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  • 學位論文

作業場所電力頻磁場屏蔽控制之探討研究

Study on Shielding of Power-Frequency Magnetic Field in Workplace

指導教授 : 林宜長

摘要


在台灣,一般家庭、工廠、辦公室及電器設備皆使用60 Hz交流電力,本研究的目的是利用60 Hz電力系統所產生的電力頻磁場,並針對電力頻磁場控制的成效進行探討,以避免可能造成健康上的危害。 電力頻磁場最主要的來源與發電、輸電及用電設備有關,其中磁通密度會受到距離、電流以及輸配電線佈設等因素所影響。目前電力頻磁場的控制已知有許多種方法,包括暴露距離增加、導線空間佈設及方向排列及屏蔽等。而本研究主要探討屏蔽方法對磁場遮蔽的改善情形,方法是以導電材料(純銅板、純鋁板)及導磁材料(矽鋼板)當做屏蔽材料,探討對交流電電線所模擬產生源的磁場之遮蔽效果,另外一方面進行一般工廠,營業與辦公場所現場測量及分析,並就其後者之高磁通密度工作場所,以平板狀屏蔽材料進行磁場改善及探討改善後的遮蔽效果。 由屏蔽實驗的結果得知:(1)以平板狀屏蔽材料在測量高度為5cm的長直導線進行磁場屏蔽測試,則屏蔽材料之遮蔽效果大小依序為:方向性導磁矽鋼板 > 非方向性導磁矽鋼板 > 導電性銅板 > 導電性鋁板。(2)方向性導磁矽鋼板擺放應將金屬條紋與磁通密度方向成垂直,可得較佳遮蔽效果。(3)以長直導線及線圈為磁場產生源,且磁通密度約為90 mG時,當採用不同堆疊厚度的鋁板在固定厚度矽鋼板上,其遮蔽效果(S.E.值)隨著堆疊厚度而增加,當堆疊厚度臨界7 mm後,再增加堆疊時則遮蔽效果沒有明顯增加。(4)以電焊方式來處理接縫,雖可改善漏磁現象,但會造成接縫處隆起,不利於屏蔽施工,可考慮以堆疊方式將上下各層接縫處不要重疊。(5)在材料面積約略相同下,圓筒狀導磁材料之遮蔽效果大於正方形筒狀、雙凹形、凹形、平板狀。(6)從環境調查及實場改善結果得知:1. 勞工作業場所如有使用較大的設備如電焊機、變壓器、大型馬達、配電盤及整流器等,其磁通密度會較大,有時甚高達數百mG。2. 一般營業及辦公場所其磁通密度不大,但如果設置地點正好位於電氣室樓上時,則環境的磁通密度會高達幾十mG。3. 在辦公場所之實場改善方面,如可以用平板狀屏蔽材料在地板上進行屏蔽,則將可以以較少施工時間和成本,達到遮蔽效果,如以本研究的兩個實場改善案為例,其遮蔽效果均可達到14 dB以上。

並列摘要


In Taiwan, it was common to introduce 60 Hz alternating current in most places such as households, offices and electrical equipments; this study aimed to investigate on the sources of power frequency magnetic fields and the efficiency of controlling power frequency magnetic fields, in order to avoid detrimental effects of power frequency magnetic fields. Wherever electricity is generated, transmitted or used, power frequency magnetic fields are created. Magnetic flux density is influenced by multiple factors such as distance, electric current and the configuration of power transmission lines, etc. There are various methods to control power frequency magnetic fields, including the extension of distance and space, direction arrangement and shielding, etc. This study attempted to probe for the control parameters of power frequency magnetic fields while manipulating the shielding methods. In addition, we sampled in workplace and evaluated the shielding efficiency of various materials in high magnetic field sources. Results: (1) When testing plane materials in magnetic fields generated by long electric line, the order of intensity of shielding effectiveness is the oriented silicon steel > the non-oriented silicon steel > the copper material > the aluminum material. (2) The shielding effectiveness is the highest when the oriented silicon steel is placed perpendicularly to the axis of magnetic flux density. (3) While using long electric line and loop as the magnetic field source with a magnetic flux density around 90 mG, the thicker the aluminum plate (not exceeding 7 mm), the higher the shielding effectiveness. (4) It could be considered to avoid the magnetic leakage using superimposition of shielding materials rather using welding method. (5) When testing different shapes of permeability ferromagnetic materials in magnetic fields generated by long electric line, the order of intensity of shielding effectiveness is cylindrical > square> double U shaped > U shaped > plate. (6) While surveying in workplace, we found that: 1. The large equipments such as electric welding machines, transformers, motors, power pane land power conditioners often are with higher magnetic flux density (up to 100 - 1000 mG). 2. It is often with less magnetic flux density in business buildings. If there’s a transformer located below a building, the magnetic flux density might be up to 10 - 100 mG. 3. While designing and installing the shield in workplace, we suggest that it is more efficient and economic to use plate shape of shielding material. The shielding effectiveness was more than 14 dB in the two cases of this study.

參考文獻


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