Potting and sheilding transformers

[pjpoes]

I am curious to know about some reasons why toirod's are often potted, and if its ok to pot a torroid that is not already. I used to work for a company that manufactured electromagnetic clutches and brakes, and remember doing it there, but that served to permanetly attack the coil into the steel rings they were inserted into.

Does it reduce vibrations in the coil? Can/does that reduce hum? I was told once it was why transformers are potted, to reduce hum? Are transformers susceptable to EMI/RFI, do they need shielding? Can it be beneficial, especially in low level signal amplifiers like preamps or sources?

[richie00boy]

It does the following:

looks nice
resistant to damage (scraping turns)
can facilitate easier mounting
protects against loose outer windings which can buzz/vibrate

It does NOT do the following:

screen emi
screen rfi
screen hum
provide heatsinking (heat dissipation is marginally worse)