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发表于 2011-11-12 10:31
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没错，接地电阻测试时大家都默认可以不包括电源线的，那是认为三根线（L、N、G）阻值一样大，在这种失效模式下阻值过大其实没有关系。测试仪器其实是带校正功能的，直接短路两根绿色的线归零就去掉了测试设备的阻值，大家无需担心测试方法的问题。 3 i8 i6 D E2 I ?* {$ O
! R7 F7 J/ @2 f+ `$ ]: l. |7 ]) F但是这根电源线很蹊跷，用电桥法测试三根电线确实也是毫欧级，但是带载25A测试达到0.178欧，而L和N线带载25A却达不到这个阻值，你认为这根线的问题在哪里？
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4 n5 f8 R, ?& X1 q! X. D标准也是有明确从插脚算起来的：
* B$ \2 |& X$ j' o65.1 The resistance of the grounding path between any metal part that is required to be grounded (see
6 y. x7 c5 ?. I# ^ m/ I- @( ^7 w+ r35.1.1) and the equipment grounding terminal or lead, or the point of attachment of the wiring system, or + v N- W5 C0 T% A* b- o3 W2 T: W
| the grounding blade of an attachment plug |
, shall be no more than 0.1 ohm. ! R: ]+ [/ H/ S+ H) x5 D
' f8 j1 ]/ d* s( s6 E: b% t当然标准也在变，不一定从插头算起（UL1573）：
) p- E. i' I& p1 x2 X& I/ I! A( L7 ^36.4 When an indicating device of the type described in 36.3 does not indicate continuity of the grounding circuit, an alternating current or a direct current of at least 25 amperes from a power supply of not more than 12 volts is to be passed | from the point of connection of the equipment grounding means to a point |
| in the grounding circuit and the points |
. The resistance in ohms is then calculated by dividing the drop in
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UL153：
+ I% f' q% c6 l c& F3 [136.2 Test method ) l# d1 }6 r/ v0 x, L, n
136.2.1 The impedance between the point of connection of the equipment-grounding means and any other accessible metal part required to be grounded, shall be determined by applying a current of 25 amperes – derived from a 60 hertz source with a no-load voltage not exceeding 6 volts – | between the grounding connection and the metal part in question |
. The resulting impedance is calculated by dividing the value of the measured voltage by the applied current (25 A).
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- y4 e$ k; k5 L, O* {8 U% @大家考虑一下，为什么厂家要把地线做成与L和N电阻不一样？
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