RF interference in plant

[nmark]

A customer has a 480 3 phase radio frequency sonic weld machine used to join belts.When machine is in heat cycle multiple problems occur.Problem#1 different machine with dc motor variable speed control goes haywire speeds up and down uncontrollably.Problem#2 sonic weld machine has 2 timers that control heat cycle and press that fail intermittently.Problem#3 lights buzz,machine operators radio changes station mainly a nuisance. Sonic weld machine is fed with 30 feet of bus drop cable and makes a transition to EMT at the ceiling.There is a ground rod with #4 copper attached to frame of sonic weld machine and is located 6 feet away from control panel where bus drop cable terminates but it does not connect to control panel just frame of machine.Machine has been operating for a few years I have been told problems becoming more severe but from day one there was interference.Thanks in advance for any suggestions .

 

[sreid]

I'd start by assuming that the interference is caused by conducted RF through the power wiring. Buy some AC Line filters , install them and see if the problems go away.

http://www.corcom.com/

 

[itsmoked]

The machine could have conducted RFI thats getting out as sreid sez. I could expect it to come from the factory with filters. I could also expect an older machine's filters to degrade over time, which fits your scenario. Look for existing filters and replace them.

 

[mc5w]

Consider hard wiring from the busway plug to the machine using galvanized rigid steel conduit. This will attenuate quite a bit of RF radiated out of the branch circuit wiring.

Also, some other parts of the machine especially the work head could be radiating RF. You might have to construct a room with sheet steel or sheet aluminum walls to cut down on radiated RF. If any holes for passing product are done right there should be very little radiated RF.

You probably also need to treat affected equiment with bypass capacitors on signal lines to harden the equipment against radio frequency interference. I have had to do this with a public address system out on the west side of Akron, Ohio because WQMX-FM was forcing its way in. WQMX happens to be located in the next COUNTY so the problem was the affected equipment. I do suspect that WQMX is running California Kilowatts instead of regular kilowatts. ( California Kilowatt is a reference to some radio amateurs having having too much fun with cheap power from Hoover Dam and almost nonexistent presence of the FCC back in the 1940s and 1950s.