[LCC] RFI problem from our Texas connection

[Marshall Stewart]

The company I work for (Eaton - Cutler-Hammer) uses PWM in AC VF drives to
control the speed of AC motors.

 

73,

Marsh, KA5M

 

  _____  

From: lcc-bounces at louisianacontestclub.org
[mailto:lcc-bounces at louisianacontestclub.org] On Behalf Of Dan Edward Dba
East edwards
Sent: Monday, August 02, 2010 2:57 PM
To: Randy Prewitt
Cc: lcc at louisianacontestclub.org
Subject: Re: [LCC] RFI problem from our Texas connection

 


hey randy

 

thats interesting. i thought PWM's (pulse width modulation) were just used
for 

 d.c. motors....they're putting d.c. motors in washing machines now ??

 

they ( pwm's ) DO make a nasty looking square wave, which contain many

many many frequencies...

 

curious......or maybe i'm just stupid and dont know about PWM's & ac
motors...

 

73, w5xz, dan

 



--- On Mon, 8/2/10, Randy Prewitt <ranprew at foxsale.com> wrote:


From: Randy Prewitt <ranprew at foxsale.com>
Subject: [LCC] RFI problem from our Texas connection
To: lcc at louisianacontestclub.org
Date: Monday, August 2, 2010, 7:14 AM

Forwarded from our Texas friends. Two separate exchanges.

randy  K4LJA in Monroe, LA

----- Original Message ----- Sent: Sunday, August 01, 2010 9:16 PM
Subject: Re: FW: RFI problem


> I also monitor the RFI reflector and that sounds correct to me.  If your
rfi is low level or can be worked around count yourself lucky.  I would
think your machine would have a low usage.  It will be interesting to hear
what Whirlpool has to say.  I've worked with Mike Gruber  at ARRL when I was
involved with Vectren Energy.  Good man.....
> 
> Skip
> 
> On 8/1/2010 20:45, Randy Farmer wrote:
>> 
>>> I contacted ARRL about my washing machine RFI problem and received the
following response.  My RFI isn't all that bad, so I'm not sure I'm going to
do all of this stuff, but I thought it might be of interest to some of you.
>> 
>> I'm subscribed to the RFI reflector, and there have been numerous
messages regarding washing machine RFI complaints. Most the newer "high
efficiency" models use DC motors with variable speed controls. The designers
know how to make PWM motor controls cheap, but they don't know squat about
EMI. The haphazard wiring, with no common ground point (if there's one at
all) make them dandy radiators. Seems that one of the Korean brands, maybe
Samsung or LG, has a reputation of being pretty clean. Whirlpool is reputed
to be the worst.
>> 
>> As I recall, the consensus of the experts on the RFI reflector is that
the FCC doesn't regulate "appliances" at all. If they don't now, they're not
likely to start any time soon. Welcome to the 21st century.
>> 
>> 73...
>> Randy, W8FN




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