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Re: Power Transformers
Tesla List wrote:
>
> >From DavidF4797-at-aol-dot-comSat Nov 9 21:34:48 1996
> Date: Sat, 9 Nov 1996 12:51:37 -0500
> From: DavidF4797-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Power Transformers
>
> In a message dated 96-11-09 03:01:35 EST, you write:
>
> <snip>
>
> << With a 2 kva transformer, you shouldn't need anything as
> large as an arc welder although it should work ok if you have one. We were
> talking about building a variable inductor at one time and think we decided
> on a range of 5 to 25 mh as the appropriate size - and of course the
> conductors need to be able to carry the full primary current easily. Your
> transformer at 2kva will draw about 9 amps from the 220 volt line. You
> should be able to push this to 4 kva or about 20 amps for short periods
> without hurting it at all. If you don't have access to a welder, you
> probably need to wind an inductor in the 10 to 20 mh range with variable
> taps
> to select the current range you want. >>
>
> Found your post on making your own inductor quite fascinating. Would you
> have any further specific suggestions on building a variable inductor, such
> as: if air core does it matter of it is bobbin wound or edge wound. If iron
> core is necessary, what should the shape of the core be (I seem to recall a C
> shaped iron core with an extra hunk of metal in the gap. I also seem to
> recall that the distance of the "extra hunk" in the gap to the rest of the
> core makes a difference in the shunting characteristics and that it needs to
> be adjusted "tuned" for the desired amount of current limiting). And does
> the core need to be laminated silicon steel core stock or will 1/2 in iron
> bar for the neighborhood hardware store work?
>
> Thanks in advance.
>
> -DavidF-
David and all,
In order to keep the size and cost down, the ballast inductor should use
some type of laminated iron core. Various designs have been proposed on
this list, ranging from large solenoids wrapped around PVC pipe, with an
adjustable laminated iron core (which won't saturate under heavy
loading). Also, "C" or "E" core reactors with some method of providing a
variable magnetic path/air gap could also be used. In any event, the
adjustable element should be made from laminated steel so that eddy
current heating doesn't get too far out of hand. Wire size should be
large enough to keep I^2R losses manageable - #6 or #8 AWG will be good
up to 50 Amps for intermittent duty. The solenoid could be wound from a
pair of #10 AWG wires in parallel to achieve about the same ampacity.
An AC welder is a handy method, since most AC welders offer ways to
easily adjust the amount of ballast inductance, some of them "on the
fly". Other alternatives include ballast inductors for high-power arc
mercury or sodium vapor lighting, or even some types of microwave
transformers with the secondaries shorted. Large arc-lighting ballast
inductors can often be found at scrapyards for $10-20 (since they have a
fair amount of copper and iron). I just purchased one at the local yard
that handles 6.5 KVA and weighs 52 pounds for about $20.
Note that high-power shunting resistors are essential to keep voltage
transients down to a manageble level when the gap is quenched. These can
be space-heaters, hot-water heater elements, or oven elements, but must
be capable of safely dissipating up to several kilowatts of heat. Not
using these can mean that inductive kickbacks will get back into your
power mains and wipe out your computer, VCR, answering machine, etc...
Safe coilin' to ya!
-- Bert --
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From: Tesla List <tesla-at-poodle.pupman-dot-com>
To: Tesla-list-subscribers-at-poodle.pupman-dot-com
Subject: Re: Capacitor charge, were is it?
Reply-To: tesla-at-pupman-dot-com
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Comment: Now running Red Hat 3.0.3 Picasso
>From lod-at-pacbell-dot-netSat Nov 9 21:35:17 1996
Date: Thu, 09 Nov 1995 17:04:20 +0000
From: GE Leyh <lod-at-pacbell-dot-net>
To: tesla-at-pupman-dot-com
Subject: Re: Capacitor charge, were is it?
Richard Hull wrote:
<snip>
> A charge about an isotropic capacity (single object) in a vacuum does
> indeed exist! The opposite charge need not reside in the immediate
> vicinity! The opposite charge is confined to the rest of space. Work
> was done on the vaccum to separate the charge at some time in the past or
> it would not be there. The work was done, usually elecrodynamically, but
> could be done mechanically. It involved two bodys of matter at one time
> or another and a source of energy. In a metallic circuit, needed to
> determine charge quantity or polarity, we have our nice little material
> electrons to commute the charge about (even though they never really
> move) and make it do work so our eyes can see what is there.
> CAHRGE EFFECT is trundeled about through conductors by the good office of
> electrons which do little real movement! Electrons can't just be rammed
> into a metal lattice by the hundreds of trillions! Charge effect can be
> transferred very rapidly though through the material. The material
> particles in matter likewise allow the charge via coulombic forces to
> react against matter also.
>
> Charge itself might well be free of matter and not inate to it. It is
> definable to us only with direct interaction with matter which are a
> bunch of atomic and molecularly locked charges in a lump. Charge implies
> potential energy only in the presence of matter! I am not rewriting the
> book on electrostatics, just wondering if the whole business isn't a
> matter of perception. I, unlike many, don't need to profer a theory to
> wonder about the way things work based on my own observations and
> thoughts about the possible interactions.
>
> Finally, if something is massless, acceleration itself has no meaning and
> is an absurdity, and thus no force and no energy could result from its
> motion at supposed super-luminal speeds. The moment matter interacts
> with anything, light velocity and our material perception is the limiting
> factor.
>
> Richard Hull, TCBOR
Well, the only thing that's safe to say at this point is that our definitions
of 'charge' are very different. Your definition of charge seems to map more
accurately onto my definition of electric field. Semantics? Perhaps.
For what it's worth, here's my definition of charge --
A fundamental property of electrons and positrons, by virtue of which:
1. Electrons repel electrons at a distance.
2. Positrons repel positrons at a distance.
3. Electrons and positrons attract each other at a distance.
Charges are always point sources, and electric lines of force terminate _only_
in electric charges.
This definition is still quite valid, as countless experiments have verified
that electric field lines _always_ terminate in either a positron or an electron,
without exception. Alternative theories are possible, but you'll have to
"do the experiment" that proves them in order to become famous.
-GL
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