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Re: [TCML] charging reactors
Hi,
Bart, I apparently seem using the same formula as the guy on
http://www.pronine.ca/multind.htm
The formula seems to stem from the radio amateurs handbook. I took mine
from:
ARRL Handbook 1957 / p27
a=avg.diameter in inches = (Di+Da)/2
b=length of winding in inches
c=radial depth of winding in inches = (Da-Di)/2
L[uH]=(0.2*a^2*n^2)/(3*a+9*b+10*c)
I've verified it's results on my induction coils (without core, of course),
and it works well, i.e.:
My 26k turns induction coil secondary: measured 15.15H; calc. 15.09H; Error
0.42%
My 48k turns induction coil secondary: measured 49.8 H; calc. 47.7 H;
Error 4.22%
More precise methods could probably been taken from NBS circular 74, but the
above is about within the precision of my LCR meter.
For Jim's charging inductor I have the following proposals:
1.) Inductor 10H / 20kV / 1A, as an "air core" inductor:
--------------------------------------------------------
10 Pies à:
Inner diameter of winding: 100mm
Outer diameter of winding: 168mm
Width of winding (netto): 12mm
Width of pie (insulated): 17mm
Inner diameter of insulating sheets between pies: 85mm
Outer diameter of insulating sheets between pies: 180mm
Wire diameter (copper): 0.5mm (AWG 24)
Wire diameter (double. ins.) 0.566mm
Turns per pie: 1274
Total inductor:
No. of turns: 12740
Outer diameter: 180mm
Length of inductor: 170mm
Copper weight: 9.4kg
Inductance: 10.09H
Resistance: 488 ohm
1.) Inductor 10H / 20kV / 1A, as an "air core" inductor:
--------------------------------------------------------
6 Pies as above!
Total inductor:
No. of turns: 7641
Outer diameter: 180mm
Length of inductor: 102mm
Copper weight: 5.64kg
Inductance: 4.97H
Resistance: 293 ohm
I "think" an air-core inductor would be appropriate to Jim's application?
Well, the beast is big, but it'd be manageable. Advantage would be the
~constant L with rising current. When trying to size an iron core inductor,
I'm getting in trouble about saturation (yes, we sometimes operate our
induction coils into saturation; despite the stright cylinder core!). When
entering the values 20kV/1A (20kVA!) to a transformer design spreadsheet,
I'm getting huge cores, in the 100kg weight range. Or am I missing something
here?
I didn't convert metric to US-American units, 'cause I seem to remember Jim
to be used to SI ;-)
Best regards
Kurt
----- Original Message -----
From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Friday, March 06, 2009 3:59 AM
Subject: Re: [TCML] charging reactors
Tesla, well, would have been stuck with cotton covered wire. But if he had
access to todays magnet wire, probably small and compact as possible.
Interesting inductance script. However, either my calc's are wrong or the
script calc's are wrong for the inductance.
For multilayer, I'm using the following:
LuH = (31.6 x n^2 x ri^2) / (6 x ri + 9 x L + 10 x (ro-ri))
n = total turns
ri = inside coil radius
ro = outside coil radius
L = coil length
(all in meters)
Quite a discrepancy between the script inductance result and the above.
For the calculators inputs at 5H, he realizes 51.18 layers. If I use 24
awg (.0213" in his code) and adjust my layers the same, everything works
out fine (id, od, dcr, turns, wire length, etc..) except I show 1.75H
where he shows 5H (2"D, 4.75"L, 24G). Somethings odd here... and can't put
my finger on it.
Anyone else have a known working multilayer calculation for L?
Take care,
Bart
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