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Re: Avalon (correction, in part...)

> Date:          Sun, 12 Mar 2000 19:35:00 -0700
> To:            tesla-at-pupman-dot-com
> Subject:       Re: Avalon
> From:          Tesla List <tesla-at-pupman-dot-com>

> Original Poster: "Mark Broker" <broker-at-uwplatt.edu> 
> 
> Chris, list,
> 
> <snip>

> I've noticed several things about the big TC's spark gaps (mainly the 13M
> and Electrum).  First, 13M uses a sync, and Electrum uses Async.  Second,
> the 13M uses a pressurized (~30psi of Sulfur Hexaflouride) two-break system
> with electrodes on a 24" Diameter circle.  Electrum uses a series 8 break
> system running at STP in the open air with a 28" diameter electrode circle.
> The 13M uses a 10HP 3phase motor.  Electrum uses a 15HP 3 phase motor with a
> variable frequency speed adjustment (a standard approach to vary the speed
> of an AC motor).

Please go back and (reread) "The Model 13M Story" at www.ttr-dot-com.
You will learn that i found out (the hard and expensive way,) that my
(background) in thermodynamics with gasses and solids, was *sadly*
lacking, when I tired the pressurized nitrogen (not NO3) in the
lucite chamber that contains the rotary gap.  I (evolved) to using
a dual squarrel cage high speed blower, to force cold cooling air
throught this enclsoed chamber, and exhausting out the top.  In the
last series of runs (at 125 KVa input,) I was able to sustain the
full power operation on 13M, for upt to several minutes (at which
point, the dual six-stack variacs for voltage and current control,)
would seriously over heat.  They need to be made (into) twelve-
stack units each!  But the rotary gap is very happy, and its 
performance is consistant.  I would have had to use refrigeration
and a gas filter high pressure/high volume purge system, in order
to use the pressurised nitrogen concept, with any hope of success.
That concept was too expensive and too bulky!  So, I basically
followed the "kiss" principle (keep it simple, stupid!)  And for
additional clarification, 13M uses a single phase 10 HP 3,450
rpm motor, that I modified for salient-pole synchronous 
operation at 3,600 rpm.  And, at that velocity, the extremities
of the 24" long dual rotary arms (with their dual 1/2" dia.
2% thoriated tungsten rotary electrodes,) are moving at super-
sonic speeds!  The rotary gap motor alone, draws more then 
65 amps at 240 volts input, and must be brought up to speed
by a three-stack of variacs, to limit the inrush current to the
motor.

Best regards,
Bill Wysock.
> 
> Question:  why use so many breaks?  The spark gap is supposed to be one of
> the main sources of loss in the primary system.
> 
> Ok, on to Avalon.  I don't think that mounting the tungsten electrodes
> axially on a disk (similar to Electrum) is a good idea:  if a set screw
> isn't tight enough, or loosens over time, you have a catostrophic failure.
> If memory serves correct, a 5 kg electrode would have about 750kJ of energy
> at 3600RPM on a 24" diameter disk!  I think that electrodes should be
> mounted through the disk near the periphery.  I have a little experience
> with large DC motors (1000+HP!!), and they are HUGE compared to an AC motor
> with the same torque and HP ratings.
> 
> Use fewer disks: only one or two.  Use Aluminum or titanium (MUCH stronger,
> and expensive, but won't "creep" like aluminum will) disks if a design like
> Electrum's is to be used.  Otherwise, a G-10, or something similar.
> 
> Use a high torque 3phase AC motor, with a variable frequency controller to
> adjust speed, torque, and HP.  I have a little experience with large DC
> motors, and they are HUGE compared to an AC motor with the same torque and
> HP ratings.
> 
> In my mind, use a system like Electrum's.  However, use only two G10 disks,
> each with 4 tungsten carbide electrodes mounted through the disk on a 24"
> center-to-center diameter with a total of 4 series breaks.  Design it to run
> at some unGodly high speed (~7200RPM) using a 25HP, ultra-high torque 3Phase
> motor.  Standard high-speed bearings could be used (American Roller Bearing
> or Timken).  Mounting horizontally or vertically is something to be
> investigated.
> 
> I know that's pretty fast, but a well designed, well balanced rotor system
> will be able to handle the speed.
> 
> Please comment....
> 
> Mark
> 
> 
> 
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