 07, 2019, 10:57:34 am
content: Quote from: teslaman on September 07, 2019, 02:03:36 amOh, plenty of people here know how to build your transformer, but they also know it will cost you more to DIY it than buy a used/surplus pole pig.For example, this equation determines the number of turns vs. RMS voltage, core area in m2, and peak flux density in T at 60Hz:N = Vrms / (266.4 * Ae * B)The larger the core area the fewer turns are needed to support the primary voltage at a given flux swing; something to keep in mind given the secondary will need something like 62x more turns (and will likely need to be wound in separate - or "Pi" - sections, thereby requiring even more room).You want to use a C-core for a HV transformer, rather than E, because winding the primary and secondary on opposite sides of the C-core will provide much better voltage withstand capability vs. winding them concentrically or adjacently, as would be needed on the E-core; the increased leakage inductance of the C-core winding arrangement is also a plus here, as it will help limit short circuit current. I'd also say your estimate of needing 35# of laminations is about half off, though with a low duty cycle it might be okay. You will also likely have to wind the secondary in "Pi" fashion using quad-build #26 or #28 magnet wire (MWS is my preferred supplier for such), especially if you can't vacuum impregnate the windings.So given all that a potential core would be one or two pairs of this one from Bridgeport Magnetics at a cost of $167 (not incl. shipping) per pair:https://www.bridgeportmagnetics.com/shop/cd40x80x200-c-core/The core area of one pair is 3.15" x 1.64" = 5.166 sq. in. = 33.33cm2= 0.003333m2So for a 240Vrms primary and 1.5T peak flux density you'll need 180 turns of wire, and to handle 33Arms the primary wire will need a cross-sectional area of around 7-9mm2(roughly equivalent to #8 AWG). The secondary will need ~62.5x more turns with a cross-sectional area of around 0.125mm2(equiv. to #26 AWG), and will likely need to be wound in five Pi sections of 2250 turns each, with either an appropriate air gap between each section or using a good insulating material (mica, PTFE, glass, etc.).This is an awful lot of turns to handle on the secondary, and I didn't even check to see if the window area would be sufficient for the above winding specification, but I suspect you'll either need to double up on the cores to cut the number of turns in half, or else cut the cross-sectional area of the wire in half and accept very high I2R losses (which would be okay for very low duty cycle operation - say, 30 seconds on followed by 3 minutes off).You might still need to immerse the transformer in dielectric oil and vacuum purge any entrapped air bubbles both for cooling and voltage withstand reasons, otherwise you could go the "dry" route and vacuum impregnate with varnish/shellac (polyurethane can work for a one-off like this).Etc. and so on... Hence why the general consensus has been to just buy the pole pig.EDIT - correct duplicate sentence

author: Zero999
author_rank: Super Contributor
timestamp: September 07, 2019, 01:40:12 pm
content: Quote from: teslaman on September 07, 2019, 01:37:32 amIf you want to add more, please use theModifybutton, rather than flooding the thread with multiple posts.You should have said what duty cycle you needed, in the first post. It still will be more expensive than you think. A low duty cycle only means less copper. The same amount of steel is required to avoid core saturation.

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: September 08, 2019, 11:23:33 am
content: Quote from: teslaman on September 07, 2019, 02:16:29 amHow do you manage to only take blurry photos, calm down a bit before taking the photos

author: ArthurDent
author_rank: Super Contributor
timestamp: September 08, 2019, 03:02:38 pm
content: https://youtu.be/EO4AvHI7ZCg