[RFI] Power Line Bypassing

Dale Svetanoff svetanoff at earthlink.net
Mon Feb 14 20:16:55 PST 2011


This is an interesting thread, as many of us in rural areas have well
pumps.  Jim Brown raises excellent points in his post, below, but I can
tell you that if the problem were with my well pump system, I'd have a very
difficult time doing the by-passing in the most effective manner.  My well
is 315 feet deep, and the pump, according to the well drilling engineer, is
at the 225 foot mark.  It is a 1 HP model that runs on 240VAC, and it is
switched on and off by a simple pressure switch that is mounted at the
pressure holding tank in my basement.  There is no controller, variable
speed drive, or anything "fancy" of the sort.  If I had to install any
by-passes, the closest I could get would be at the well head, 225 feet
above the motor.

It has been my long-held impression that well pumps are inherently
induction motor devices.  With the exception of current spikes at turn on
and especially at turn off (big inductive spike possible), induction motors
are "clean" devices.  I would be interested in knowing if variable speed
drive technology is now used for water well pump motors.  If so, my first
impulse would be to avoid them.  However, I do not know how long my pump
motor will last (it's now a bit over 10 years old), but when it croaks,
they have to pull up all 225 feet of casing above the motor to extract it
and replace it.  If variable speed motors (with the requisite drive
electronics) are now available, I imagine that the well company will offer
that as an option.  Does anyone have info on such systems?

In the case of your friend, try to find out just what sort of well pump
system is involved.  If it is a simple induction motor like I have, then
noise could be coming from an arcing pressure switch or contactor relay (if
used).  There could also be damage to the wiring go to the motor that
results in arcing (due to moisture absorption) in the wiring whenever power
is applied to the motor.  However, if the pump motor really is
electronically driven, then the challenges posed by Jim remain to be solved.

One last comment related to this issue: a very good ham friend lives about
60 miles from me in an area of homes that are spread out in a rather large
development and while each house has its own septic system, all homes in
the development are fed water from a community well.  It so happens that
only single phase AC power is available in the neighborhood, but the water
well pump, which I believe is a 5 HP model, requires 3-phase AC in order to
operate.  The pump house thus has an electronic converter unit that takes
in lots of single-phase AC and converts it to 3-phase for the motor.  It is
fixed at 60 Hz, so it is not producing variable frequency drive for the
pump motor, which sits somewhere down in the well.  My friend has told me
that there have been many problems with the water pump getting shut down by
fault trips on the electronic phase converter during lightning storms, but
the unit is within a block of his house and he has not any RFI issues with
it.  He is active on HF thru UHF, most bands, so he would notice if that
"box" were a problem.  By any chance, is there a phase-converter associated
with your friend's system?

73, Dale

> [Original Message]
> From: Chuck <charlesh3 at msn.com>
> To: <rfi at contesting.com>
> Date: 2/14/2011 9:28:41
> Subject: Re: [RFI] Power Line Bypassing
> Jim:
> The problem here is that it is a neighbor's pump so there's not too much 
> that can be done at that end.
> Considering that it is easier to modify my friend's environment than his 
> neighbor's,  what can you say about power line bypassing? Is 1 kV and .1 
> uF enough for the caps? Best to go common mode and also each side to 
> ground, I assume.
> Chuck
> > Message: 1
> > Date: Sun, 13 Feb 2011 16:26:22 -0800
> > From: Jim Brown<jim at audiosystemsgroup.com>
> > Subject: Re: [RFI] power line bypassing
> > To: rfi at contesting.com
> > Message-ID:<4D5876AE.9080303 at audiosystemsgroup.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > On 2/12/2011 9:05 PM, Chuck wrote:
> >> A friend tells me he has an AC lines conducted noise problem from his
> >> next door neighbor's well pump. In the past, I have heard of people
> >> putting bypass caps onto their service entrance panel.Is his best
> >> to apply bypassing? If so, what is recommended?
> > You didn't say what frequency, or what the noise sounds like.  The first
> > thing I would work on is making sure that the neutral and green wire are
> > not bonded together at the pump. Also make sure that no 120V motors are
> > running between one side of 240 and the green wire.  Both are recipes
> > for noise. Also, try to figure out what kind of motor and motor
> > controller it is.  If it is speed controlled, what kind of controller?
> >
> > The best cure for most conducted noise is a good common mode choke, and
> > the most effective common mode chokes are formed by winding multiple
> > turns of the cable around the "right" ferrite core.  The choke MUST be
> > very close to the noise source to be effective.  Conducted noise is
> > really RADIATED noise -- the wire that conducts it becomes an antenna,
> > so the choke works by killing the current.  You MIGHT do some good with
> > caps at the entry panel, but I suspect that the wiring that's doing the
> > damage is between the pump and the panel, in which case the caps
> > probably won't help.
> >
> > For more, study http://audiosystemsgroup.com/RFI-Ham.pdf  Also, study
> > the tutorial on Power And Grounding for Audio and Video Systems at
> > http://audiosystemsgroup.com/publish.htm   While it's written for those
> > systems, the same laws and rules of good engineering apply, and the same
> > dumb electrical wiring mistakes cause problems at both audio and RF.
> >
> > 73, Jim Brown K9YC
> >
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