Re: Resonant capacitor charging calculations QUESTION - answered?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Pete Komen by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<pkomen-at-zianet-dot-com>

> That leaves the question of what happens to the current in the primary of an
> ignition coil while a cap is discharging through it and the secondary arcs.
> I expect it to jump to a high value, but how high?  If I build this circuit,
> I could try it at low voltage and watch what happens on a scope.  All I need
> is time.

Look at the waveforms here:
http://home.datacomm.ch/k.schraner/induction_coils.htm
When the current is interrupted at the primary of an induction coil,
the sequence of events is:
1) The primary voltage starts to rise, as the current from the primary
inductor starts to charge the primary capacitor
2) The secondary voltage starts to rise too, with the capacitance at
the secondary being charged. The system operates much as a Tesla coil
before breakout during this process, oscilating at two different 
frequencies. The frequencies are very different, because the coupling
coefficient is high.
3) At some point of the first secondary voltage semicycle the secondary 
arcs. The secondary capacitance is practically short-circuited, and 
the secondary acts as a short-circuited inductance coupled to the 
primary (actually, the spark acts as a low- voltage source, 
accelerating the decay of the secondary current and inducing a DC 
component in the primary oscillations). At the exact start of the spark, 
the primary voltage shows a sudden jump in the direction of zero, 
corresponding approximately to the breakout voltage divided by the 
turns ratio of the transformer. The primary circuit sees now a low 
inductance, and if there is some energy left on it, a high-frequency 
oscillation takes place, decaying in a few ms. 
4) The secondary spark starts as a high current pulse from the discharge
of the secondary capacitance (even if just wiring. The secondary
self-capacitance doesn't discharge immediately) followed by a burst of
radiofequency oscillations, and continues as a long (several ms)
decaying 
DC current with high frequency oscillations (as in the primary) added.
5) At some instant, the secondary spark is interrupted, and the
secondary
acts again as a large inductor loaded with a small capacitance. If there
is still energy in the system, some cycles of double oscillation, as
in the starting phase, appear again, until all the energy is dissipated.

As you see, the process is quite complicated. A spark from a Tesla
coil to a grounded object also follows a similar sequence. The main
difference is that the secondary voltage takes some cycles to
rise enough for breakout, and the double oscillations take the
shape of beats, because the two frequencies are not very different,
due to the low coupling.

Antonio Carlos M. de Queiroz