[RFI] Washer RFI/EMI
w9ac at arrl.net
Mon Sep 7 05:21:14 PDT 2009
> In other words, you do NOT want the chassis or "ground" to be part of the
> current path, either at the fundamental frequency or at the high harmonics
> (RF) that are causing us grief.
My thought is to isolate any existing cabinet shielding from the RFI
abatement. This would include using large #31 toroids on the VFD cabling
close to the motor connect point, and also close to the serving VFD circuit
point that connects the motor by wires. But as you know Jim, trying to get
ample turns to provide enough choking reactance oftentimes means extending
the wires. -- and that can turn into a real project. When I attack this,
I'll try to document the inside changes if I'm successful. The toroids are
here -- it's just a matter of doing this when the XYL is away <g>.
I've also given consideration to the filing of a Petition for Rulemaking
with the FCC to amend Part 15 to include "appliances" that are currently
exempt from meeting RFI standards. But that kind of filing needs the
backing of interested organizations. The EU nations have been more
proactive on this front and my understanding is that their household
appliances must meet the same strict RFI/EMI standards as is required of
other electronic equipment.
This is an area ripe for organizations like the ARRL, NAB, SBE, AES, and the
like to join forces. It's interesting to note that in the most recent
edition of RadioWorld, a well-read broadcast engineering publication, the
front page story addressed the gradual increase in average noise floor over
time from unintentional radiators. The point the author was making, is that
the rise in noise floor due to these devices is already having a devastating
impact on analog AM and HD radio services in North America. What the author
did not address is the fact that the rise in noise floor is due in large
part to exempt appliances that internally use computers, inverters, and
switch-mode power supplies in everything from the clothes washer to the
toaster. These internal devises by themselves must meet technical
standards, but as soon as that device is thrown into an "appliance," it is
then exempt from meeting unintentional radiator standards. Why?
We really need to get Part 15 current with the times. As more consumers
replace their household appliances with models that incorporate RFI/EMI
emitting technology, the problem will only become worse.
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