1kV AC - Page 1
Forum section: electronics / beginners

author: jwbrooks
author_rank: Contributor
timestamp: December 19, 2013, 06:49:44 pm
content: ObjectiveI need 1kV AC at 60Hz. There should "theoretically" be no current because there is no load. (I think)RequirementsI need to energize two electrodes to a voltage around 1000VAC (anywhere b/w 600 to 2000 would be fine). The oscillations need to be centered around ground.Previous workI worked on this a while back. First, I tried using a 10to100V (ish) transformer and wired 120V up to the primary. I figured that since I didn't have a load that it shouldn't matter. It didn't work. This was two years ago (so I've forgotten a lot of what I did), and I didn't know electronics very well at all (still learning).Finally, I ended up using a ~$100 120VAC to 800VAC power transformer. It worked, but it was expensive.I've also wondered about using microwave transformers, but I've read scary things about them and would prefer something easier if possible.The QuestionlIs there a cheap(er) way to produce this voltage?

author: Rerouter
author_rank: Super Contributor
timestamp: December 19, 2013, 07:42:44 pm
content: cheapest soultion i can come up with is a $25 neon sign 10KV transformer fed from a 120:16 step down or similar (equally cheap) transformeras quite a few neon transformers come with a center tap

author: jwbrooks
author_rank: Contributor
timestamp: December 19, 2013, 07:54:41 pm
content: I'm not trying to be picky, but I'd prefer to have a single transformer if possible. I guess I'm looking for cheap and simple. Maybe too much?Thanks for your suggestion.

author: ConKbot
author_rank: Super Contributor
timestamp: December 19, 2013, 09:29:48 pm
content: Hammond mfg has factory stock ofhttp://www.digikey.com/product-detail/en/714/714HM-ND/4555461020V, CT, 170mA, 180VA. At $75 each, not cheap, not horrifically expensive.Now that I think of it, 1 kv, center tapped is actually quite a PITA voltage to get. Its a high enough voltage its not commonly used, low enough that all your usually high voltage stuff is greatly above it. All the stuff that would run in that range is generally high frequency. The only possibly cheaper solution I can think of is 2x 460/480v or 575v control transformers put in series, run backwards.

author: Psi
author_rank: Super Contributor
timestamp: December 19, 2013, 11:06:55 pm
content: Could always rewind an existing transformer.Would have to add some insulation between the layers though, 1kV is high enough to break down standard enameled wire

author: notsob
author_rank: Frequent Contributor
timestamp: December 19, 2013, 11:28:44 pm
content: As a suggestion, go to a car wrecking yard and get a couple of 2nd hand ignition coils, much higher voltage, but you may be able to open them and remove a lot of the HV side to suit what you wantbe aware this uses pulsed 12VDC input so you would need to provide your own 60Hz input at 12V

author: AlfBaz
author_rank: Super Contributor
timestamp: December 19, 2013, 11:44:56 pm
content: I don't know what voltages coal mines use in the US but here in oz they're mostly all 1000V to keep the size of trailing cables down. Nearly any scrap electrical equipment from this industry should have 1000V to 110/120V control transformer. Since you're not pulling any current simply use the secondary (120) as the primaryEdit: on second thoughts I doubt the 1000v side will be centre tapped

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2013, 12:20:08 am
content: An oil burner ignition transformer is probably the closest to what you need - may need to reduce voltage though as output is likely to be a few kV- maybe run it on 24-48VAC from another transformer.Microwave oven transformer cheapest, but dangerous due to lack of current limiting. However if your output current requirement is small, you could use resistive or inductive current-limiting on the primary to reduce the hazard. However i suspect a cheap MOT probably runs partially in saturation, so this may not work well.

author: IanB
author_rank: Super Contributor
timestamp: December 20, 2013, 12:33:13 am
content: What about a transformer designed for the h.t. supply of vacuum tube circuits? I had lots of salvaged transformers from old vacuum tube equipment with h.t. windings producing something like 600 V as I recall. Presumably you could get a modern transformer designed for the same purpose if you can't find any old ones? I'm not sure if they would be center tapped, but if not you could perhaps put two such transformers in series.

