I am a bit worried that my pair of Danfoss BD50 compressors are going to put
out a lot of RFI so am working to isolate them by lining the compartment
with foil and putting common mode chokes on the power lines. I have found a
lot of chokes that can handle the current but they come in a variety of
inductances. How do you figure out which value to use? Especially when the
compressor will run at different speeds.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
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Glenn Ashmore wrote:
I am a bit worried that my pair of Danfoss BD50 compressors are going to put
out a lot of RFI so am working to isolate them by lining the compartment
with foil and putting common mode chokes on the power lines. I have found a
lot of chokes that can handle the current but they come in a variety of
inductances. How do you figure out which value to use? Especially when the
compressor will run at different speeds.

hi glenn,

honestly ? trial and error.

that's how i really do it. that's why i keep a lot of toroids and
ferrite rods around, an assortment. i just wrap the wire around a
ferrite rod a bunch of turns, tape it up, and secure it, and that's the
end of that. if i find i have some noise somewhere, i isolate where
the problem is, try some different rods or toroids near the source and
the affected equipment, etc, until the noise goes away. i wouldn't
know a thing about figuring it out upfront. and if it's really a
problem i start covering things in copper tape.

Glenn, on my Danfoss BD35 based Isotherm ASU system the RFI was
unbelievable annoying.
The biggest noise reduction of all the cures I tried was given by a
simple short wire clamped to the copper refrigerant pipe where it
enters the compressor housing and the other end to the battery
negative.
I even went to the trouble of removing the plasic housed electronics
board and remounting it inside an earthed metal box.
Ferrite suppressors, power line filter and other tricks made little
difference.
The compressor is powered by its own dedicated battery.
All the HF radio interference entered the radio via the antenna, not
the 12v connection.
Hope this helps,
Klaus