Transformer insulateing tape?
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From: Perenis on 20 Jun 2010 14:59 On Sun, 20 Jun 2010 14:06:54 -0400, Hammy <spam(a)spam.com> wrote: > >>That said, I have wound a TV hor output transformer with normal A4 paper as isolation. >>As long as temperature stays low, and it does not get wet, it works. Only up to about 1000V isolation (that's generous). Without impregnation, that paper looks like it is not even there to the excited electron. Even through several layers of it. D'oh!
From: Perenis on 20 Jun 2010 15:00 On Sun, 20 Jun 2010 14:06:54 -0400, Hammy <spam(a)spam.com> wrote: >>I am not sure if you can get Melinex in low quantities. >> >I'm going to check a couple of motor rewind shops in town see if they >have the tape But thanks for the suggestion. Much easier to find the current common item, DuPont NOMEX insulating paper.
From: Perenis on 20 Jun 2010 15:02 On Sun, 20 Jun 2010 11:09:26 -0700, qrk <SpamTrap(a)spam.net> wrote: >Look on eBay, you can find people selling transformer tape for cheap. Jeez. I have been away from ebay so long I never even gave it a thought, but OF COURSE!
From: Jan Panteltje on 20 Jun 2010 15:05 On a sunny day (Sun, 20 Jun 2010 11:59:21 -0700) it happened Perenis <Perenis(a)hereforlongtime.org> wrote in <85ps169h4p5qbdcnk77le8j5vg1qk48dpe(a)4ax.com>: >On Sun, 20 Jun 2010 14:06:54 -0400, Hammy <spam(a)spam.com> wrote: > >> >>>That said, I have wound a TV hor output transformer with normal A4 paper as isolation. >>>As long as temperature stays low, and it does not get wet, it works. > > Only up to about 1000V isolation (that's generous). Without >impregnation, that paper looks like it is not even there to the excited >electron. Even through several layers of it. D'oh! Sure, but how much voltage you have between layers if you wind in a normal way is something you can calculate. 1000 V is a lot, much more then was dealing with. Say if you have 1 turn per volt, for arguments sake, and 100 turns per layer, 3 layers, then there is no problem. IIRC I used about 1 turn per volt 440 turns for the H scan coil drive winding Long time ago, BW TV, my school days, tubes, worked nicely.
From: Perenis on 20 Jun 2010 15:06
On Sun, 20 Jun 2010 11:21:35 -0700, qrk <SpamTrap(a)spam.net> wrote: >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. True, all but for heat considerations that cause me to lean toward the high side of any such window. Sort of like the buffer we use in selecting a cap voltage for a design. |