Hi
Another magnetics question!
I have a SMPS which uses a toroidal ferrite transformer. It switches at ~100kHz, works very well, it's not my design and I can't change it.
However, it introduces noise at about 50kHz onto/into my electronics which causes a problem. After much experimentation, I found that putting an earthed screen around the transformer kills the problem quite dramatically. The screen must be earthed, and doesn't need to be magnetic.
This is something I can do. I don't have much room but I guess that wrapping copper tape around its exposed enamelled wire will cause problems for Edward Current. Is there a rule of thumb for what sort of gap to leave between the windings and a screen? How quickly does the field drop off?
(And yes, I know not to make a shorted turn.)
Cheers