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Re: the cure for racing sparks
Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <DR.RESONANCE-at-next-wave-dot-net>
Any time you exceed "critical coupling" you begin the freq. splitting of the
main F (resonant) freq. As soon as you have two separate frequencies you
get oscillatory beats.
I fly a twin engine Piper Aztec and the same exact effect occurs. If you
get one prop running just 10-25 rpms above the other there is a noticeable
beating effect which is corrected with the prop governor controls (prop
pitch). The "beats" will drive the pilot nuts in a few minutes if not
The same principle applies to Tesla circuits. Exceed critical coupling and
you have a HV peak at some other point than the top of the coil and "racing
sparks" can occur.
Coupling adjust, as you mentioned, is the cure.
Many beginners have set up coils without enough primary inductance available
to tune properly and this also produces the same effect.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Thursday, July 11, 2002 7:08 AM
Subject: Re: the cure for racing sparks
> Original poster: "boris petkovic by way of Terry Fritz
> > Two things come to mind. First, racing sparks are
> > usually caused by either
> > too small a toroid on top which provides ineffective
> > electostatic field
> > control down the coil and second, the usual culprit,
> > not enough available
> > inductance in the primary (too few turns) to hit the
> > proper tuning point.
> > You are tuning at the wrong primary resonance point.
> Yes,this explanation relating toroid size-field
> control-detuning combining effects holds.
> > A second note is that you may be "overcoupled" which
> > causes the
> > "double-hump" on the freq, ie, splitting the res.
> > freq. into two different
> > freqs which beat against each other.
> Overcoupling (ie.increased coupling) introduces a more
> frequency split -more expressed "double hump" in a
> freq. spectrum of coil as you say,but that spliting
> -beating frequencies against each other whatever,isn't
> direct cause of racing sparks .It is overcoupling
> itself.More coupling means less space between primary
> and secondary + faster transfer of energy from primary
> to secondary with less energy loss when compared with
> smaller coupling.That results in stronger local fields
> and higher secondary voltage for given input
> energy.Therefore ,it again comes to field control as
> stated above.