Re: Critical TC Size

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

Original poster: "D.Wightman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dwightman-at-mmcable-dot-com>

A very simple question, What is "CW" mode?
Thanks.
D.Wightman











> A low duty-cycle pulsed mode of operation is more efficient at
> maintaining the ion channel than a CW mode, as the ions have a
> persistence of several mS that can be exploited between pulses.
> If the duty-cycle is increased, then the peak power starts to
> approach the CW average power, and this pulsed advantage is
> eventually lost. Note that CW coils suffer far lower arc length
> to input power ratios than pulsed coils, even though their arcs
> are decidedly 'bushier'.
> 
> If a formed ion channel has a finite lifetime, then it follows
> that there will be a *minimum* firing rate that can properly
> exploit this ion persistence.
> 
> Now as the coil continues to grow in size, far past the human
> scale, it's natural resonant frequency continues to decrease.
> Consequently, the fill time required to transfer energy to the
> secondary increases.
> 
> At some point this fill time must adversely impact either the
> maximum possible break rate, or the operating duty-cycle. In
> either case the coil's performance will begin to suffer, and at
> larger coil scales a rather unfortunate knee feature appears
> in the 'arc length vs. grid power' curve.
> 
> To compensate, one can employ a variety of tricks to prop up the
> resonant freq, such as space-winding the secondary, but then at
> some point the secondary impedance will begin to drop too far,
> interfering with the coupling of the power to the arc.
> 
> Eventually at some critical scale one runs out of design options
> for maintaining the coil's arc production efficiency as the resonant
> period of the coil collides with the fixed ion lifetimes in the arc
> channel... which moves the operating mode from pulsed to CW. Increasing
> the coils' scale beyond this critical point results in considerably
> larger increases in the prime power draw to obtain longer sparks, and
> very quickly one runs out of options for connecting such a beast to
> any practical point on the US power grid. (Now France, perhaps...)
> 
> Ultimately the coil's maximum size will be defined by the finite
> persistence of the ions in the arc channel, which I shall assume not
> to be adjustable.  My first-order attempts at designing a coil to
> this critical scale result in a secondary somewhere around 110ft in
> height, and 22ft in diameter.  This is the present design target for
> the Advanced Lightning Facility.  These dimensions are likely to
> change to some degree, as more detailed information on arc creation
> and maintenance at these scales is collected, and/or if I can coerce
> the TSSP at some point to simulate such an impractical example.  ^_^
> 
> 
> -GL
> www.lod-dot-org
> 
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