Re: transferring electrical energy through metal wall

Mark Fergerson <[EMAIL PROTECTED]> wrote in message news:
> [EMAIL PROTECTED] wrote:
> > Dear everyone,
> > 
> > I am doing a project to transfer electrical energy (about 1 W, pulsed)
> > through the metal wall (5-10 mm thick) of a pressurised vessel with an
> > efficiency 10%. I have considered the options to transfer acoustically
> > or optically, but the only suitable method turned out to be the
> > magnetic one. A primary coil on one side of the wall is fed with
> > pulsing/AC current, the resulting pulsing/AC magnetic field is
> > transferred through the metal wall, and the secondary coil on the
> > other side transforms the magnetic field into electrical current.
> 
>    This makes no sense to me. If you can drill a hole to 
> permit the passage of magnetic flux, why not just run 
> insulated wires through the hole (presuming you can seal 
> adequately around the wires afterward) at much better than 
> 10% efficiency?
> 
>    BTW, what gas(es) or liquid(s) does the vessel contain at 
> what pressure?
> 
>    Also, what sort of steel is the tank made of? If it's 
> noticeablly dissipative it may be to your advantage to 
> fabricate pole pieces (of soft iron) that can be bolted to 
> the inside of the vessel so as to direct the field where you 
> want it. Does the vessel _have_ to be steel? Do you have any 
> choice in this?
> 
>    Finally, can you tell us exactly what you're trying to do 
> with that one watt? Is a magnetic field essential, or merely 
> a means to an end?

Thank you for your reply. There is some electrical device inside of
the pressure vessel, which has to be powered up. The device moves, so
wires do not work (well enough). It has to be a contactless method of
transmission of energy through metal wall. The pressure is, say,
several tens or hundreds atmospheres. The prototype vessel has no
pressure in it yet, as I am just trying out to develop the energy
transmission system. I even allowed a hole in the wall, just to see if
this makes the transmission of magnetic field any easier through it
(the hole could be covered by a non-magnetic metal later, in
principle). The first (unpressurised) prototype is made of aluminium,
but ultimately it has to be made of steel to withstand the pressure.
It has not been decided yet what kind of steel will be used; here I
heard the suggestions that stainless steel is non-magnetic (and can be
low-conductive), and therefore will provide less absorption of
magnetic field (how much less ??). I have the knowledge of physics,
but I am not a specialist in electromagnetism; I do not know
practically such details as -- e.g. what is the difference between
ordinary steel and soft iron; what are the principles determining the
shape and the position of the "soft iron" poles ? I inserted ferrite
core into the solenoid only because I heard that ferrites amplify the
magnetic field by an order of three. But maybe ferrite core has no
place in the system...

Regards,
Va1erian


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