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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Circular mil ： ウィキペディア英語版 Circular mil A circular mil is a unit of area, equal to the area of a circle with a diameter of one mil (one thousandth of an inch). It corresponds to 5.067×10−4 mm². It is a unit intended for referring to the area of a wire with a circular cross section. As the area in circular mils can be calculated without reference to π, the unit makes conversion between cross section and diameter of a wire considerably easier. The area in circular mils, A, of a circle with a diameter of d mils, is given by the formula: :$A=\; d^2$ Electricians in Canada and the United States are familiar with the circular mil because the National Electrical Code (NEC) uses the circular mil to define wire sizes larger than 0000 AWG. In many NEC publications and uses, large wires may be expressed in thousands of circular mils, which is abbreviated in two different ways: MCM〔("Power Plant Siting Acronyms" ), California Energy Commission〕 or kcmil.〔("Popular Acronyms" ). NEMA〕 For example, one common wire size used in the NEC has a cross-section of 250,000 circular mils, written as 250 kcmil or 250 MCM, which is the first size larger than 0000 AWG used within the NEC. ==Equivalence to other units of area== Although square mils are rarely used, it is convenient to convert between square inches and circular mils. As a classic example taken from the NEC, a 0000 AWG solid wire is defined to have a diameter of exactly 0.46 inch. Formula 1: Circular Mil :Note: 1 inch = 1000 mils :$d=\; 0.46$ inch = 460 mils :$A=\; d^2$ :$A=\; 460^2$ = 211,600 circular mils :(This is the same result as the AWG circular mil formula shown below for n=-3) Formula 2: Square Mil :$d=\; 0.46$ inch = 460 mils :$r=$ = 230 mils :$A=\; \backslash pi\; r^2$ :$A=\; \backslash pi\; \backslash times\; 230^2\; =\; 52,900\; \backslash pi\; \backslash approx\; 166,190.25$ square mils Formula 3: Square Inch :$d=\; 0.46$ inch :$r=$ = 0.23 inch :$A=\; \backslash pi\; r^2$ :$A=\; \backslash pi\; \backslash times\; (0.23)^2\; =\; .0529\; \backslash pi\; \backslash approx\; 0.16619$ square inches Formula 4: Solving for Circular Mil :$A=\; A$ :$211,600$ circular mils$=\; 52,900\; \backslash pi$ square mils :1 circular mil $=$ square mils :1 circular mil $=$ square mils Formula 5: Solving for Square Mil :1 square mil $=$ circular mils Therefore, the following conversions apply: *To obtain square mils   ⇒ (''# of circular mils'') × 4 ÷ π *To obtain square inches ⇒ (''# of circular mils'') × 4,000,000 ÷ π *To obtain circular mils ⇒ (''# of square mils'')   × π ÷ 4 *To obtain circular mils ⇒ (''# of square inches'') × π ÷ 4,000,000 1 circular mil is approximately equal to: * 0.7854 square mils (1 square mil is about 1.273 circular mils) * 7.854×10−7 square inches (1 square inch is about 1.273 million circular mils) * 5.067×10−10 square metres * 506.7 μm² 1000 circular mils = 1 MCM or 1 kcmil, and is (approximately) equal to: * 0.5067 mm², so 2 kcmil ≈ 1 mm² (a 1.3% error) Therefore, for practical purposes such as wire choice, 2 kcmil ≈ 1 mm² is a reasonable rule of thumb for many applications. When large diameter wire sizes are specified in kcmil, such as the ubiquitous 250 kcmil or 350 kcmil wires, the wire's diameter can be easily determined with the following formula: Formula 6: Diameter :Note: We first convert from kcmil to circular mil :$A=\; 250$ kcmil :$A=\; 250,000$ circular mils :$d=\; \backslash sqrt$ :$d=\; \backslash sqrt$ = 500 mils = 0.500 inch Thus, this wire would have a diameter of a half inch or 12.7 mm. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Circular mil」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.