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Re: Homemade Trasformer
Yes, it will work, after a fashion. There was someone on the list (or
perhaps the HV list) who made cores from iron filings (scrap from on a
machine shop) and glue or resin.
The packing density (how much iron cross section there is in a given core
cross sectional area) of flat laminations is higher than rods, but this is
mostly a physical size issue, of great concern to commercial manufacturers,
but not necessarily to you.
The larger core cross section area means the windings will be a bit longer
(in terms of feet of wire) than they would be on a nice compact rectangular
core, which will raise your IR losses slightly (again, probably not an
issue).
The physically larger size means that the leakage inductance (that part of
the field that doesn't go through both windings) will be slightly higher.
Again, not an issue for you.
Probably the most challenging thing will be finding suitable silicon steel
rods (i.e transformer iron). Soft iron would work, but saturates at a
lower flux than steel. Silicon steel is nice and high resistance (reduces
eddy current losses).
Remember that you want the "magnetic circuit" to have the minimum air (or
non iron) gap possible. This is why the varnish on commercial transformers
is just thick enough to provide electrical insulation (for eddy currents).
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> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Homemade Trasformer
> Date: Sunday, February 13, 2000 4:31 AM
>
> Original Poster: ross andrews <sflourine-at-home-dot-com>
>
>
>
> Hi all,
>
> --This is prolly about the thousanth time this has come up on the list,
> but a few more posts can't hurt--
>
> I am thinking of building my own transformer for my coil - not that I
> belive it'll be close to as good as a pig, but want to do it myself
> (yeah, i'm nuts). I found dad's old EE book and ran the numbers, and I
> should only need 120 turns in the primary to choke the 240V/60hz mains
> current (as long as the core is bigger then 14 in^2), and 6000 or so
> turns in the secondary to give 12 kV. So far, I have found that the
> biggest problem is the core -- I don't think it can just be a piece of
> barstock b/c it seems like it will saturate really easily -- is this
> right? Also, eddy current and hysterysis (spelled wrong) are less in a
> laminated core, so I pulled this out of my shorts: How about using many
> small metal "dowels" and coating them with a sealer of some sort (will
> polyurethane stick to metal??), then sticking them all together. What
> you have now is a neat little bundle of rods - wrap the primary and
> secondary, then bend the whole mess around a garbage can to form a
> toroidal shaped tranny. It seems like this should work. Will it?
>
> Any comments apprecited.
>
> Thanks,
>
> Ross
>
>