[RFI] RFI & Washing Machines
Christopher E. Brown
cbrown at woods.net
Sun Sep 6 14:09:28 PDT 2009
On Sun, 6 Sep 2009, Dale Svetanoff wrote:
> Great job! Thanks for posting both your efforts and results - very
> useful. One question: where did you buy the Corcom filter and can you
> give us the model or part number? I was unaware that Corcom was now making
> a filter specifically for VFDs.
> 73, Dale
First note: This will void the warranty, more more important, this is a
home appliance... It may only be 120Vac, but is likely sitting in a
general use area w/ family/kids/etc. If there is any doubt that you are
fully qualified to do the work, grab an expert...
Also, these filters go at the AC *input* _NOT_ in between the motor drive
and the motor. Putting it in front of the motor can damage the controller
and/or iverheat the filter (as well as generally breaking the washer).
In my case, the controller to motor cabling is short (< 12 inches) with
an all steel case, while I could hear the washer on all HF bands it was
not nearly as bad as some of the other I sampled with partially plastic
cases and/or long motor cable runs.
I didn't see a "this is for VFD" class of filter, but some of the filter
lines are noted for use in motor drives, and digging through app notes
I used an EMC series filter, the brag sheet says
The EMC series is the most compact dual stage filter available from Tyco
Electronics. This cost effective design has a maximum current rating of 30
amps; higher than any similar catalog product. The EMC series was designed
to address the need for more differential mode attenuation in the lower
frequency range while still maintaining high common mode performance. This
type of performance is typically needed for motor drives and switch mode
power supplies with increased operating frequencies. The EMC series is
ideal for applications that require a high level of performance in a
compact, cost effective package.
I picked up 10 10EMC3 from Mouser (Mouser P/N 592-10EMC3) for about 18$
each last year.
I picked them because of the motor note and the listed LISN 50ohm atten
Line to gnd at 1,2,10,20,30mhz as 72,72,56,50,48db
Line to line at 1,2,10,20,30mhz as 54,58,47,34,36db
The 10EMC3 is a tab mount with leads.
I also used a pair of 30EMC6 filters (tab mount screw-post), on a 3000VA
UPS (one on input and one on output) to good effect.
I would suggest spending time looking through the corcom site, they
publish loss tables per the LISN spec for all units. I went through the
site, and then went searching for the better looking parts at
mouser/digi-key/etc for pricing.
The 10EMC3 looked like the best bang/buck for general use at 10amp, the 3
and 6 amp versions have better line to line, but worse line to gnd.
I was going to pickup a batch of 3EMC3 units as well (59db or better
common mode 1-30Mhz), for general lighting/etc use but they were still
about $14 each at Mouser so I decided to wait untill I needed them.
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