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shadow 11th May 2002 07:43 PM

Transformer shielding
There is some words said about this theme,but nothing to start building from.
I'm looking for cheaper method to shield toroid,like steel(good for shielding)and copper(shielding unknown for me)
So what do you think about steel and copper composite.steel(1.5mm)and copper 0.7mm or more.I have something on my mind and i keep you informed.All very experimental,but who knows.

Any theoretical stuff,or DIY projects are very welcome.

peranders 11th May 2002 09:58 PM

Magnetic sheild
May I ask WHY you want to sheild a toroid tranformer? Toroids are known to have very little magnetic field, one a the big advantages! But the guy swedish Mats Bladelius (Advantage, S.A.T don't have the URL's) have toroids with a magnetic shield, see article at ELFA.

Text only in swedish, sorry..

Jocko Homo 11th May 2002 10:58 PM

Your toroid would benefit more from an electrostaic shield between the windings.

And no DC on the AC mains.


shadow 12th May 2002 09:26 AM

I know all about low magnetic field,but some people still practise shielding.
I am one of those who dont ask how much improvement,but DIY pleasure is always there :)

Dont know if is realy worth ...

peranders 12th May 2002 09:45 AM

shadow, if you still want to shield the toroid you should have soft iron as material but I think regular iron will do. See the picture of the audio transformer above. This transformer has a ring of soft iron around the toroid ring.

Petter 12th May 2002 10:05 AM

Magnetic shielding for toroids is typically some core material wrapped around the circumference of the toroid. This is very effective.

As for CU shielding, you really only need extremely thin layers of conductive material to effectively set up a shield. However, if you have several such layers with a distance between them, you are much better off. You often see plastic cases where conductive paint has been applied internally and externally for this very purpose.

I would recommend that you use the core material method above and set up your toroid so that you can turn it for minimum effect on circuitry.

If you are still worried, set up the transformer in a dedicated box some distance away, and use TI Shield or equivalent hi-tech material for shielding at the consumer. You can get TI Shield from Michael Percy.


jackinnj 12th May 2002 04:46 PM

Cu shielding
I have a piece of instrumentation which uses copper film laminated between two sheets of mylar for shielding. The copper film has a lead which is attached to the central ground point. If you can find the copper film, you could easily laminate it between two sheets of clear avery adhesive film. (btw, I have found the avery clear sheets to be excellent for making PCB masks, although a little expensive.)

shadow 12th May 2002 07:41 PM

So how thick is this copper film?
I know work on 0.7mm plate.I use double layer with no mylar.
But why use mylar?

Petter 12th May 2002 08:42 PM

Why use mylar?

Because you need to have isolation between them, otherwise it is just a thicker piece of metal. You can and should connect them, but use only 1 connection point for entire "wrap".


peranders 12th May 2002 09:56 PM

Re: Cu shielding

Originally posted by jackinnj
(btw, I have found the avery clear sheets to be excellent for making PCB masks, although a little expensive.)
Belive it or not ordinary tape works fine! Transparent, brown, anything in plastic!

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