Magnetic fields around low voltage panels
Magnetic fields around low voltage panels
(OP)
I have an electron microscope installation I'm working on and one of the requirements is that any magnetic fields in the vicinity of the unit be less than 1.0 milliGauss at 60Hz. There are four 208/120 Volt 3-ph panelboards located on the corridor side of the room partition. The panels are steel and all raceways are steel. Distance to the microscope from the panels is about 10 feet.
If anyone has experience with measuring the magnitude of magnetic fields around panels or knows of IEEE papers on the subject I would appreciate your input.






RE: Magnetic fields around low voltage panels
http://www.emf-data.org/related-projects.html
You might also search EPRI website.
1 milligauss seems pretty low. Your local electric utility may have instruments available for doing field measurements. Make sure you take measurements when panels would be heavily loaded. Fluorescent lights could also be a problem.
You may need to think about moving locations, or applying some additional shielding.
RE: Magnetic fields around low voltage panels
<nbucska@pcperipherals.com>
RE: Magnetic fields around low voltage panels
Two condensed online references are
http://www.ce-mag.com/archive/1999/sepoct/Casamento.htm...
http://www.microwavenews.com/EMF.html
You might contact Don Deno at Electrical Field Measurements Co in Stockbridge, MA for paper articles and basic instrumentation for Magnetic Field surveys. {DenoD@RNetworx—no web site}
RE: Magnetic fields around low voltage panels
http://www.thomasregister.com
and type Gaussmeters under Product or Service, which will return 54 companies to approach to for the gaussmeter. Electromagnetic field around panels changes with the load, harmonics, voltage spikes, etc. over a period of time.
RE: Magnetic fields around low voltage panels
Shielding can be used as an expensive last resort, but relocation is the usually easier. See http://www.amuneal.com/
RE: Magnetic fields around low voltage panels
Wholesale replacement of CRTs with LCD monitors were a very good solution for one office with excessive power-frequency magnetic fields. The building owner compensated a tenant group for a significant portion of replacemnt expense.
RE: Magnetic fields around low voltage panels
http://home.t-online.de/home/electrosmog/emf-exposure-l...
David Baird
mrbaird@hotmail.com
Sr Controls Engineer
EET degree.
Journeyman Electrician.
RE: Magnetic fields around low voltage panels
For some basic info, see
http://www.magnetic-shield.com/start.html
http://vitatech.net/emfshielding.html
RE: Magnetic fields around low voltage panels
Obviously, the largest offenders will be high-current carrying circuits and switchboards/panelboards, but, after many EMF surveys from DC to 60Hz, I have found that one of the most common but overlooked sources are CRTs themselves. Some of the older units can have over 100mGauss at a distance of approximately 1'.
RE: Magnetic fields around low voltage panels
RE: Magnetic fields around low voltage panels
You may want to consider hiring someone to do a survey. Some electrical testing companies can do it and almost all shielding designers and engineers offer this service. I have had experience working with one of the the aforementioned engineers mentioned in the above posts. Intereference from can defintiely be a problem with sensitive electronic equipment. In my experience though it was costly, but attainable to shield to the 1mg level. Optimal design might include relocating the panel or other equipment causing the interference as opposed to shielding. It may be more cost effective. It may also be feasible to put only a small shield around the equipment. In my particular case I was invloved in a project in which entire utility vaults a building were shielded. It certainly an after thought in the design and not something that was considered. Strategic placement of the equipment is the optimal solution.