Toroidal Transformer Winding - Page 1
Forum section: electronics / projects

author: Puffie40
author_rank: Regular Contributor
timestamp: January 19, 2015, 02:20:38 am
content: Hey guys, first post here.I have been researching some high voltage power supplies for some night vision tubes and one circuit (http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Spezialroehren/XX1080/xx1080.pdf- The article is in dutch, but fig.1 is the circuit) requires I make a custom transformer for it.So it is a toroidal transformer with three windings on a 36x22 ferrite ring:6 loops 0.35mm (Primary)3 loops 0.25mm (Primary)1500 loops 0.1mm (Secondary) (... I might have an idea on how to do this one)from what I skimmed off the internet, it seems to me the procedure to build one is to put the primary windings on first, then the secondary windings. Since the secondary has so many windings, I believe I should go the other way around.has anyone had any experience making a toroidal transformer? What advice can you give? Should I consider some form of insulation tape between layers?

author: radiomog
author_rank: Regular Contributor
timestamp: January 19, 2015, 02:52:43 am
content: I've wound many one, sometimes 2 wire units, but 1500 turns? dang!, not that many, typically less than 50.. so I'm "in" out of curiosity!

author: Puffie40
author_rank: Regular Contributor
timestamp: January 19, 2015, 06:36:46 am
content: Quote from: 3roomlab on January 19, 2015, 03:27:53 amIts a light amplification (night vision) tube. Both the infrared converter tubes (Gen. 0) and the Gen. 1 tubes require around 15 kilovolts to operate (Not sure if newer generations used less voltage) and the power supplies typically are simple power inverters and multipliers. As far as my research goes, I don't believe the tubes actually consume much current.I should probably ask sooner or later over in Test Equipment how I'm going to measure the output voltage - it is well out of the range of any equipment I have.

author: MK
author_rank: Regular Contributor
timestamp: January 19, 2015, 07:23:33 am
content: The tubes themselves consume almost no current, but the dynode resistor chain does take some current, depends upon the max signal you expect to see, you can scale back the resistor chain current, but then you get worse linearity at higher light levels.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 19, 2015, 08:45:11 am
content: Why not use an FBT?A few of those won't be very good as toroidial, because of the very high stray capacitance of that construction method.Bank wound windings are more typical for high voltages, as the capacitance is lower. Resonant circuits (whether with full on controllers, or just plain old oscillators) are still pretty much required, especially as voltage goes up more and more.Tim

author: Chris Jones
author_rank: Regular Contributor
timestamp: January 19, 2015, 01:02:43 pm
content: Have a look on youtube for toroidal coil winders.They are pretty clever machines! Unless you buy or build one of these, you might be better off with a ferrite core that comes in two halves with a cylindrical former, for example an ETD, RM, UI or pot core. Even for a cylindrical coil former it would be nice to have a tension regulating mechanism for the winder, like this one:

author: penfold
author_rank: Frequent Contributor
timestamp: January 19, 2015, 11:51:17 pm
content: There's a time and a place for toroids, they don't behave particularly well with high voltages. Unless there's some serious EMI problems then just stick with something like an E core, maybe a U perhaps. A form that is taller than wide will let you achieve lower inter-winding capacitance which at high voltage and appreciably high frequency will cause you enough problems.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 20, 2015, 12:34:09 am
content: Wow, I don't think it would be worth gearing up to do 1500 turn windings just to produce ONE transformer.I would investigate using a couple or three of these and a Cockcroft-Walton multiplier circuit...http://www.goldmine-elec-products.com/prodinfo.asp?number=G13599http://www.allaboutcircuits.com/vol_3/chpt_3/8.html

author: Puffie40
author_rank: Regular Contributor
timestamp: January 20, 2015, 07:01:02 am
content: Quote from: penfold on January 19, 2015, 11:51:17 pmThats a good point, Right now I'm going with what that dutch article described (Translation below), and I'm all for redesigning the transformer if it means I can use a bobbin-style, which means simpler tooling. Is there any references you can recommend for transformer design?working backwards from the multiplier, I get 15kV/8 Diodes = 1875V, for a transformer ratio of 1:156.25. The one part I don't understand about the circuit is the requirement for two primary windings.Quote from: Translation of dutch circuit description via Google translate

author: tautech
author_rank: Super Contributor
timestamp: January 20, 2015, 07:20:37 am
content: n2 is the feedback winding and is required.QuoteSave this link for future reference.There are links within the page also.http://ludens.cl/Electron/trafos/trafos.html

author: coppice
author_rank: Super Contributor
timestamp: January 20, 2015, 07:52:32 am
content: Quote from: Chris Jones on January 19, 2015, 01:02:43 pmI wondered for years how you assemble toroidal transformers at a practical speed for high volume production. Then I spent some time in a plant with lines of those machines, making millions of current transformers per annum. They are clever machines, and fascinating to watch, but they do take an awful long time to wind, and it takes quite a lot of staff to run them. Its really quite a clumsy process, and we only get 30 cent CTs if the labour is very cheap.