Re: Weird ideas
From: David Sharpe[SMTP:sccr4us-at-erols-dot-com]
Reply To: sccr4us-at-erols-dot-com
Sent: Sunday, December 07, 1997 9:03 PM
To: Tesla List
Subject: Re: Weird ideas
Tesla List wrote:
> From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
> Sent: Saturday, December 06, 1997 6:02 PM
> To: Tesla List
> Subject: Re: Weird ideas
> At 03:16 AM 12/5/97 +0000, you wrote:
> >From: Edward V. Phillips[SMTP:ed-at-alumni.caltech.edu]
> >Sent: Thursday, December 04, 1997 11:39 AM
> >To: tesla-at-pupman-dot-com
> >Subject: RE: Weird ideas
> >" Ed -
> > What are the wallplug efficiencies including filament losses and connected
> >as Tesla coils. How would these systems compare with Tesla coils with the
> >same wallplug input ?
> > John Couture"
> > Not quite sure I understand your question. If you mean the
> >efficiency of one of those transmitters (operating at the correct
> >frequency, of course) driving the primary of a TC, I would think
> >the efficiency would be as high or higher, since there is no
> >requirement for amplitude modulation and its attendant input power.
> >I suspect the conversion efficiency of a spark-excited TC is quite
> >a bit less, based on the heating of the primary gap. I don't
> >believe efficiency in "transformation" of primary input to secondary
> >output (into the streamers) means much, because of the heavy
> >loading of the secondary by the streamers. That means, by the
> >way, that I think the emphasis on secondary Q is probably misplaced.....
> Ed -
> With the present method of rating a Tesla coil I admit that it is
> difficult to understand what a person means by Tesla coil efficiency.
> Efficiency is a ratio of energy out divided by energy in. With sparks the
> energy out is difficult or impossible to determine.
> What I meant was when using a certain wallplug input to a tube type TC
> would you get a longer or shorter controlled spark length compared to a
> classical TC using the same wallplug input ? A controlled spark length being
> a horizontal continuous spark from the secondary terminal to a ground point,
> using standard air corrections if necessary. This type of rating leaves a
> lot to be desired but is the simplest and makes good sense from a scientific
> standpoint compared to the rare extra long spark normally used.
> John Couture
John, Ed, All
Based on what experiences I have with VTTC's and what I've observed,
since a VTTC is based on a class C oscillator, and is CW (continuous
wave) more or less, the AC to RF conversion process HAS HIGHER
efficiency (Energy in = energy out + losses).
However, a VTTC will NEVER produce spark lengths per unit input power
that a capacitive discharge coil can. My current push pull hartley
oscillator is running with approx. 2kW input power and with level
shifting approaches 25kW pk power (6.3kV pk X 2A X 2 [push-pull]), yet
the maximum spark length my system will produce is 18-19". Within 6', I
have 1 kW magnifer (9kVAC, 0.0108uF, Tesla equidrive, 6 point biphase
gap) which will routinely produce 36" and on occasion 42" discharges.
The key is dumping 1/2CV^2 in microseconds at interrupt rates of 240
to 480 IPS real. The peak power will be as much as 2 orders of
magnitude greater for a capacitive discharge system then a VTTC of
equivalent input powers. I am observing efficiencies in the 75 to 80%
range (RF tank to AC input power). What's actually coming out of the
sparks and streamers is anyone's guess, but I can MELT AND GLOBULIZE
28 gauge wire at 1" per second at full power!!!
DAVE SHARPE, TCBOR