In June 2005, VitaTech performed switchgear simulations, during the design phase of a nanotechnology research center in the southeast, to predict the EMF emissions from the switchgear room. Magnetic shielding was recommended for the main switchgear room. The nanotechnology research center design featured 30,000 square feet of clean rooms critical to research and instruction in microelectronics, semi-conductors, materials, medicine, and pharmaceuticals.
It was necessary to shield the main switchgear room in the basement of the research facility to minimize the EMI impact in clean rooms and laboratories designated for research and nanotechnology tools. The elevated to high AC extremely low frequency (ELF) magnetic field emissions from the switchgear room could compromise optimum tool performance.
In February of 2007, VitaTech was contacted by the project General Contractor to install, test and certify an AC ELF (extremely low frequency) magnetic shielding system for the main switchgear room. VitaTech commenced work in June 2007 and successfully completed the shielding project in late August 2007.
The 7,330 square foot AC ELF magnetic shielding system was installed to attenuate the emissions
emanating from two switchgear units and an automatic transfer switch that could effect EMI sensitive tools in the building. The aluminum and low carbon steel plate was fabricated and installed on the floor, walls and ceiling surrounding two 4000 amp switchgears on the basement level of the building.
Shield Design layout over architectural drawings
4000 Amp ATS-43 Automatic Transfer Switch & Switchgear Sources
1500 and 2500-3500 kVA Transformer EMI Mitigation
Transformers are located outside the main building complex. Four 2500-3500 kVA transformers feed the two main 4000 amp switchgears located on the basement level main electrical switchgear room, via four underground duct banks. The duct banks transverse from the transformer vault to the switchgear room underground and outside the main building complex, with the exception of where the conduits tie into the switchgears. It was recommended that the conduits inside the concrete duct bank be composed of rigid galvanized steel (RGS), which provide the highest amount of attenuation (approximately -23 to -26 dB) and would effectively reduce EMI emissions from the conduits.
On July 30, 2008 VitaTech returned to perform a site survey to determine the performance of the magnetic shielding system prior to the commisioning of the building. The AC ELF magnetic flux density levels were recorded after the AC ELF subbasement switchgear room magnetic shielding system was installed and the building energized at 10 to 15% load. Recorded AC ELF magnetic flux density data determined that the EMF emissions were less than 0.1 mG at 3 meters from the shielded switchgear room and met the shielding performance guarantee.
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