Transformer insulateing tape?
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From: qrk on 20 Jun 2010 14:21 On Sun, 20 Jun 2010 13:35:55 -0400, Hammy <spam(a)spam.com> wrote: [major snippage] > >> If there is bobbin space, I would do things like switching to say 3 x >>#28 if it fits. Or two flat wound. > >I'm limited by what's available I have 22AWG, 26AWG and 30AWG. I've >mainly used the 26AWG. I think once you get larger then 26AWG skin >effect becomes a problem. Mind you I have coil craft flyback >transformers with what looks like at least Parallel 21AWG secondaries. > >I can and have gotten heavier gauge magnet wire from some rewind shops >in town and actually I'll check if he's got the tape on Monday. > >> He gave a lot of info, but there were still a couple details to talk >>about. You're up against proximity effect which will be more prevalent than skin effect. "Soft Ferrites" by E.C. Snelling covers proximity effect. If you have an university nearby, they usually carry this book. There is an optimal wire diameter to use, but there is around a 2 AWG variation from the optimal size which will work well in practice. -- Mark
From: Archimedes' Lever on 20 Jun 2010 14:37 On Sun, 20 Jun 2010 13:35:55 -0400, Hammy <spam(a)spam.com> wrote: >Interleaving windings is a pretty common technique to reduce leakage >inductance and improve coupling there is a tradeoff it increases >interwinding capacitance. Yes, but interleaving does not mean what you or he thinks it means (apparently). You should start out placing the entire primary on top of the rest, and then dial that in, THEN place it at the base of the bobbin, and dial in the secondaries (again), THEN you can start working on optimization elements, though in your app it would entirely unnecessary. A would also look into a increase in the primary gauge choice.
From: Archimedes' Lever on 20 Jun 2010 14:43 On Sun, 20 Jun 2010 13:35:55 -0400, Hammy <spam(a)spam.com> wrote: > I think once you get larger then 26AWG skin >effect becomes a problem. Ok. I still think the current is high for that since a single #26 is only good for one amp. and it would take more than 3 #30 to get that. I would then jump to 4 x #30. If the turns count is low, you could simply place it in its entirety into a Teflon tube and forget about tape altogether.
From: Wimpie on 20 Jun 2010 14:53 On 20 jun, 18:29, Archimedes' Lever <OneBigLe...(a)InfiniteSeries.Org> wrote: > On Sun, 20 Jun 2010 05:24:54 -0700 (PDT), Wimpie <wimabc...(a)tetech.nl> > wrote: > > > > >On 20 jun, 13:40, Archimedes' Lever <OneBigLe...(a)InfiniteSeries.Org> > >wrote: > >> On Sun, 20 Jun 2010 04:19:37 -0700 (PDT), Wimpie <wimabc...(a)tetech.nl> > >> wrote: > > >> >On 19 jun, 18:50, Hammy <s...(a)spam.com> wrote: > >> >> What kind of tape can you use for insulation between primary to > >> >> secondary of flyback transformer. I know mass produced professional > >> >> designs use a 3M specialty tape. What I'm looking for is a tape I > >> >> could pick up at Staples or some office supply store or hardware > >> >> store. > > >> >> The vinyl electrical tape I can find is only rated for 600V and 80C > >> >> MAX TEMP. > > >> >> Is there a commonly available tape that is good for higher temp and > >> >> offers higher insulation? I've read of people using a mylar tape is > >> >> there a brand name ,type anyone could recommend? > > >> >> This is for a 90 - 140Vac input flyback. > > >> >Hello, > > >> >A flyback needs low spreading inductance (to avoid excessive loss in > >> >the snubber). You don't want large barrier between your windings. > >> >Don't trust hobby tape, but try to get polyimide tape (brand name > >> >Kapton). It isn't cheap, but does the job. > > >> >Best regards, > > >> >Wim > >> >PA3DJS > >> >www.tetech.nl > >> >without abc, PM will reach me > > >> Kapton is usually too thick and is cumbersome to wind with. the tapes > >> that have been suggested are the right tapes to use. Polyester tapes > >> will get the windings as close together as they can be. > > >Hello Archimedes' Lever, > > >I assumed that he needs the tape to separate primary and secondary > >windings only. For example: > > >First half of primary turns in a layer > > two/three layers tape for safety insulation > >complete secondary winding > > two/three layers tape for safety insulation > >second half of primary turns in the last layer. > > And why is it you wish to split the primary winding and place half > UNDER the secondary, and half OVER the secondary? Reducing leakage induction. > > >In such an arrangement, kapton / polyimide is not that difficult to > >use (from experience), > > Kapton is only feasible on larger form factors. If this is a small pot > core it will not be as easy to use kapton, and Kapton does not"sink in" > it stays flat, which defeats your original suggestion that they be nested > as tightly together as they can. Within my reach, I have 19mm wide tape (from Farnell or RScomponents). As he speaks of 50 W output, core size is not very small. As he don't need lots of the tape he can cut it by hand. > > The poly tape has just as good electrical resistance, and takes up far > less bobbin space. The stuff is just too inflexible for smaller > applications. I have used it on say a 1.5" dia pot core, but it only had > a few primary turns and they were inside a Teflon tube already and wound > flat, so the Kapton fell on top of it flat. I doubt he will get the same > winding profile with 3 x #30. > > > however I fully agree that suitable polyester > >tape can do the job (cheaper, easier to work with and easier to > >get). > > Not to mention the way the industry does it in nearly every case. > > > The reason for mentioning the polyimide was that he can be > >almost sure to have something that is OK. > > If the step up is not that much, he is sure to be OK with cheap xformer > tape too. > > > > >Before making final decision, he also has to find out the expected > >over voltage category and whether he requires single or double/ > >reinforced safety barrier in his transformer (as this also determines > >the required clearance and creepage distance). > > He mentioned 12V and 5V, so I do not think he is doing an HV > application, and he could probably get away with zero transformer tape > using simple double strength mag wire. Granted I would still separate > primary from secondary, but I doubt he needs to worry about creepage > distances in such a LV application. He is already isolated from the AC > line. He mentions it is line-powered, so you have to account for over voltages and whether single or double/reinforced insulation is requried, even when the output voltage is 5V. If Hammy doesn't have EN 60950, or 60065 at hand, he may search for ECMA-287. It can be downloaded free and gives good guidance on creepage, clearance, insulation requirements, etc. > > If there is bobbin space, I would do things like switching to say 3 x > #28 if it fits. Or two flat wound. > > He gave a lot of info, but there were still a couple details to talk > about. Best regards, Wim PA3DJS www.tetech.nl
From: Jan Panteltje on 20 Jun 2010 14:53
On a sunny day (Sun, 20 Jun 2010 13:22:14 -0400) it happened Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in <Q2sTn.104184$rE4.75513(a)newsfe15.iad>: >Jan Panteltje wrote: > >> On a sunny day (Sun, 20 Jun 2010 07:43:29 -0700 (PDT)) it happened Proteus IIV >> <proteusiiv(a)gmail.com> wrote in >> <8316ba75-68e0-4f76-96fd-04cbc92ddbb8(a)u26g2000yqu.googlegroups.com>: >> >> >>>I AM PROTEUS >> >> >> An other Apple user flips out. >> >> FYI Steve Jobs wil die one day. >No.... Well, if they keep replacing parts, when they get to the brain, he wont be him anymore. > > > |