Jim,
What you want to do is perfectly feasible, and is something that I will be
doing myself shortly in connection with a big DC coil project.
Only yesterday I was watching the video from 'RogerInOhio' showing his
inductor build
https://www.youtube.com/watch?v=l-tEBkAbEms&list=UULBfVcp-QpjmET3ecVIP1Zw ,
and he achieved a higher inductance value than what you require, but on a
smaller core size.
I have already wound both a DIY mini-pig and an inductor before, the
mini-pig being under oil, while the inductor was for my LV ballast, so
insulation was not such an issue with the latter. But regardless of whether
you will be using oil, I would now advise using the correct HV tape between
layers, which is what I will be doing next time, and also if possible using
a lathe rather than turning by hand.
I fortunately have a lathe (so in case you do) my method was that I made
formers up (from Tufnol sheet) that were a sliding fit over the actual metal
core. I then made a wooden block the same size as the metal core and gripped
this in the lathe chuck. The earlier Tufnol former I had made then slipped
over the wooden block held in the lathe. Once wound, you then slip the whole
former complete with its newly wound windings off the wooden block, and
slide it onto the actual transformer core.
A good method is to try and use the automatic feed of the lathe to space the
winding automatically. It does need some careful maths, but if you know from
the chosen wire diameter, that you would get [say] 100 turns a layer, then
work out the nearest feed rate of the lathe that will supply that figure
(wire diam' = per turn of screw). Then if necessary even by choosing a wire
diameter next size up or down, it #may# be possible to get a fairly close
match.
If you feed the wire through a makeshift holder attached to the top slide,
it's possible to tweak the slide's position whilst running to compensate for
any discrepancy in the ratios, a technique I have used successfully when
winding an 8 inch coil.
Video of my winding here: https://www.youtube.com/watch?v=VTqRahADgds
(This was on the LV side, so brown paper and varnish sufficed)
Phil
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Jim Mora
Sent: 26 July 2014 13:16
To: 'Tesla Coil Mailing List'
Subject: [TCML] FW: Charging Inductor construction choices- Plain text
sorry.
________________________________________
From: Jim Mora [mailto:wavetuner@xxxxxxxxx]
Sent: Saturday, July 26, 2014 5:14 AM
To: 'Tesla Coil Mailing List'
Subject: Charging Inductor construction choices.
Hello Friends,
I am considering winding my own DC charging inductors. Yea that will be a
major effort but we are pretty good at winding things. I have several core
candidates and would go on the scrap hunt if they don?t make the cut. The
one presently in front of me (or and IE leaves). Came form a 4KV 3P Plate
transformer that had a shorted primary turn ? an eBay buy. I scrapped the
copper and pulled all the leaves so it is a true EI which is good as the air
gap could be visually adjusted. It has nicely placed bolt holes. It was 4
to 5 inches thick and has three cores of course. Roughly >1 + 3/4 by 4.5
inches tall. The winding windows are typical stamped E cores. So 4.5x1 and
3/4 or 13 /16 to be more precise. I see my options to cut out the center I
giving me a huge winding window for 2 coils or cut off an L and have narrow
deep window which probably would have less losses. These would be 4 to 5
inch oblong coils and tight DIY fit.
The specs I want to achieve is two coils preferably on one core able to
handle up to 750 ma and 25KV so maybe I should be looking at a mini pole pig
core. I like the EI conception rather than C core where the gaps are
generally hidden and require strapping. Having a threaded gap adjustment
would be cool. I have a huge EI HV transformer with many taps which must
have be a radar transformer. I find it a bit scary. I used a low ohm meter
to connect out all the taps the best I could figure. The core is like 12?
across, it may be 24 inches wide from memory and maybe 18? high. Copper is
so high now I have considered taking this one down. It weighs in very heavy!
This is a single phase core. I could make the stack any desired size thick.
Ample room for neat DIY HV standoff.
Opinions anyone?
I assume the Inductors should have a high Q for top charging profiles?
Thanks,
Jim Mora
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