Re: TESLA COIL REVISED

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Trans-world" <jaro-at-surfside-dot-net> 

Gary,
you make some good points. I'm glad that you agree that the 1:50
primary/secondary ratio would be the way to go for SOLID-STATE Tesla
coils, because feeding the primary coil with the resonant frequency of
the secondary would build up the output voltage to any level, only
limited by resistance and leakage losses.

As to the classic coil that Tesla was using, I think he was correct
when he said that using a thick wire secondary could build up voltage
to any level. It seems to me that it was his experience and applied to
the BIG coils that he was using. Of course that may not apply to small
1-foot diam. coils. Why? Perhaps because small coils have smaller
inductance and with it much higher resonant frequency.

It could be that the spark-gap discharge isn't fast enough or efficient
enough to feed a secondary that resonates at MHz frequencies. Or the
thick wire secondary still produces excessive losses at these very high
frequencies. So, as I noted in a previous email, the answer for small
Tesla coils would seem to be using a thick wire secondary, PLUS a
100-200 turn tertiary coil to reduce that high frequency.

As to the brush-like discharge, that's what Tesla saw as THE difference
between his coil and other high voltage sources. So if you build a HV
coil that doesn't have such discharge, you've built a high voltage
coil, but it's not a TRUE Tesla coil.

By the way, you said that in a classic TC, resonant rise does not
occur. Is there any experimental data supporting that?

Jaro

-----Original Message-----
From: Tesla list <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, January 02, 2004 4:35 PM
Subject: RE: [jlnlabs] TESLA COIL REVISED


 >Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
 >
 >Hi Jaro:
 >
 >Concerning spark gap-based coils, it is a common misconception that
peak
 >secondary voltage is related to secondary Q.  It is not.  The peak,
 >theoretical secondary voltage is limited strictly by the ratio of
 >pri/sec inductances or capacitances.  This comes about by the
necessary
 >observance of conservation of energy:  the energy of the secondary
 >capacitance charged to the peak secondary voltage cannot exceed the
 >energy in the primary capacitor just before the gap breaks down.
While
 >pri/sec resonance is required for energy transfer, resonant rise does
 >not occur.
 >
 >Yes, losses will be somewhat higher if a secondary has higher
 >resistance, but these losses tend to be small compared with primary
and
 >spark gap losses.
 >
 >With CW vacuum tube or solid state Tesla coils, things are different.
 >The energy transfer from primary to secondary is continuous, so
resonant
 >rise takes place in the secondary.  Only with resonant rise is Q
 >significant.  Because energy is being continuously supplied, if there
 >were zero losses (i.e. infinite Q), the secondary voltage would climb
to
 >infinity.  But of course, with finite-Q inductors and corona losses,
 >peak voltage is always limited.
 >
 >I don't see why you feel that higher frequencies are better.  AC
 >resistance of conductors and inductors increases with increasing
 >frequency, so losses would be lower as the frequency goes down.
 >Concerning the "point" of achieving a brush-like discharge, why is
that?
 >The goal for most of us on this list is to make the longest spark,
 >brush-like or otherwise, and brush-like sparks are typically not long.
 >The goal of Mr. Tesla was to transmit electrical power, so any
discharge
 >at all would be a loss and hence undesirable.
 >
 >Regards, Gary Lau
 >MA, USA
 >
 >-----Original Message-----
 >From: Tesla list [mailto:tesla-at-pupman-dot-com]
 >Sent: Friday, January 02, 2004 2:50 PM
 >To: tesla-at-pupman-dot-com
 >Subject: Re: [jlnlabs] TESLA COIL REVISED
 >
 >Original poster: "Trans-world" <jaro-at-surfside-dot-net>
 >
 >You're right that higher inductance ratio will produce higher output
 >voltage, but it will also reduce resonant frequency. My proposed
 >50-turn secondary coil has at least 100 times lower resistance, and 35
 >times lower inductance than your 1000-turn coil. That results in MUCH
 >SMALLER resistance losses, and MUCH GREATER frequency and greater Q.
 >
 >The point of Tesla coil isn't the highest voltage, but providing a
 >BRUSH-LIKE discharge. Otherwise it's just a fancy lightning generator.
 >And for that special discharge you need AT LEAST SEVERAL HUNDRED
 >kiloHertz frequency. And you can't get much more than about 100 kHz
 >from your high-inductance secondary coil. If you don't believe it,
 >here's what Tesla said about it:
 >
 >http://www.pbs-dot-org/tesla/res/res_art05.html
 >
 >Also, doesn't higher Q of a coil, translate into more powerful
 >resonance, and with it, HIGHER VOLTAGE? Remember that the lower the
 >resistance losses, the higher the voltage due to resonance will be.
 >
 >And the problem with your "Output (gain) = Einput x sqr (Ls/Lp)"
 >equation is that it doesn't include the Q of the coil. It will be true
 >for two coils made with the same diameter wire, but NOT TRUE if the
 >coils are made using different wire gauges. That's because you can
 >increase wire thickness without increasing coil's inductance, and
 >thicker wire will output higher voltage because of higher Q, than your
 >equation would predict.
 >
 >Jaro
 >
 >-----Original Message-----
 >From: Tesla list <tesla-at-pupman-dot-com>
 >Date: Tuesday, December 30, 2003 7:37 PM
 >Subject: Re: [jlnlabs] TESLA COIL REVISED
 >
 >
 >  >Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >  >
 >  >
 >  >Using several hundred turns of thin wire is the best way to
construct
 >  >classic Tesla coils.  We use 1000 to 1,400 turns on most all of our
 >coils.
 >  >Tesla's coils were mostly magnifier designs and in these designs
hi-Q
 >factor
 >  >for the "driver" coil is essential while the "resonator" coil does
not
 >  >require hi-Q for maximum output.
 >  >
 >  >You need to balance the Q factor against the load impedance and
 >to
msnip..............