Building a transformer
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From: ArameFarpado on 8 Aug 2006 20:12 Forgot one detail: first rool the primary coil them put a plastic or corse paper strip to isolate the 2 coils then rool the secundary coil
From: Rich Grise on 8 Aug 2006 20:14 On Tue, 08 Aug 2006 13:21:34 -0700, zekor wrote: > Mark Fortune wrote: >> Greetings to the collective. >> >> For my next project I want to build a bench power supply and do away >> with this old switch mode AT computer PSU that i'm currently using. >> >> The design I have in mind will be pretty beefy, giving a wide range of >> fixed and variable output voltages (i'm thinking from -50v up to +50) >> and deliver up to 5amps of current. if my estimates are right i'll need >> a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've >> had a look at some transformers in this range, and they're a little out >> of my price range. so now i'm considering building my own. >> >> The specifications I need are as follows: >> >> primary: 0-230v @ 50Hz >> Secondary: 60v-0-60v >> secondary output current max: 5A >> >> I have an intermediate understanding of transformers, but have never >> actually built one, hence I am seeking advice from those with experience >> in this field. >> So where do I start? what type of core is best for this application? - I >> have a friend who's blasting off that toroids are best, but i'd like a >> second opinion, and what kind of wire to use for the primary and >> secondaries? what are good safety practices regarding insulation? Is >> this even a feasable project to undertake (moreso on the money side than >> timewise). Any other advice also greatly appreciated. > > I would recommend reading up from every source. I have built torroids > using the winding which was orginally a variac. These were 110 volt > units. You automatically have a primary so all you need to do is wind > the secondaries on top. I have also done the other type of transformer, > schelacing.the iron plates. I would also recomend what others have, buy > surplus on the market. Combine transformers if you can't find them. > I used to work for a battery charger manufacturer who made their own transformers. They had a machine to stack the lams, alternating, of course, and a big machine to spin the bobbin while the guy hand-wound the windings on it. Then, when it was all stacked, they'd whack it to make sure all of the lams were as tight as they could get them, bolt it up, hypot it, and then bake them and dip them in hot varnish. BTW, I don't think there are many USENETizens who would consider themselves part of any "collective" - that's the Borg. =:-O Good Luck! Rich
From: ArameFarpado on 8 Aug 2006 20:19 ArameFarpado wrote: > this will be a 600Watt transformer > > you will need iron of 150mm EEE and III (a standard dimension) > a form of 50x54mm > > primary: > use 1.35mm diameter wire > roll 377 spirals > > secondary: > use wire of 1.77mm diameter (if this does not exist, get the after next in > diameter) > weld first out line (60v) > roll 104 spirals > weld second out line (0v) > roll 104 spirals > weld third out line (60v) > > > put the irons one by one always alternate positions > tight as much as you can the irons > dive it into hot varnish and let it dry > > this is just the transformer, i guess you will also want to pass AC to DC > and maybe a voltage regulator controlled by a variable resistor, but that > is another story ;) > > > regards > ArameFarpado Forgot one detail: first rool the primary coil them put a plastic or corse paper strip to isolate the 2 coils then rool the secundary coil
From: Father Haskell on 8 Aug 2006 20:23 Tim Wescott wrote: > Jim Thompson wrote: > > On Tue, 08 Aug 2006 21:19:21 GMT, "ian field" <dai.ode(a)ntlworld.com> > > wrote: > > > > > >>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in > >>message news:99uhd21d83biuj4122hfrv1p47k4gip41h(a)4ax.com... > >> > >>>On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)" > >>><jim(a)rstengineering.com> wrote: > >>> > >>> > >>>>What primitive semiconductors did you use in the output stage, or was it a > >>>>toob device? Did we have 2N3055s in '75? I don't memember. > >>>> > >>>>Jim > >>>> > >>> > >>>[snip] > >>> > >>>I'm trying to remember what semiconductors I used. But, IIRC, > >>>2N3055's *were* available around that time. > >>> > >>> ...Jim Thompson > >>>-- > >>>| James E.Thompson, P.E. | mens | > >>>| Analog Innovations, Inc. | et | > >>>| Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > >>>| Phoenix, Arizona Voice:(480)460-2350 | | > >>>| E-mail Address at Website Fax:(480)460-2142 | Brass Rat | > >>>| http://www.analog-innovations.com | 1962 | > >>> > >>>I love to cook with wine. Sometimes I even put it in the food. > >> > >>Was it Ge or Si ? > >> > > > > > > It was Silicon. I didn't use any Germanium power devices since I > > boosted my car radio back when I was a junior in high school. > > > > ...Jim Thompson > > Correction: it _is_ silicon. > http://www.onsemi.com/pub/Collateral/2N3055-D.PDF. > > Digi-Key has them for $2.10 a pop, in the TO-3 case, no less. 2N3055s are as common as 2N2222s. Salvage them from junked supplies or amps, and the cost is nothing.
From: Rich Grise on 8 Aug 2006 21:00
On Tue, 08 Aug 2006 22:53:34 +0100, John Woodgate wrote: > In message <Uf7Cg.6098$vl5.3392(a)newsfe4-win.ntli.net>, dated Tue, 8 Aug > 2006, ian field <dai.ode(a)ntlworld.com> writes >>You can't beat a microwave oven transformer with a secondary >>transplant! > > That depends on how the leakage inductance is produced, and whether you > can remove it, which you must in order to use it as a conventional > transformer Taking out the old secondary is almost trivial, with a hacksaw and a chisel. ;-) But apparenlty, you need to add windings to the primary to bring the magnetizing current down, or somethiing like that. I have an old MOT that I've been experimenting with, and the idling current is just way too much for any self-respecting 60 Hz trannie, albeit they do have to account for the shunts, which current-limit the output. On and off, I've been poking around with this thing, but now I'm at a crossroads with it - do I cut it open, take the bobbin out, and enhance the primary that way, or do I thread more #18 Formvar wire through it until I build up another layer of windings? So far, threading the new wire through has turned out to be much more of a PITA than I had expected, so it's kind of on the back burner for the moment. Good Luck! Rich |