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EN 61242中关于线盘的接地电阻的测量中,有如下规定:
" Z8 b# V- J# P! z; P9.7 Internal earthing circuit in cable reels, including any joints contacts and the like, shall be of low
' ]- k+ M* ]" G3 g6 Telectrical resistance., y7 X* b- v/ ]" w. n' h
Compliance is checked by the following measurement which is made after the test specified in Clause 21.
; [ I+ P) B: i w$ P" wA current derived from an a.c. source, having a no load voltage not exceeding 12 V, and equal 1.5 times rated
/ F; F, [- ]) ~; Lcurrent of the cable or 25 A, whichever is the greater, is passed through the earthing circuit.4 `- i9 c2 H' ] f( K8 n8 a% `: r; P( O w, z
The voltage drop is measured and the resistance calculated from the current and this voltage drop.
! e, h7 _1 M7 B; H8 U6 `: }The resistance shall not exceed 0,05 Ω..6 j- x5 i; k; Y. S
8 p8 C7 E! @' q- ?& |测量时,发现如果包含其线盘所带的电缆在内测接地电阻,是绝对大于0.05的,而且主要的电阻产生于电缆本身, % N4 f @2 x4 L/ l; R+ C9 o
我知道在60335中测接地电阻时将电源线是排除在外了的,但是在这个标准里面并没有提到这一点,但是考虑到一般电缆在一定长度下也达不到0.05的限值,那是否意味着这时也应将电源线排除在外呢?但有个问题就是,如果将电源线排除,那么绞线盘的接地电阻还有什么意义呢? D- z2 b2 a# h4 Y* K2 I! A) b* T% v' [
* y" F' x8 p' p' X3 G希望大家能讨论一下,指点迷津..谢谢~!! |
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