|
|
楼主 |
发表于 2011-11-12 10:31
|
显示全部楼层
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。 " J7 V) r/ x+ }
2 R/ D" l G* Z( d
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？
' Y6 b* O, ^% q( q
! f& b. H9 q) j3 C0 K% s标准也是有明确从插脚算起来的： * j. z9 t x+ m( e
65.1 The resistance of the grounding path between any metal part that is required to be grounded (see
% z8 Z. d6 l+ m1 ^35.1.1) and the equipment grounding terminal or lead, or the point of attachment of the wiring system, or ; v6 g8 o) U% M# W0 ~
| the grounding blade of an attachment plug |
, shall be no more than 0.1 ohm.
- o, ^" }9 _2 @! Q& a* [# b: X& N% Q& K# c
当然标准也在变，不一定从插头算起（UL1573）： : u" ~" Z2 N6 e) Q4 p$ u3 X1 n
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
/ z1 I4 A: G) k% M
UL153： # z+ u& [! f# R5 [' Z
136.2 Test method ' K" ?6 w1 ~5 Z
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).
- N2 u0 Z# x* k8 P" a3 j
$ @; I" b1 ^: ^+ Q/ s2 ?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？; a. l3 r# O4 R4 t# x) q
) Q9 V+ X! [- Q$ M0 d" c |
|
|关于安规|小黑屋|安规QQ群|Archiver|手机版|安规网
( 粤ICP13023453-10 ) 
窥视卡
雷达卡
发表于 2011-11-11 17:16
显身卡
发表于 2011-11-12 12:12