LTR Coil Power Calculations

Hi All,

I have been running my new coil through MicroSim to see what kind of power
throughput my new coil will have.  Here are some of the details...

The primary cap (27.9nF) is charged by a 15kV/60mA neon transformer.  The
firing voltage is 21kV with the gap (sync) being set to fire 1.324mS (29
degrees) after the voltage peak (LTR coils like late firing).  That is 6.17
Joules per bang.

The power distribution in the system is as follows:

Neon Primary = 30.6 watts
Neon Secondary = 38.87 watts
Filter Resistors = 98.4 watts
Spark Gap = 386.5 watts
Secondary Losses = 54.4 watts
Power to Arc = 283.5 watts
Total Power = 892.3 watts

I then calculated the power to the arc with different coupling:

K = 0.201	301 watts
K = 0.171	290.4 watts
K = 0.145	285.1 watts
K = 0.123	281.1 watts
K = 0.108	268.4 watts
K = 0.089	227.6 watts

This is interesting since it suggests that the coupling is not very
critical.  I may be able to back off the coupling to get a better quench
without too much real loss of power.  I suspect the lower couplings have
longer transfer times that allow more time for the primary circuit to burn
up power.

I then calculated the power output using two coils (large and small) and
two torroids (large and small).

Large Coil with Large Torroid
Lp = 121.7 uH
Ls = 75.4 mH
Cself = 15.7 pF
Ctop = 29.0 pF
Power to Arc = 286.9 watts

Large Coil with Small Torroid
Lp = 71.6 uH
Ls = 75.4 mH
Cself = 15.7 pF
Ctop = 11.0 pF
Power to Arc = 278.4 watts

Small Coil with Large Torroid
Lp = 34.12 uH
Ls = 22.1 mH
Cself = 10.0 pF
Ctop = 35 pF
Power to Arc = 183.75 watts

Small Coil with Small Torroid
Lp = 18.55 uH
Ls = 22.1 mH
Cself = 10.0 pF
Ctop = 14.5 pF
Power to Arc = 184.1 watts

This is really interesting because the torroid size does not seem to matter
but the coil size does.  I suspect the larger coil gives lower primary
current which reduces the primary system losses.  The small torroid seemed
to give slightly better arc power.  Much to ponder and much to test...

The MicroSim 8.0 model of this is at:




BTW - Chip and I know the www.pupman-dot-com site is down.  I have not heard
back as to what the matter is yet...