Until a few years ago (or maybe more than a few as I age) National
Electrical Code only required a 3 conductor cable to feed a clothes
dryer. There were two hot conductors (220 volts for heat) and one
combination ground & neutral conductor fastened to the dryer cabinet
which in combination with one hot furnished 110 volts to power the drive
motor. This has changed and the NEC now requires four conductors - 2
hots, 1 neutral, 1 ground. This also applies to electric ranges.
Maybe this sheds a little info.
73,
Ariel, K4AAL
Jim Brown K9YC wrote:
On Wed, 03 Feb 2010 15:27:36 -0600, Stuart Rohre wrote:
The problem may be Variable
Speed Drives in the appliance, lots of modulated semiconductors
controlling the motor for "Green" efficiency. Oh, the laws of
unintended consequences from the environmentalists!
Don't blame environmentalists -- it's lousy circuit design.
There are no guarantees with line filters.
This doesn't sound like a line filtering issue, but it DOES sound
like possibly improper connections of neutral and the power system
green wire, or a missing power system green wire, of missing bonds
of station ground to the rest of what's grounded. These improper
connections could be in the shack or at the appliance.
Some things to check. 1) Make sure that the green wire is bonded
to the chassis at the power supplies, AND where the power supply
is plugged into the AC outlet. 2) Make sure that the chassis
(green wire) is NOT connected to the neutral. 3) Make sure that
your power system ground (green wire) is bonded to everything else
in your station, and that every chassis in your station is bonded
together. 4) Make sure that the common point of your station
chassis bonds (grounds) is tied to the ground rods for your
antenna system, your shack, the power system ground rod, and the
ground for Telco and CATV arrestors.
Look for #1 and #2 at the appliance that is generating the noise.
73,
Jim K9YC
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