[TCML] Inductor design program?
jhowson4 at comcast.net
jhowson4 at comcast.net
Fri Apr 23 07:17:32 MDT 2010
Your site is very nice and informative, And of course tells me exactly the information I wanted to know.
Now here is a question, how would one do this for a variac? The same way. or would a modification be made?
ps. GNU plot rocks, glad to see some one else using it!
John "Jay" Howson IV
----- Original Message -----
From: "David Dean" <deano at deanostoybox.com>
To: "Tesla Coil Mailing List" <tesla at pupman.com>
Sent: Friday, April 23, 2010 12:00:44 AM GMT -05:00 US/Canada Eastern
Subject: Re: [TCML] Inductor design program?
Sorry the page is not done, only graphs there. Lots of projects, nothing ever
First up is a V /I plot for the "rough and ready ballast" which consists of two
MOT primaries on a single MOT core, primaries in series. The non-linearity in
the curves is due to core saturation.
Next is a V/I plot for a 15/30 NST with the secondaries shorted compared to the
"rough and ready" ballast using both one and two primaries at 120V (0-130).
Note the linearity of the ballast is better than the NST when both primaries are
in series keeping the core out of saturation. (more turns/volt)
Next is a saturation curve for the 3.5 square inch MOT core used in the
Next is a saturation curve for the "double wide" MOT core (two identical cores
combined into a single wider one) with 7 square inch core area.
These curves were done with ten turns of #10 AWG THHN. Current is vertical,
voltage horizontal. From this it can be seen how many turns per volt are needed
to stay out of core saturation. The curve starts to turn up at 16V, (double wide
core) so I need 1.6 turns/volt to keep the ballast linear. For operation at
240V that is 384 turns, more or less.
The next graph is the V/I plot for the finished "double wide core" ballast made
from two identical MOT cores and wound with #11 AWG 200 C magnet wire. Forgive
me, I did this last July and do not remember how many turns I was able to stuff
into the winding window (not enough), but just enough to keep linearity up to
240V, saturation starts there. It is still more linear than a NST, so serves my
The last graph is just a plot of the inductive reactance vs gap thickness
(plastic spacers, mostly thin sheets of GPO3) but you need to use your
imagination to "smooth" the curve between the points. GNU Plot or whatever
application I used to make the graphs seemed to lack a "smoothing" feature.
Hope this helps some.
On Thursday 22 April 2010 09:37:39 pm jhowson4 at comcast.net wrote:
> Thanks Scott, DC, and other contributors,
> I guess I shall start out by winding a 140 turn #10 inductor for 30 Amp
> service. I will tap each layer. then I will gap the core until one of the
> combination's gives me the desired current draw.
> I take it I would be graphing Voltage vrs Current? and the slope is
> inductance? or is it Current Vrs Voltage.
> John "Jay" Howson IV
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