View Single Post
  #6   Report Post  
Posted to sci.electronics.repair
David Platt David Platt is offline
external usenet poster
 
Posts: 75
Default Fan causing MW RFI

Jeff Layman wrote:
I have a 6-months old Fantasia ceiling fan (mains powered, with 6-speed
reversible dc motor) which is causing a lot of interference on MW. FM
is not affected. The interference is there on forward or reverse
rotation, worsens as the speed is increased,, and appears on portable as
well as mains-powered radios.

I can return it to the supplier for replacement or refund, but it is a
bit of a rigmarole to remove and refit. All the electronics are sealed
in, and the only accessible wiring is to the mains connector. Is there
any point in trying some sort of screening or RFI suppression on the
mains wiring before I take it down?


I would certainly try a noise filter at the mains connection. This
would block conducted EMI pretty effectively, which is likely the path
through which the noise is getting out of the fan unit.

Corcom (TE Connectivity) and other companies make modular filter
"cans" which might help a lot. They have various combinations of
shunt C, and series L (wired up for common-mode and differential-mode
suppression), with different amperage ratings and different sorts of
termination.

A Corcom model 3VW1 might be the sort of thing you're looking for... 3
ampere limit (up to 250 VAC), has both common-mode and differential-
mode inductive filters, "effective to control emissions in equipment
using SCR and TTL circuits for compliance with FCC Part 15, Subpart J
and EN55022, Level A, down to 150 kHz."

This "can" model has .25"/6.3mm spade-lug terminals for the line and
load side... Corcom does make some which have wire-lead terminals but
none in the W series, unfortunately.

If the fan is hard-wired to the mains (you didn't say) then installing
a module of this sort in the junction box would be the way to go. If
it's a plug-in to a mains outlet, then you'd need to build some sort
of goes-in-between box or a "filtering jumper cable".

There are quite a few other manufacturers of similar sealed EMI filter
modules... Corcom is just the best-known-to-me.

These sorts of filters are commonly available through surplus channels
(online dealers, ham-radio flea-market sales, etc.) as well as through
distributors such as Mouser and Digi-Key.