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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:! Y9 n: c3 Q9 G0 r: w: l
Metal parts of luminaires which may become live in the event of an insulation fault and which: Y/ C# ]9 G+ i. ` h
are not accessible when the luminaire has been mounted, but are liable to come into contact
8 T P! N# X, g6 l* \9 [8 {with the supporting surface, shall be permanently and reliably connected to an earthing7 D* a+ d, l6 S# f
terminal.
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' [- s& D8 B( \8 N6 w0 s) e所以问题的关键在于以下两点:4 s1 T! ^/ { S. k, k4 v1 x
1、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;
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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:
) a E4 `0 N$ ]" R1 h9 u 2.1 接地电阻测试;
% ~% ]- P. ?. N1 s 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); 9 G4 C% r( S/ T
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); w' R" @1 E- S! e
/ z' \, y7 Y5 n$ E) \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:
5 |: c$ G$ x8 u: c8 P6 h' r8 z7.2.8 Either the screw or the other part of the earth terminal shall be made of brass or other0 R; P( y- N+ V9 \( _% \' @
non-rusting metal or a material with a non-rusting surface and the contact surfaces shall be: p; L; P) t o9 u6 k5 M
bare metal.
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