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Re: Hello from a new coiler.(quenching and stuff)
From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: Tuesday, August 05, 1997 5:23 AM
To: tesla-at-pupman-dot-com
Subject: Re: Hello from a new coiler.(quenching and stuff)
> From: Sulaiman Abdullah[SMTP:sulabd-at-hotmail-dot-com]
> Subject: Hello from a new coiler.
> I intend to make two 10 nF capacitors to use in series (0.005 uF).
> What is the largest value capacitance I can use with the above
> transformer WITHOUT cooking it ?
Sulaiman,
Welcome to the world of Tesla coiling. The specs for your coil look
good to me. You can use up to a .007uF cap with that transformer,
use safety gaps and perhaps chokes and resistors to protect it.
> 3 Could someone explain spark-gap quenching to me ?
When the cap charges up to the break-down voltage of the gap, the
gap fires. The tank circuit (primary and cap) resonates at its natural
resonant frequency. Due to energy losses and transfer, the primary
resonant energy rings down (gets weaker and weaker, i.e., and damped
wave). When the energy from the firing is gone, the capacitor has to
charge up again for the next firing. But if the gap does not quench,
then the cap cannot recharge. When the gap doesn't quench at all,
this is called "power arcing", meaning that the transformer is constantly
shorting across the gap. This tends to occur mostly at higher powers
and with non-current limited transformers.
Now for the nitty gritty. If the coupling between pri and sec is loose,
then the quenching ability of the gap is not too critical, but if the
coupling is tight, then the gap must quench faster because energy is
transfered faster when the coupling is tighter. When energy transfers
from the primary to secondary, it tends to want to transfer back to the
primary if the quench does not occur, and this is a waste of energy.
the energy does tranfer back to the secondary again, but some is lost
in the gap, and else where during the process. This transfer of energy
back and forth causes the waveforms of pri and sec to look like separate
"packets" with notches between them. Looks sort of like a AM
modulation envelope modulated with a sine wave. The gap will always
quench on a notch (where the energy is low).
By using multiple series gaps, and blowing or pulling air through the
gaps, the quenching will occur faster, thereby reducing the losses
that occur from transfering energy back and forth from primary and
secondary. At tighter couplings, this transfer of evergy also causes
new frequencies to occur and build up in amplitude to the point where
"racing" sparks can occur on (and destroy) the secondary coil. But a
fast enough quench will stop the energy transfers sooner, and reduce
the likelihood of the formation of these racing sparks. Rotary gaps
may be needed to quench adequately at higher power levels.
< 4 I'd like to operate at low-frequency / high top-capacitance,
> is it necessary to operate at the quarter-wavelength frequency ?
Yes, the TC will give the best sparks at this frequency. No need to
calculate it too closely...just tune for best sparks...but make sure
you're not running on a harmonic. Ignore physical length of wire
concerns.
> Don't toroids and guard-rails form an effective shorted-turn ?
Guard rails are built with a gap in them to prevent shorted-turn
problems. Toroids do represent a shorted turn, but absorb very
little energy due to the effect noted by Malcolm Watts in a recent
posting on this list.
Good luck and be safe!
John Freau
> I will really appreciate all your responses.
> Thanks.
>>