LTR Charging vs. Firing Time
I ran a computer study of charging voltage vs. firing time delay of my
sync gap. LTR coils tend to perform better if the gap fires later than the
peak voltage occurs across the main gap. This allows the inductive kick
charging (IKC) to work a bit more efficiently. The results of the study
are as follows:
Delay = Delay time in milliseconds referred to the AC line voltage. About
21.6 degrees per millisecond.
Firing Voltage = The voltage at the firing time in kV.
Overshoot = The peak voltage of the waveform in kV. The gap can fire after
Delay Firing Voltage Overshoot
0.0 4.02 7.50
0.5 7.76 -
1.0 11.22 -
1.5 14.28 -
2.0 16.83 -
2.5 18.80 19.03
3.0 20.06 20.98
3.5 20.67 22.51
4.0 20.45 23.48
4.5 19.63 23.81
5.0 17.95 23.46
5.5 15.81 22.43
6.0 12.91 20.77
6.5 9.75 18.53
7.0 6.04 15.81
7.5 2.30 12.76
8.0 1.44 9.54
So the optimum firing time for my coil is 3.5mS after the AC line voltage.
This works out to 0.0035*60*360 = 75.6 degrees (I have incorrectly quoted
this in older posts as around 30 degrees). The peak voltage can reach 24kV
as I am playing with the timing of the rotary sync gap.
A static gap should fire around 2.5 mS but would not be as ideal as a sync
gap that could fire a millisecond later. Perhaps this explains the success
of using static gaps with LTR caps. However, they would only get about 70
percent as much power per given input.
I should also note that the voltage rise across the capacitor after the gap
fires does rise fairly linearly at first and the current remains fairly
constant supporting the idea that the neon is acting like a current source
during this time.
I posted a MicroSim graph of the firing voltage and neon currents before
and after the protection filter at: