RE: General Coil Design

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Thomas <tom-at-pwrcom-dot-com.au> 


 > Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au>
 >

- sounds good so far-

 > Now you have my history, comes my question.  Secondary coil design.  I
 > originally thought 1mm enamelled copper.  About 750 turns on
 > 200mm form.
 > 160kHz resonant frequency.  I thought this would give me some
 > headroom if I
 > decide to get a pig later.  Got these design specs from a
 > coil on Herb's
 > tesla Page for a similarly powered transformer.  Then I spoke
 > to Claude,
 > also here in Sydney, and an experienced coiler, whom suggested that my
 > selection for copper was too thick, and turns too few.  He
 > suggested that I
 > choose 0.6mm copper and go for 1000-1200 turns on a 6 inch
 > former for a
 > secondary length of 30-32 inches.  I have plugged these
 > figures into JavaTC
 > and cannot for the life of me get the results I am expecting.  The
 > calculated resonant frequency is below 100kHz, which can't be right.
 >

I have a 750t (20AWG) 150mm diameter secondary that gives ~950mm streamers
from an 880VA NST.

I have not yet wound a 1000t secondary to compare the output, and probably
wont for quite some time, as this set up is working extremely well.

I'd be more worried about the 3.5:1 height to diameter ratio, and the 1.5m
JAVATC predicted spark length.

Make the coil taller or you will get many strikes to the primary coil/strike
rail. Best way to do that would be wind about 1000t of 20AWG on your 200mm
former to give a height of 920mm (4.6:1).

Here's a Javatc o/p I did that gave ~150kHz for your initial set up (made
many assumptions though):

J A V A T C v.10 - CONSOLIDATED OUTPUT
Tuesday, 9 December 2003 13:47:05

Units = meters

----------------------------------------------------
Surrounding Inputs:
1000 = Ground Plane Radius
0 = Wall Radius
0 = Wall Height
0 = Ceiling Radius
0 = Ceiling Height

----------------------------------------------------
Secondary Coil Inputs:
Current Profile = G.PROFILE_LOADED
0.1 = Radius 1
0.1 = Radius 2
0.5 = Height 1
1.185 = Height 2
750 = Turns
20 = Wire Awg

----------------------------------------------------
Primary Coil Inputs:
0.1275 = Radius 1
0.286 = Radius 2
0.5 = Height 1
0.5 = Height 2
7.92 = Turns
0.005 = Wire Diameter
0.0375 = Primary Cap (uF)
0 = Desired Coupling (k)

----------------------------------------------------
Top Load Object Inputs (dimensions & topload or ground connection):

Toroid #1: minor=0.24, major=0.8, height=1.3, topload

----------------------------------------------------
Secondary Outputs:
149.12 [kHz] = Secondary Resonant Frequency
90 [deg°] = Angle of Secondary
70.638 = Turns Per cm
0.01015 [cm] = Space Between Turns (edge to edge)
18 [awg] = Recommended Wire Size
471.239 [meters] = Length of Wire
3.43 = H/D Aspect Ratio
15.7 [ohms] = DC Resistance
27268 [ohms] = Reactance at Resonance
2.17 [kg] = Weight of Wire
29.103 [mH] = Les-Effective Series Inductance
29.581 [mH] = Lee-Equivalent Energy Inductance
28.772 [mH] = Ldc-Low Frequency Inductance
39.141 [pF] = Ces-Effective Shunt Capacitance
38.279 [pF] = Cee-Equivalent Energy Capacitance
58.932 [pF] = Cdc-Low Frequency Capacitance
0.171 [mm] = Skin Depth
33.537 [pF] = Topload Effective Capacitance

----------------------------------------------------
Primary Outputs:
149.12 [kHz] = Primary Resonant Frequency
0 [%] = Percent Detuned
0 [deg°] = Angle of Primary
10.282 [meters] = Length of Wire
1.5 [cm] = Average spacing between turns (edge to edge)
2.75 [cm] = Primary to Secondary Clearance
30.472 [uH] = Ldc-Low Frequency Inductance
162.506 [uH] = Lm-Mutual Inductance
0.174 [k] = Coupling Coefficient
5.75 = Number of half cycles for energy transfer at K
18.9 [uS] = Time for total energy transfer (ideal quench time)

----------------------------------------------------
Transformer Inputs:
240 [volts] = Transformer Rated Input Voltage
15000 [volts] = Transformer Rated Output Voltage
120 [mA] = Transformer Rated Output Current
50 [Hz] = Mains Frequency
240 [volts] = Transformer Applied Voltage
0 [amps] = Transformer Ballast Current

----------------------------------------------------
Transformer Outputs:
1800 [watts] = Rated Transformer Power
125000 [ohms] = Transformer Impedence
15000 [volts] = Effective Output Voltage
7.5 [amps] = Effective Input Current
1800 [watts] = Effective Input Power
0.025 [uF] = Resonant Cap Size
0.066 [uF] = LTR Cap Size (based on 120 bps)
99 [uF] = Power Factor Cap Size
21210 [volts] = Peak Voltage Across Cap
74977 [volts] = Recommended Cap Voltage Rating (not for MMC)
8.43 [joules] = Primary Cap Energy
744.1 [amps] = Primary Instantaneous Current
155.7 [cm] = Spark Length (JF equation using Resonance Research Corp.
factors)

Hope this helps,

Tom L. (Hobart TAS).