Magnetic field shielding

Pao Yue-kong Library Electronic Theses Database

Magnetic field shielding

 

Author: Tsang, Wai-bong
Title: Magnetic field shielding
Degree: M.Eng.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
Electromagnetic fields -- Health aspects.
Electromagnetic interference.
Magnetic shielding.
Department: Dept. of Building Services Engineering
Pages: 95 p. : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2117602
URI: http://theses.lib.polyu.edu.hk/handle/200/3334
Abstract: The aim of this research is to demonstrate the effectiveness of shield application on current carrying electrical conductors. Shield material is limited to aluminium sheets. Gaps, which are commonly seen in actual electrical installations, are included to enhance the practicality of the study. An extensive literature review was performed to understand the field, scope and depth of studies that had been carried out by other researchers in the subject. Besides carrying out experiments in the laboratory, various supplementary works are also essential to maintain the integrity and credibility of this study: examples include designing laboratory setups and subsequently writing up experiments proposal; utilising computer programs to give theoretical values and compare against the measurement results. With the help of precise computer simulation to spot inaccurate measurements and reassure the accurate ones, the effectiveness of shield is identified. At the completion of this project, this research could provide the industry with practical shielding effectiveness information and minimum coverage of shield required for effective shielding. It is identified that a roughly 10 % reduction in magnetic field strength could be achieved with the use of aluminium planar shields, where gaps play no significant role in reducing the overall shielding performance, as no magnetic flux leakage is observed. However, performance will deteriorate at around 10 cm perimeter region, which should be considered during shield designs by allowing extra coverage area in addition to the conductor size alone. The aluminium sheets (1 mm thick in this study) are also less effective when the magnetic field strength is reaching 10 milli Gauss or below, but at this level, impact on human health and sensitive equipment are both minimal.

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