Help Identify Large Transformer - Page 1
Forum section: electronics / beginners

author: Xsfacade
author_rank: Newbie
timestamp: June 08, 2013, 10:27:07 am
content: I am a PhD candidate in quantum mechanics and need help identifying a medium to large transformer. I found a scrap metals dealer, e metals in kent wa, that sells used electronics at scrap metal prices. I picked up this piece for $5.00 for my main thesis project. I thought it would have markings somewhere but darned if I can find them. It tested ok for closed circuit but without specs I am afraid to try and wire it up or test it under any load. They did not have the lid in the bin. Considering the fact this was a small one compared to what they have on hand I thought it was worth the money either way. Aside from identifying it I wanted to ask if there is a way to remove the epoxy resin that surrounds everything incase it is burnt and in need of repair? This is for a new design of particle accelerator using Heisenberg's Uncertainty Principle and particle confinement. I am posting from work on my Ipad so forgive me if the photo doesn't show up right away.

author: Psi
author_rank: Super Contributor
timestamp: June 08, 2013, 10:38:01 am
content: It's a neon sign transformer (NST)(well.. it looks identical to an NST. So 99.9% chance that's what it is).In any case it's high voltage output in the kV range. You can tell because of the ceramic terminal insulators.Input could be either 110VAC or 220VAC (50 or 60Hz)If you're not sure which try a large 150W mains voltage lighbulb inserieswith the primary.If it's a 110V NST and you shove in 220V the lightbulb will light up to ~50%+ brightness.If it the lightbulb stays off (or only glows really really dim) your voltage is ok and you can remove the lightbulb and connect it directly.Edit: Actually, sorry, don't do thatIt's a good method for checking most transformers but i'm a little worried with a NST you might damage the output isolation with too much output voltage. NST's are built to within 1inch of their life and too much output may arc over inside.The Safest plan is to feed it 110V first and see what the arc length is like. If the arcs look normal it's a 110V NST, if they're tiny it's probably designed for 220V.Output voltage will be somewhere between 7kV and 16kV across those two ceramic terminals (depending on specs). 10, 12 and 15kv are the most commonIt's highly likely that there's two transformers inside.The primary winding's are in parallel and the secondaries are connected in series with the center connected to the metal case.For example, it could output 12kV by having 6kV to case on each side.They do this because insulating 6kV to earth is easier/cheaper than insulating 12kV to earth.If it is a NST it will have a internal current limit between 20mA and 120mA (depending on specs)The current limit makes it safer than a microwave oven transformer (MOT)but an NST is still perfectly capably of killing you so be careful.It's possible that the NST you have died and was taken out of service so it will need checking.The normal failure mode is one side shorting out inside. (the other side usually still works so you still get half the volts from one side to case)

author: SeanB
author_rank: Super Contributor
timestamp: June 08, 2013, 01:33:08 pm
content: Neon transformer, so it probably has a 230V primary ( as it is in Australia) and will have an output of around 16kV. Take a length of bare steel wire and attach to the output terminals and have a grounded rod attached to the case so that each is 4mm away from the rod and at least 20mm away from the other. Power it and see if it arcs there, each side having a similar arc. Careful of the HT side, it at a minimum is incredibly painful, and just gets worse, the least you will get is a very bad point burn if you are too close, it can kill quite easily.To check current take a cheap $5 multimeter with a 10A AC range and connect it between the output terminals and power the meter on, then turn on the NST and read the AC current through the meter. If you get it wrong bye bye meter, so that is why you use a $5 meter. Short circuit current will be in the range of 20-200mA, depending on the transformer.Funny thing is that these draw a constant input power, as they have a ferroresonant circuit inside that provides the output. This is working as the epoxy fill is not cracked and burnt, as this is the failure mode, it lets the smoke out violently.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: June 08, 2013, 01:54:03 pm
content: if it's still working you should build one of these:http://youtu.be/R_AVmwKaMUs

author: don.r
author_rank: Frequent Contributor
timestamp: June 08, 2013, 03:04:20 pm
content: That would probably be 110V primary as E Metals is in Kent,Washington, USA.

author: SeanB
author_rank: Super Contributor
timestamp: June 08, 2013, 04:05:42 pm
content: Ok, but you know the old chestnut about forum profiles and getting the country right..........I did the quick and nasty Jacobs ladder, found out that the rods do get really hot, if I had left it on for more than about 2 minutes the brass brazing rods I used would probably have melted. As it was they got smoking hot, cleaned the oil film off them quite well on the one side.

author: Xsfacade
author_rank: Newbie
timestamp: June 09, 2013, 11:06:33 am
content: Thanks for all the great information. I would like to ask for recommendations on the correct transformer for a 1 to 3 million volt tesla coil type application?

author: Bloch
author_rank: Unknown
timestamp: June 09, 2013, 01:21:27 pm
content: Quote from: Xsfacade on June 09, 2013, 11:06:33 amThat kind of recommendations will be asked for then you grow out off the beginners topic

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: June 09, 2013, 01:40:42 pm
content: 3 million volt tesla coil shouldn't be too hard to build, plans for them are all over google.http://youtu.be/hgll-XTqcS4

author: Psi
author_rank: Super Contributor
timestamp: June 09, 2013, 01:49:07 pm
content: A typical sized tesla coil is around 0.3 -> 0.5MVThis one is probably around 3MV

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: June 09, 2013, 02:02:08 pm
content: Just make one twice this big:http://www.ke5fx.com/tesla.html

author: Psi
author_rank: Super Contributor
timestamp: June 09, 2013, 02:09:54 pm
content: That's a pretty bad design, there's no real top load on it and the primary coil wire is far to thin to carry the current that pole pig transformer can store in the capacitor bank.It's a shame really, because the secondary coil itself is nice and big and that pole pig could produce some monster sparks.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: June 09, 2013, 02:15:08 pm
content: I'm assuming that since the o.p. is working on his p.h.d. he'll be able to work out the bugs.I've built several smaller ones, they are fun to watch.

author: G7PSK
author_rank: Super Contributor
timestamp: June 09, 2013, 03:19:53 pm
content: This is what you really really want, go no admit it you know you want to.http://youtu.be/5Td--HItuoI