[RFI] Motors/controllers and something to think about

Roger (K8RI) k8ri at rogerhalstead.com
Wed Aug 15 23:28:57 PDT 2012

On 8/16/2012 1:40 AM, Jim Brown wrote:
> On 8/15/2012 10:30 PM, Roger (K8RI) wrote:
>> The issue has dealt with specific makes and models with and without RFI,
>> but as PWM is by its nature an RFI generator we need to stop and think
>> about how companies (any company) acquires the motors and speed controllers.
> It is critically important to realize that it is EASY to build a PWM
> system without RFI if you simply pay attention to the fundamental laws
> of physics

I'm still trying to wrap my mind around building switching power 

But when a company contracts out motor controllers they are interested 
in performance and cost.  One thing companies are willing to sacrifice 
for cost is a few complaints and complaints from hams are relatively few 
even if their controllers are RFI generators par excelance.  I seriously 
doubt that "RFI Free" is part of the specifications.

IIRC, Large appliances are not subject to the RFI regulations and even 
if they were, the companies can get by with denying knowledge of the 
problem, passing the buck, and hoping the ham will eventually give up or 
die of old age. It might take years to get them into court and then 
taking them to court takes a very well heeled individual so they again 
have the odds in their favor.  You might even win after spending a few 
hundred thousand dollars and if you were lucky you'd get a new furnace 
out of it, or more likely a new motor and controller. Even then the jury 
will know nothing of electronics and the company can produce "experts" 
who can even confuse an engineer so the odds are again stacked against 
the individual.

Like the current election cycle, they do not care about the truth or 
good engineering practices, only winning.


Roger (K8RI)

  -- keep track of where the current flows, ALL of the
> current, including DC, baseband AC, and RF -- and design your product so
> that it flows in loops that have small cross sectional areas, and over
> wires that don't make good antennas.  It's really as simple as that.
> The most recent edition of Henry Ott's classic text on EMC even has
> chapters devoted to switching power supplies and PWM motor controllers.
> 73, Jim Brown K9YC
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi

More information about the RFI mailing list