[Prev][Next][Index][Thread]
Re: TC Electrostatics (fwd)
Tesla List wrote:
> Subscriber: rwstephens-at-headwaters-dot-com Mon Jan 6 22:24:46 1997
> Date: Mon, 6 Jan 1997 20:08:19 -0500
> From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: TC Electrostatics (fwd)
>
<SNIP>
> > > Bert Hickman wrote:
> > > [snip]
> > > > > > Increasing Cp, Vg, and X, or decreasing Cs will increase Vs. However, Vs
> > > > > > increases linearly with increasing Vg, but only as the square-root of
> > > > > > the ratio of Cp/Cs. Large systems tend to significantly increase both Vg
> > > > > > and Cp, while only moderately increasing Cs (to protect the secondary
> > > > > > and prevent breakout at higher voltages). Not obvious from the simple
> > > > > > equations above is that while increasing Cs may reduce output voltage,
> > > > > > it may increase overall coil performance and sparklength for a variety
> > > > > > of other reasons! Trying to maximize output voltage is not the whole
> > > > > > story.
> > > [snip]
> > > > > > -- Bert --
> > >
> > > Hi Bert,
> > > Great analysis -- Starting with the conservation of energy is a good way
> > > to arrive at a practical conclusion.
> > > I am curious to know your opinions on what other parameters besides Vout
> > > are important to overall coil performance.
> > >
> > > -GL
> >
> > Greg,
> >
> > Thanks! I'll assume good pulse-rated caps and good, high-Q, construction
> > techniques are a given. After looking at Robert Stephen's video, and
> > reviewing the data from Chuck Curren on the Cox'es coil, I'm beginning
> > to think that rotary quenching performance may not be nearly as critical
> > as I once thought. Bang size and rep rate have got to be key parameters.
> > In the final analysis, brute force power can overcome _lots_ of other
> > system inefficiencies! :^)
>
> RWS- Bert, I just have to step in here. I appreciate that what you just
> said about brute power was said somewhat tounge-in-cheek, but there
> is also truth to that statement in many cases, hence the expression,
> "Don't use more force, just get a bigger hammer!" There are many
> technical areas in coiling where throwing more power at the system
> will not increase streamer length output, but very definitely will
> increase smoke output! Quenching performance, one of these technical
> areas, is critical to the successful operation of any coil. As you
> increase power levels, as you are well aware, quenching becomes more difficult
> to accomplish. Quenching is certainly one stumbleblock where
> throwing more power at the problem will absolutely not increase
> output, and rather the opposite occurs in practice. You may not be aware
> that my rotary system in MTC is now on its third differently configured rotating
> wheel, and the stationary contacts are now about 4th generation. All parameters
> including break rate, contact dwell, electrode material and air flow
> have undergone laborious fine tuning. It now quenches
> so superbly that I do not require the crutch solution of additional
> series quench gaps and their associated introduced gap losses.
>
> I consider the actual efficiency of my MTC system to be right up there with the
> best. This two coil classical system achieves or exceeds the same streamer
> lengths at 7 kVa that Hull's group is achieving with their highly engineered,
> sophisticated magnifiers! At just 2.5 kVa my MTC produces 6-7 foot measured
> streamers if I downsize the topload to allow breakout at this more commonly
> experienced coiler power level, and reduce my system cap to just 0.05 mfd
> instead of 0.12 mfd. No bigger hammer anywhere here at all, just highly
> efficient, synergistic design. Its a case of making a lumped parameter system
> outa just the right type of lumps. : )
Yeah, it was tongue-in cheek! For maximum efficiency, a better quenching
gap is essential - no argument here whatsoever. However, if I look at
Cox's Museum coil, with the beefy gap electrodes and low rotational
speed, it's also clear that having a sophisticated and optimized gap is
not an _essential_ prerequisite to excellent spark production. It could
be that his larger electrodes simply conduct arc heat away so rapidly
that little metal plasma is actually formed - giving him longer gap life
and merely adequate quenching. I really am looking forward to seeing
this system!
>
> > Another big factor would have to be sizing the ROC of the top terminal
> > and E-field control so that it does not break out prematurely, and that
> > streamers don't preferentially strike downward to the primary. Certainly
> > the length of the secondary is also a significant factor - it must be
> > long enough to provide adequate physical seperation between the toroid
> > and the primary as well as to itself on a 2-coil system. Larger
> > diameter, squatter coils might otherwise be better performers with their
> > higher L versus C ratio. Electromagnetic coupling between
> > primary:secondary should be as tight as insulation will withstand - and
> > probably close to a "magic" value to reduce energy-stranding in the
> > primary circuit. I'd really like to see if 0.28 could be achieved on a
> > 2-coil system! A low-impedance path between the coil base and the other
> > "plate" of the secondary's capacitance is a significant factor, more-so
> > with lower Zo coils.
>
> > Coil Zo itself is a poser! Obviously using too fine a wire gauge can
> > hurt performance, but a lot has to do with whether its direct driven
> > (no-one will dispute RH's results using a 30 Gauge resonator!), and the
> > degree to which the coil is behaving as a distributed transmission line
> > or a lumped LC. Results on your big coil, and Cox's Milwaukee Museum
> > coil seem to indicate that heavy topload C is not an automatic
> > prerequisite for great performance!!
>
> RWS- Bert, see my post today on topload size.
Saw it.. voltage withstand of the secondary is certainly another
limiting factor in determining how short the secondary can be on a
2-coil system. You've been able to successfully use E-field control to
direct streamers away from the primary... but it now looks like you "hit
the wall" for the particular insulation system used on your
secondary... Looks like re-wind time!
>
> BTW, do you have any conclusions
> > from the Zo/coil performance information you were gathering last year?
> >
> > Still lots of mysteries in coiling, Greg!
> >
> > Safe coiling to you!
> >
> > -- Bert --
>
> Lots of mysteries and generalizations for sure, but we seem to be
> narrowing and fine tuning this all down thanks to the excellent work
> of a growing number of knowledgeable coilers such as yourself sharing their
> ideas and experiences on this forum, and the tremendous benefit that the
> existence of this forum provides thanks to a very tirelessly dedicated Chip
> Atkinson. Keep up the good work, all!
>
> rwstephens
Second the sentiment - Way to go Chip!!
-- Bert --