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Re: Harmonics

An interesting idea which might be worth a try is a resonant triggered 
coil. This would involve a small third coil loosely coupled to the main 
setup. The output of this coil is set up in such a way so that when the 
resonating coil is in the correct phase that a pulse in the primary will 
serve to increase the oscillations, this small coil would be used to 
trigger a large thyratron such as the ones used in big radar 
sets.(thyratrons are faast!) This should dump a big whallop of energy 
into the primary in the correct phase every time if you set it up 
properly. Note that the charge dumping cap will need to be carefully 
calculated (bigger is not necessarily better) such that the conduction 
phase is over before the waveform in the coil reverses phase - 
thyratrons are like scr's - once they are on, they stay on until current 
drops below a certain level. Starting mechanism for this arrangement ie 
starting before coil is oscillating will req. a bit of thought. The 
hammer and bell idea seems to be a nice analog of spark driven coil idea 


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>Original Poster: RWB355-at-aol-dot-com=20
>
>Hello Cabbott, all,
>
>You wrote:
>
>SNIP
>
>.... this is akin to pushing a swing every time it rocks back.
>
>SNIP
>
>This WAS how I thought a Tesla coil worked a while ago, too. However, 
new
>discusions and thoughts have lead me to believe this is NOT how a spark 
g=
>ap
>driven Tesla coil works.  I guess you are talking about someone sitting 
o=
>n a
>swing and a second person gives the swing a push (with the equal 
amounts =
>of
>energy each time) each time it comes back to the "pusher". This will 
let =
>the
>swing rise higher and higher after each push. Analog to this, a coil 
woul=
>d
>experience a voltage rise, which would continue to climb up and up 
(volta=
>ge
>wise). What you are talking about is resonant rise. A spark driven 
Tesla =
>coil
>does not experience resonant rise. A Tesla coil should be viewed more 
lik=
>e a
>lightly coupled transformer.
>
>You store an "x" amount of energy in the primary cap. When the gap 
fires =
>this
>energy is transferred to the primary coil. The magnetic field generated 
b=
>y
>this surge induces a voltage across the secondary (inductive energy 
trans=
>fer).
>Not all of the primary energy is transfered into the secondary during 
one
>oszillation, so you want the tank circuit to be able to "swing" a few 
tim=
>es
>(more on that in a minute), before the gap stops conducting. This is 
the
>maximum amount of energy you are able to store in the secondary. Now 
you =
>can
>transfer this energy into something usefull (like making sparks).=20
>
>A toroid sitting on top (capacitor) of the coil stores the charge and 
wil=
>l
>prevent the voltage from breaking out immediately. The bigger the 
toroid,=
> the
>higher the voltage it can store, and the longer it takes for the charge 
t=
>o be
>stored because your coil cannot deliver the voltage needed for a full 
cha=
>rge
>in one cycle. This means the coil will not arc after every bang. If you 
h=
>ave
>an excessively large toroid, you will never achive an arc, because you 
ca=
>n=B4t
>charge it high enough for breakout to occur. So, for hottest and 
longest
>sparks, you will want a toroid which will promote breakout at about 
70-90=
>% of
>the highest voltage your coil can make.
>
>You want the spark gap to stop conducting exactly at the point where 
all
>energy stored in the primary has been transfered to the secondary. This 
i=
>s the
>way I understand first notch quenching. Letting the gap conduct any 
longe=
>r
>will force the secondary to return some of its stored energy back into 
th=
>e
>primary, which means losses and therefore a shorter spark.=20
>
>I think a better picture of a spark gap driven Tesla coil would be a 
hamm=
>er
>and a bell. Your hammer is the primary circuit and the bell is your 
secon=
>dary
>coil. The bigger the hammer, the "harder" the bell rings, which is one 
re=
>ason
>why I like using a big cap and high RF currents as opposed to a high 
volt=
>age
>and a small cap. This, of course, also has to do with the fact, that I 
am
>stuck with 7.5kV NSTs (at least 6 of them in parallel can deliever 
600mA)=
> at
>the time. The problem with the low voltage / high current are the 
higher
>losses involved (IxIxR), so it might be a win or lose situation in the 
en=
>d.
>
>The spark gap driven TC is not being continuesly fed with RF. Rather, a 
g=
>ap
>driven TC is a pulsed device. A CW (e.g.:tube driven) coil might be 
able =
>to
>experience a resonance rise, although I am not quite sure of this, 
either=
>.=20
>
>A tube coil and a small magnifier (I will have to investigate what make 
a
>maggy tick) are on my long list of "still to do" things. Before I do 
this=
>,
>however, I want to get my 8" coil shaped up. Considering that I am 
(durin=
>g a
>testing phase) only dumping 0.22J into it and using almost no topload 
(ma=
>ybe
>1-3pf at most) to store the charge, I think my present spark length 
(long=
> way
>to maximum, of course) of 20" is okay.
>
>Your special setup causes interference which leads to an incredible 
volta=
>ge
>difference (you are using different wavelengths) between the two 
toroids.=
> This
>is why it should give you some really awesome sparks. If I am thinking
>correctly, firing two seperate coils 180=B0 out of phase would get you 
si=
>milar
>results.
>
>Comments and flames welcome because they are only going to help me 
unders=
>tand
>Tesla=B4s coils better.
>
>Coiler greets from germany,
>Reinhard
>
>
>


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