Re: transferring electrical energy through metal wall

[EMAIL PROTECTED] ([EMAIL PROTECTED]) wrote in message news:<[EMAIL PROTECTED]>...
> 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.
> 
> The only problem was that the steel wall absorbed all of the magnetic
> field. I had to drill a hole in the wall of the physical model, so
> that to allow the passage of the magnetic field. I inserted the
> primary coil into the hole perpendicularly to the wall, and put the
> secondary coil behind the wall with its axes parallel to the wall (for
> certain reasons). Without the metal wall, the configuration of the
> primary/secondary coil worked fine. But the introduction of the wall
> into the system brought the voltage in the secondary coil close to
> zero. It got me thinking -- I decided that even if the magnetic field
> lines could get through the hole in the wall along the inserted coil
> core, the lines had to return to the other magnetic pole of the
> primary coil. And this was where the metal wall was the barrier to the
> lines ! I thought that I would have to enlarge the hole and introduce
> an air (magnetically easily penetratable) gap between the primary coil
> and surrounding metal.
> 
> The question is, how large the hole has to be, so that to allow the
> return passage of the magnetic field lines into the opposite pole of
> the primary coil ? I thought I could use a simulation package to
> analyse the distribution of magnetic lines, and thus I could find out
> the effect of the size of the wall's hole on the efficacy of
> transmission of magnetic energy through that hole. Can you recommend
> me the simulation package which has a short and not-so-steep learning
> curve ?
> 
> Your advice would be appreciated.
> 
> Regards,
> Va1erian

> Valerian, there is an approach which doesn't require you to drill a hole   >through 
> the vessel in order to transmit information into the interior of the >vessel. The 
> drawback is that it most likely requires more than 1 watt of power. The 
>approach is the following: On the transmit side form two concentric
coils. The
>first set is used to generate a large dc field in the metal so that
it becomes >magnetically saturated. This will reduce the permeability
to near free space >levels. When this occurs you will be able to use
the second set of coils to >transmit a ac field into your vessel.