[RFI] Whirlpool Duet Washing Machine RFI update

[Jim Brown]

On Fri, 11 Feb 2005 12:38:41 -0800, Kelly Johnson wrote:

>If the washer
>meets Part 15 emission standards, yet it still causes interference
>then the owner of the washer is responsible for complying with Part 15
>"usage" regulations. 

Yes, but I'm guessing that it may not conform to Part 15 emissions for Class 
B. FWIW, variable frequency drives are known to be problematic with audio 
systems, and it may be due to magnetic fields established by improper 
grounding, or by filters that bypass enough current to "ground" to establish 
such a field. 

On a pro audio list I frequent, a sound contractor is currently wrestling 
with EMI from a newly installed geothermal heating system that uses a 
variable frequency drive (VFD). The unit was ordered and installed without 
the optional filter kit, and the VFD is getting into EVERYTHING associated 
with an existing audio system. 

There may also be an extra (and improper) bond between neutral and ground at 
the motor (either the washer or the geothermal heater). Such an extra bond 
would establish such a magnetic field, which would then couple into any 
current loop within its loop area. And this field could be established by a 
capacitor between neutral and ground or the phase (hot) and ground that had 
low enough impedance at the frequency of the motor drive/noise. 

Jim Brown  K9YC