Re: Notes on Terry's observations
>If the coil is designed to operate with already some loss due
>to skin effect and other losses that increase with frequency at
>the resonance frequency with a large top load, the other resonances
>will be at much higher frequency, and so will be heavily damped,
>as you correctly point out.
>About "racing sparks", I still believe that the reason is simply
>the accumulation of static charges in the surface of the resonator.
>Antonio Carlos M. de Queiroz
The graph at:
Shows the current draw of the coil generally increasing as frequency is
increased. I think this is due to the increasing losses in the coil.
It is interesting to note that at about 110.01kHz the current drops to
almost zero (660nA) (I notice that I now us the term "about" for 5 digit
numbers ;-). The graph takes data at every 10kHz so it missed the true
level of the peak before at 84.63kHz. It was 1.07mA About a 1:1600 ratio.
The input voltage is 0.707 Vrms. The resistance at the peak is 660 ohms
while the low current point had a resistance of 1.07M ohm. The wire on the
coil is 2690 feet long. That gives a 1/4 wave frequency of 91410 Hz. I
could not find any correlation between the frequency and anything I
measured but I don't think that is a surprise. However, I did try...
IMHO, I think racing arcs are caused by pure transformer action as the
secondary coil is suddenly hit by the first impulse from the primary. A 15
turn primary mixed with the lower say 300 turns of the secondary gives a
voltage transformation ratio of 20. So the 20kV on the primary gets
transformed to 400kV before the resonant action can start. Raising the
secondary lowers the coupling and reduces the initial induced voltages so
the arcs can be stopped by moving the coils away from each other. I have
not spent a great deal of time thinking about that, so perhaps I am wrong