Re: Awesome Quarter Shrinking Capacitors on EBAY

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

The higher voltage (for a given energy) means that the peak current will be
higher (the circuit being the same.. the resistive losses dominate, and
higher voltage = higher current).  The higher voltage also implies a smaller
capacitance, which means that the energy is being dumped more quickly. The
net effect of both is to make the di/dt higher.  Since the di/dt is what
makes the magnetic field in the work piece, higher voltage makes more field
in the work piece, with higher field due to higher current in the work coil.
There's a fairly sophisticated optimization you can do, trading off the
di/dt, the field in the coil, the rate at which the field propagates into
the work piece, etc.  (steel has a much thinner skin depth, etc.)

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, October 11, 2003 1:39 PM
Subject: Re: Awesome Quarter Shrinking Capacitors on EBAY


 > Original poster: "Paul Marshall" <klugmann-at-hotmail-dot-com>
 >
 > One thing that I have noticed, in quarter shrinking is that total
available
 > energy does not always Guarantee success. It seems that the best results I
 > have gotten have been at higher voltages 30kv and above. Even when the
 > energy is equal. For instance, I had a 40kv 32 uf maxwell total energy 25
 > kj. I never went that far most of what I shot was between 8-12 kj. The
 > quarter was under .5". Later I used
 > a 45uf 30kV cap. Even at a full 20kJ I never reached the .5" mark. Now I
 > have a 330 uf 25kV cap which will give me 103 kJ. I will try this out
soon.
 > This cap is very low inductance.
 >
 >
 >
 > Paul S. Marshall
 >
 >
 >
 >
 >
 > >From: "Tesla list" <tesla-at-pupman-dot-com>
 > >To: tesla-at-pupman-dot-com
 > >Subject: Re: Awesome Quarter Shrinking Capacitors on EBAY
 > >Date: Thu, 09 Oct 2003 15:04:20 -0600
 > >
 > >Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 > >
 > >"Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org>
 > >
 > >John, an "m" or an "M" always refers to micro.  The standard units for
 > >capacitors are Farad, microfarad, and picofarad.  Nano and especially
 > >milli
 > >are rarely, if ever, used.  I always wondered why cap manufacturers
 > >couldn't use "u" for micro - it looks close enough to Greek "mu" and is
 > >certainly much less ambiguous than "M".
 > >
 > >I think most of us have stories of EEs showing their ignorance in front
 > >of
 > >the AAS techs....  And I have no problems admitting that I've been on
 > >both
 > >ends more than once.  ;)
 > >
 > >Cheers,
 > >
 > >Mark Broker
 > >Chief Engineer, The Geek Group"
 > >
 > >         Unfortunately the SI unit nuts are taking over the world (at
 > > least that
 > >of technical magazine editors) and in that system no number is allowed
 > >to be less than 1 or over 1000!!!  As a result, nano and milli are
 > >coming into use in printed literature at least.  It's the "in" thing to
 > >do just like some rules of etiquette or placement of silverware at the
 > >dinner table; no practical value but separates those who "know" from
 > >those ignorant fools who don't!
 > >
 > >         By the way, a 38 millifarad LV tantalum capacitors sounds much
more
 > >reasonable than a 4 millifard 4 kV oil-filled capacitor!
 > >
 > >Ed
 > >
 >