|Topic Review (Newest First)|
|03-10-2006 06:13 AM|
I believe that Danfoss has a newer reduced EMI (BD35) unit, incorporating both radiation shielding and conductive filtering.
Richard Kollman < http://kollmann-marine.com >has an excellent forum, where he provides detailed refridgeration answers. I
|03-10-2006 05:49 AM|
Radiated vs Conducted Noise
I’m not expert in RFI Shielding, nor EMI Suppression, so take the following /w a grain of salt.
Motors can cause one or both of two types of noise: Radiated RFI& Conductive E.M.I.
Except for the refrigeration motors, which can definitely produce EMI, most of the motors aboard (ie: Bilge Pump) cause RFI, sometimes known as spark-gap noise. Tackling EMC is daunting, whether suppressing or shielding (or both).
A Faraday Cage will only shield against radiated RFI, not conducted EMI noise. An effective shielding cage is very difficult to build, and I wouldn’t recommend them in this application.
Conducted interference travels from the source (ie: Refer’ Motor) to your radio or tuner over the DC wiring. The wiring acts as an antenna, actually funneling the radiated signal to the location where it can cause the greatest interference.
When you encounter a really stubborn interference signal, you might use a toroid coil, or Ferrite Beads, wrapping BOTH the positive and negative wires as close to the motor, or other device, as possible. Use a (40 - 60 micro farad) capacitor across the positive and negative motor leads. You must contain the emission as near the source as you possibly can. Common-mode chokes are wound in a manner that produces a high impedance to signals appearing in-phase on both windings while having little effect on differential- or normal-mode signals.
|03-09-2006 11:32 PM|
|camaraderie||If you do decide to build a cage...be sure to also use foil on the thermostat/control knob switch as well as the main unit!|
|03-08-2006 05:31 AM|
Four years ago I replaced my 13 year old Adler Barbour Cold Machine with a new unit. I was very disappointed to discover the RFI from the control module. My question to the tech support folks was answered ... they were aware of the problem but did not have a solution. They suggested a Faraday cage (as drwil has posted) ... i.e. complete shielding of the unit with copper mesh or the like. Too difficult for my installation so it's now standard procedure to turn off the unit before doing email, talking on a net, or copying weather faxes. The biggest problem is remembering to turn it back on!
As an aside, my 4 year old unit developed a leak where, the repairman says, all of these units will eventually leak. It's at the junction of the copper tubing to the aluminum tubing at the back of the evaporator. Electrolysis does it's thing here but the repair is simple ... La-Co epoxy sealer (sold for this purpose by Markal http://www.laco.com/ProductDetails.aspx?ProductID=45) .. but it must be done with pressure on the system. It's quite brittle after curing so an epoxy coating over that with the metal repair kits keeps it from moving and breaking.
Tell your friend the bad news ... another case of the marine industry flogging a product and forgetting the customer. If marine products were designed by other than landlubbers we might have a better choice of gear.
|02-23-2006 03:25 PM|
RF quenching solution
If all else fails, try a Faraday cage. Surround the offending unit with a "box" of fine mesh copper screen. This will knock out RF and still allow air circulation.
|09-06-2000 08:45 AM|
Adler-Barbour Cold Machine
Would shielding the unit with (thin)stainless sheet metal work??
|08-26-2000 06:53 AM|
Adler-Barbour Cold Machine
I am trying to help a friend of mine on a yacht in the South Pacific.
He has a Adler-Barbour Model PB-331-134 with a Danfoss Electronic Module which turns out to be a world class RF generator. He cannot operate his Ham radio without turning off his refrigerator. Other boats nearby, with A-B machines report the same problem.
Has anyone had the same problem and found a solution or work-around?
Thanks, Charles Gunthorpe