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Re: Transformer location/Safety



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



Eddy current losses ( circular in nature) induced in the aluminum by the primary circuit could also increase losses from the pri. The object is to keep as much energy as possible in the pri and then couple it into the sec without "giving it away" in the form of parasitic losses such as mounting metal components directly under the primary when they do not have to be mounted there in the first place.

I agree with your excellent accessment of skin depth and it's effects.

Dr. Resonance




Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>

Hi,

The shielding effectiveness of a infinite metal sheet to a magnetic field is
a function of the skin depth in the metal at the frequency of the magnetic
field. If the thickness of the sheet relative to skin depth is small the
shielding will not be effective. (say 10% reduction) If the thickness of the
metal sheet is large relative to the skin depth the shielding will be very
effective (say 90% reduction). From memory the skin depth in aluminum at the
usually Tesla coil frequencies is less than a 1mm so 1mm of aluminum sheet
should reduce the field to say less than 10%. Other factors such as joints
and size of the shield will have an effect as well.

Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, April 17, 2006 4:53 PM
Subject: Re: Transformer location/Safety


> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
>
>
> Bad idea.  I've already several reasons on this list why mounting the
> nst under the primary is a bad idea but people keep trying to do it
> wrong anyway.  Magnetic field sweeps upward as well as downward and
> will go right thru you aluminum shield to induce currents in your
> copper xmfr windings. Also, downward sweeping magnetic fields will
> give up power, ie losses, in anything iron, steel, etc below the
> primary.  Just don't do it --- it's very bad basic engineering!!!
>
> Aluminum does not stop a magnetic field.  In high power Tokamaks they
> wind the high current windings on the "outside" of the aluminum
> container so the magnetic fields can effect the conductive plasma
> inside the container.
>
> Mount your nst in a box 4-5 ft away from the coil and you will be
> miles ahead without losing power or inducing RF currents into your
> xmfr windings.
>
> Dr. Resonance
>
>
>
> >Original poster: "Rich" <rdjmgmt@xxxxxxxxxx>
> >
> >Spring is here and I am ready to start my next coil and was hoping to
> >put my HV transformer on the base the same as Gerry did on this fine
> >looking setup. My question to the wise ones, would it help to place an
> >alum RF shield over the top of the transformer because mine is NOT an
> >enclosed NST. It is from a laser power supply, the windings are exposed
> >and are the highest part of the transformer.
> >   I must also add that I smile each time I see the picture of Gerry
> >standing by his setup keeping safety in mind and one hand in his pocket
> >and a good ground by being barefoot. :)
> >
> >Rich , from the middle of Missouri
> >
> >
> >
> >
> >Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> >
> >Hi Kevin,
> >
> >I run my NST farm (15KV 120ma under the primary and have no
> >problems.  It is about a 1.5 ft underneath the primary.  You can look
> >at the pictures in the directories at:
> >
> >http://hot-streamer.com/temp/GerryReynolds
> >
> >and judge for yourself.  I think if you keep things at a reasonable
> >distance underneath the primary, you will be OK.  I did think about
> >the magnetic field orientation when placing the Terry filter
> >components trying to get field cancellation where possible, but dont
> >know how critical this is at that distance.
> >
> >Gerry R.
> >
> >  >Original poster: "MakingLightning" <MakingLightning@xxxxxxxxxxx>
> >  >
> > >Does it hurt to put your main power transformer and protection > > filter
> >under
> >  >the teslacoil?
> >  >
> > >Some people have said not to put metal or protection filters under > > it
> >and
> >  >they should be put aside somewhere.
> >  >This makes sense but I have seen many coils that have everything but
> >the
> > >variac under one. In practice has anyone found out if it really > > makes
> >much
> >  >of a difference?
> >  >It sure would make for a neat package to have everything except the
> >variac
> >  >under the coil.
> >  >
> >  >Kevin
> >  >
> >  >
> >
> >
>
>
>