MIL-STD-461D, How do you maintain EMC w/cabinet open?
MIL-STD-461D, How do you maintain EMC w/cabinet open?
(OP)
I was wondering if anyone has heard of anyone addressing the problem of maintaining EMC when the cabinet that contains EMI/RFI sensitive equipment is open for maintenance or testing. All the Regulations (MIL-STD-461D, Regulatory Guide 1.180, EPRI TR-102323, FCC, etc.) talk about the limits that must be maintained in order to maintain EMC, and to get to that limit you must provide shielding (EMI cabinet). But the issue of opening these cabinets to perform maintenance, while the equipment is in use, is not addressed. Has anyone heard if the industry has or is going to address this issue?






RE: MIL-STD-461D, How do you maintain EMC w/cabinet open?
I do not have any suggestion, but here is a little Java applet which I belive adress your concern:
http://webphysics.davidson.edu/Applets/Poisson/Faraday.html
I'll follow this thread with great interest.
RE: MIL-STD-461D, How do you maintain EMC w/cabinet open?
Short of being able to cut over to a redundant system and isolate or otherwise take the subject equipment off line, it may not be possible to eliminate the EMI with the "normal" enclosure being breached.
I am not familiar with 461D, but does the standard address {or categorically exclude} the issue? Possibly oversimplified, but a solution may be to disable the enclosed equipment prior to access, either by shutdown or bypass. Recognized that it may not be a trivial task.
RE: MIL-STD-461D, How do you maintain EMC w/cabinet open?
I guess I should restate my original question a bit clearer. I was wondering if anyone out there knows why it seems that the EMC community seems to ignore real world situations that require the equipment, within a cabinet, to be tested/maintained while still fully functioning. I work at a nuclear power plant and it is not feasible to just deactivate equipment to perform testing/maintenance (say for example a redundant power supply within a cabinet fails). Not only do standards and regulations “seem” to ignore this; they don’t even cover why it is not an issue. The closest thing I have found that touches on this issue is that the FCC has a disclaimer that manufactures put on their products. “…shall caution the user that changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment” i.e. the equipment has exceeded FCC limits (FCC Part 15.21) It seems to me that if you have to shield equipment to meet EMC limits, that the issue of opening the cabinet should also be covered.
RE: MIL-STD-461D, How do you maintain EMC w/cabinet open?
David Baird
mrbaird@hotmail.com
Sr Controls Engineer
EET degree.
Journeyman Electrician.
RE: MIL-STD-461D, How do you maintain EMC w/cabinet open?
If you can operate a transistor radio with no interference near your equipment, then there should be no problem.
TTFN