[RFI] Help on speed drive motor controller RFI

[Leigh L Klotz, Jr.]

I have a Whirlpool Duet washer with a variable-frequency AC motor 
controller made in Germany.  Another ham has the same controller in his 
Sears washer and quieted it with a brute-force filter and ferrites.  He 
and I both wrote articles on eHam.  I put in ferrites but have not yet 
put in the filter as I want to get the case and ground bonding done 
right and the unit is very heavy and in an awkward location.  Moving my 
antenna, moving the easher, better grounding, ferrites and re-routing 
the power and control cables all helped reduce by about 40dB.  The 
filter would probably take it down more.  Search eHam and this list for 
pix.
73,
Leigh/WA5ZNU
On Mon, 29 Jan 2007 2:01 pm, Juan EA5RS wrote:
> Thank you very much for all responses, both direct and thru the 
> reflector.
> It was very enlightning to hear your opinions.
>
> When I said the speed controller did not have any RFI filters fitted, I
> meant it was not using the separate, optional RFI and "dV/dt" filters
> offered as options by the manufacturer. I actually don't know if the
> controller has any type of RFI filtering inside.
>
> I have to agree that even performing to EMC standards, and I am sure 
> this
> one is not, the RFI from this controller is absolutely unacceptable for 
> weak
> signal reception.  Just from the beginning I anticipated this would be 
> a
> very tough RFI problem to deal with due to proximity and tremendous QRM
> levels.
>
> That is why, to be practical, it seems to me that the only feasible 
> total
> cure is to avoid the speed controllers all together, and this is going 
> to be
> my goal. According to an Hydraulic Engineer I have been consulting 
> with, the
> pressure controlled system and specifically the pump motor does not 
> demand a
> variable speed drive at all, and a simple relay "on-off" controller 
> could do
> the job and this would completely eliminate the problem. Now I need to 
> be
> persuasive with the contractor and my neighbours.
>
> Still, the doubt remains why this controller generates so much QRM 
> while
> those others I am sure also exist near my antennas (i.e. elevator motor
> controllers) are apparently QRM free. I also would like to know if the 
> fact
> the controllers supply currents near square wave is a real requirement 
> for
> motor control or it is just the way it is being done. I have a hard 
> time
> believing slightly rounding the waveform could impair motor 
> performance.
>
> 73,
> Juan EA5RS
>
>
> -----Mensaje original-----
> De: rfi-bounces at contesting.com [mailto:rfi-bounces at contesting.com] En 
> nombre
> de Tom Rauch
> Enviado el: lunes, 29 de enero de 2007 11:37
> Para: Ian White GM3SEK; rfi at contesting.com
> Asunto: Re: [RFI] Help on speed drive motor controller RFI
>
>>  Please read what was actually written, Tom.
>
> The EA5's post must have choked in a spam filter, but  my
> points are twofold.
>
> 1.) even when the supply meets or exceeds FCC and CE specs,
> it can cause bad RFI problems.
>
> 2.) even if we don't see an obvious filter it may have one
>
> I certainly agree a unit that fails CE and is labeled CE in
> theory gives a complainer great power, but I can tell
> everyone from first hand experience units that meet or
> exceed CE can cause slight problems a mile way and can be
> devastating within a few hundred meters.
>
> There is a chicken farm about two miles from that has a
> controlled made in the Netherlands that does pass CE and FCC
> but still has birdies several dB out of my noise on 160
> meters.
>
> I worked on good three phase controllers at another location
> that were several hundred feet from the receiving antenna
> and caused bad problems in a moderate background noise
> environment.
>
> It is virtually impossible for most people to test for CE or
> FCC compliance or to know if there are really filters in the
> unit (if they are necessary to pass). The bottom line is if
> it bothers the radio... and a device that passes certainly
> can be a problem. In such cases, and they are common,
> filters from the manufacturer often are useless.
>
> 73 Tom
>
>
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