author: codeboy2k
author_rank: Super Contributor
timestamp: December 20, 2013, 01:55:10 am
content: Quote from: jwbrooks on December 19, 2013, 06:49:44 pmI'll play the devil's advocate here, and ask you why you think there will be no current ?You said "no load", and "no load" implies "no current" .... I say NO WORK DONE. Now, why do you want a transformer that produces 1kV but does no work ?? Surely you want it to dosomething??

author: Anks
author_rank: Frequent Contributor
timestamp: December 20, 2013, 02:19:04 am
content: I wound a 950v transformer recently on my own lathe so it cant be hard if you take the former to a winders and ask them to do the winding. The hard bit is dismantling the old transformer.Also why have a transformer that dose nothing!

author: Macbeth
author_rank: Super Contributor
timestamp: December 20, 2013, 05:30:08 am
content: Quote from: Anks on December 20, 2013, 02:19:04 amI like this - also, that set-up is a faceplate and "dog"? - my mini lathe only has a 4 jaw chuck and dead centre. I take it you use the auto feed to wind the wire and keep an eye on it to reverse it at the right end points? I want to wind my own transformers now!

author: 300EVIL
author_rank: Contributor
timestamp: December 20, 2013, 07:08:08 am
content: A "Bug Zapper" transformer will get you really close to what your looking for....

author: SeanB
author_rank: Super Contributor
timestamp: December 20, 2013, 05:30:10 pm
content: If you are going to wind a transformer you will need to have a layer of insulating kapton sheet covering each completed layer of winding, along with a gap at the ends so that it will not flash over. Typically you will wind for 50-100V per layer, so to get to the 1kv centre tapped one you want that will be between 20 to 40 layers of windings with kapton tape cover. Needs a big core, and as the primary will be wound below it the leadouts will need to be insulated for 2kV fro them as well, along with at least 5 layers of Kapton tape as winding separator between primary and secondary. If you really need equal capacitance windings then you will need to split the windings so each half is wound at the same time on just under half the core width, with a spacer tape applied to each layer to keep the tape layer flat. Those are a PITA to wind, I have done some for other voltages that are lower, and they take a day or more to get done properly, as you are going slow and with 2 spools with a lot of stopping for tape and tie down..

author: Anks
author_rank: Frequent Contributor
timestamp: December 20, 2013, 06:52:27 pm
content: Quote from: Macbeth on December 20, 2013, 05:30:08 amIt would be easier with a chuck Id imagine. the feed was done with a old hacked printer and micro to control the stepper.here is a pic of the setupI second SeanB about making sure you use insulation but I used thin wire as I only needed a small amount of current.

author: SeanB
author_rank: Super Contributor
timestamp: December 20, 2013, 07:29:47 pm
content: I took apart an electric fence energiser that had this construction where the failure was that the outer layer arced over ( was a bloody pain literally to unpot the transformer from the GRP resin they filled the housing with) at the point where the sleeving they used was next to another wire. That killed the unit, it still made voltage but it was not the 10kV needed for the fence, more like 1kV or less with the internal arcing. Drive was a 30uf capacitor charged to 300v discharged by a really beefy TRIAC, with the thin wire providing current limiting along with the ESR of the poor film capacitor.

author: jwbrooks
author_rank: Contributor
timestamp: December 20, 2013, 08:15:58 pm
content: I like these ideas. I'm going to have to look into the bug zapper transformer. Unfortunately, it doesn't seem to be a very common thing to sell on ebay.To answer the other questions, there is no official load because I'm using these as electrodes. I'm planning on making a Paul trap (a type of ion trap), and trapping small charged particles (like corn starch).

author: 300EVIL
author_rank: Contributor
timestamp: December 20, 2013, 10:34:35 pm
content: Quote from: jwbrooks on December 20, 2013, 08:15:58 pmI'd look on craigslist for a used one. I find them next to garbage cans all the time. Almost a regular staple at garage sales.

author: TheBay
author_rank: Unknown
timestamp: December 21, 2013, 02:27:12 am
content: Find a cheap fluorescent camping light