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Re: Gap Losses
Tesla List wrote:
>
> > Subject: Re: Top Toroid
>
> Subject: Gap Losses
>
> >
> > Skip -
> >
> > What might be happening is that early firing on the 60Hz waveform
> > leaves magnetic energy stored in the transformer's core. Hence, you
> > are not only dumping the capacitor's energy, you are also dumping
> > the residual energy in the transformer as well. If the gap fires
> > late, then cap voltage goes down, but the transformer is now 'cooling
> > off' with less energy available.
> >
> > - Brent (bturner-at-apc-dot-net)
>
> Hey, let me get in here and stick my foot in my mouth!
> Could it be that when there is early firing you have *more* sets of gap
> sparks for the duration of time that the electrodes of the rotary gap are
> lined up?
I don't think so. The charging current capacity of the neon is
proportional to the voltage so after the initial bang the neon doesn't
contribute much. Any further arcing is caused by the kickbacks from the
secondary.
To put it another way: if the gap fires more often, won't it
> naturally get hotter?
I think it will get hotter but only because the current in each new arc
is lower and I believe that the resistance of the gap goes UP at lower
currents.
>
> When you synchronize the rotary gap to fire at the peak of the capacitor's
> voltage charge won't there be fewer sparks during the time the gaps are
> lined up?
It appears that when you have set up for maximum discharge length, the
gap actually prefires before the gap contacts have gotten across from
each other. Setting the phase to fire later, when the gap contacts are
more nearly across from each other, dramatically reduces discharge
length.
The initial spark across the gap will conduct more energy, but
> more energy *conducting* does not necesarily mean more heating of the gap.
>
> The temperature of the gap is a function of heat _losses_, and when the
> capacitor initially discharges at its peak, I think we will all be
> surprised to find that this is *not* where the gap wastes the most energy.
> In fact, my gut feeling is that this is actually where the gap functions
> most efficiently.
I totally agree with this. Higher current, therefore higher power, shows
up as cooler contacts and longer discharges.
>
> I would not be at all surprised if testing were to show that when the
> breakdown voltage of a gap goes above a certain value, its actual
> resistance per firing is *lower*. Sort of like when certain materials
> become super-luminant and increase in efficiency when pushed past a certain
> limit.
>
> Tesla's researches into luminant gases were, in my opinion, more than just
> a side issue. He was studying plasmas. Why? Aren't spark gaps deeply
> involved with plasmas? He mentioned several times that an excited gas could
> carry currents much more efficiently than the best copper conductor. I
> don't think he was just referring to his light experiments, but also to
> what he had learned about spark gaps.
>
> This could explain some of the advantages that rotary spark gaps exhibit,
> and maybe lead someone to explore if energy efficiency would increase if a
> rotary spark gap were to have electrodes that were large in conduction
> area, but small in width. This type of electrode, set up to fire *once* at
> each peak charging point of a capacitor might produce some very interesting
> pulses! I believe the electrodes for such a rotary spark gap would probably
> be pulled much further away from one another than is currently the custom.
>
> By the way, did you ever wonder why Tesla was interested in operating some
> of his Tesla coils from special AC generators that he designed that allowed
> him to use primary frequencies that were way above 60Hz? Could it be that
> at a frequency of say 400 Hz one might be able to increase the firing rate
> and still be operating the rotary gap in a synchronized fashion such that
> each firing would be at a large peak value?
Not only did Tesla do this but I believe that some on the list have
experimented with mains frequencies above 60 hz. Higher mains
frequencies translate into more bangs per unit time and therefore more
energy processed into the secondary.
Skip
>
> OK, now that I have firmly placed my foot in my mouth, let's see what the
> experts say... This should be fun!
>
> I believe someone out there at one time or another used fiber optic cable
> to help see what was going on when the rotary gap fired. Does this
> individual remember if there was a correlation between the firing angle and
> the number of times the gap fired during the time the electrodes were lined
> up?
>
> Conjecture is fine, but data always brings out the truth.
>
> Fr. Tom McGahee