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LZ说的要求其实在标准当中是来源于7.2.1的这段话:% a% W6 S6 n7 q" ]9 x
Metal parts of luminaires which may become live in the event of an insulation fault and which
3 u4 _6 ]7 m& Vare not accessible when the luminaire has been mounted, but are liable to come into contact3 q0 c' l& I$ ?; Q) e8 Q% y+ b
with the supporting surface, shall be permanently and reliably connected to an earthing/ Q# ]. k4 F# \( W+ P4 D7 l
terminal.
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" C* H W j2 U2 W: d6 S6 X所以问题的关键在于以下两点:
+ E6 i# o3 c) A& t1、灯具内部的基本绝缘部件会不会与金属支架接触。如果是不可能接触到灯具内部的基本绝缘件,那么其实支架无需接地; E+ s' L- `: W+ b5 _8 K1 I
0 ^9 i+ {. v5 {# f# s" ~1 _/ _2、如果考虑了上述第一点判断支架需要接地,那么是否可以认为安装螺钉+菊花垫片提供了可靠的接地呢?我的理解是要考虑三方面:
, M) b+ B. B) Z, s6 f 2.1 接地电阻测试; 0 O$ C$ Y4 b* g
2.2 满足4.11.3的要求(这里有菊花垫片,可以认为满足了4.11.3的要求); / ]1 j0 p5 B3 [! {% P
2.3 在7.2.1要求‘permanently’永久地连接到接地端子(那么很多机构会认为固定支架的螺钉在安装过程中需要拆装,一次不是一个永久的接地连接。其实这也是合理的,因为你无法保证灯具经过安装后,支架和灯外壳之间还能保持良好的接地连接)- K9 B6 h' j1 e: `5 q/ |
, r7 g3 J- `- ~7 t) c1 G* ?& W至于楼上提及的金属外壳是喷漆或者电镀的其实不是关键,标准当中另有条款规定了:
1 a/ J- {4 x$ d& B2 b+ r9 F7.2.8 Either the screw or the other part of the earth terminal shall be made of brass or other8 L0 Q9 F- f- d) A* r& ^
non-rusting metal or a material with a non-rusting surface and the contact surfaces shall be" G# j- F5 m; `' W
bare metal.
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