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RE: oops ("Kickback" and untuned coils)

>> Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
>>
>> Hi Ed:
>>
>> I'd like to come to a better understanding of the hazards of coiling to
>> appliances, and in particular, just what are these ill-defined demons.
>>
>> I don't understand your suggestion that an untuned coil is more prone to
>> sending HV transients over the AC line.  My current thinking has it where
an
>> untuned coil is simply not efficient at transferring the primary energy
to
>> the secondary, so the energy languishes in the primary tank circuit for a
>> longer than desired time, burning up energy in the gap and putting more
>> cycles and wear and tear on the tank capacitor.  But I don't see any
>> mechanism for this energy to get back to the AC mains any more-so than in
a
>> tuned coil.  While the duration of each "bang" ringdown is longer, the
>> magnitude of any coupled transients would be no greater.
>>
>> Regards, Gary Lau
>> Waltham, MA USA
>>

>Original Poster: "Edward Wingate" <ewing7-at-rochester.rr-dot-com> 

>Gary,

>An untuned coil will produce transient voltage spikes/peaks in the primary
tank
>that are much higher in amplitude than a properly tuned coil and the
>untransfered energy does not just "languish" in the tank circuit, it finds
it's
>way back to the "mains" through the gap and transformer. Granted, a
properly
>tuned coil will produce a certain amount of kickback too, hence the need
>for EMI
>filters on the line feed, but not to the extent that an untuned or badly
tuned
>coil does.
>
>Harry Goldman, editor of the TCBA Newsletter once printed a letter from a
>newbie
>who wanted to know why there were SPARKS ARCING across the slots in the
WALL
>OUTLETS in his home when he fired his newly constructed Tesla coil! How
long do
>you think a microwave or any other solid state device with microprocessor
>controlled displays or functions would last if plugged into those outlets?!
If
>there were sparks across the outlets, what could be happening inside the
>walls!!
>
>Ed Wingate RATCB
>Brockport, NY USA

I didn't mean to suggest that voltage spikes don't occur or that they are
unlikely to damage appliances with semiconductor circuitry.  The maximum
amplitude of the voltage in the primary tank circuit cannot exceed the
(static) gap breakdown voltage, regardless of tuning.  This ignores the
zero-gap-current-crossing transients, but these are also unaffected by
tuning.  I simply don't see the mechanism to support the suggestion that the
mains spikes are larger or more troublesome when a coil is out of tune.  If
anyone can explain this mechanism, that would go a long way towards finding
a cure.  If not, I remain unconvinced that tuning is a factor.

Gary Lau
Waltham, MA USA