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在4.6.2章节中有如下内容:+ h: E- Q6 i0 i+ F5 X9 b/ v3 Z
Compliance is checked by inspection and measurement. Except for that portion of the side of, w$ Z" x5 U! J, n! y
a FIRE ENCLOSURE that is subject to the requirements of 4.6.2 (see above paragraph), any one
9 T6 I; @8 _ g7 z) b9 U% o2 Sof the following is considered to satisfy the requirements (other constructions are not/ n3 Z1 @2 w- y* k& g5 M( q
excluded):( L) p4 h7 x; @
− openings that do not exceed 5 mm in any dimension;; `7 h( C% r+ E( D: X- I' O
− openings that do not exceed 1 mm in width regardless of length;
5 F8 n4 l$ u" B− top openings in which vertical entry is prevented (see Figure 4B for examples);
8 A/ d/ t& P0 C− side openings provided with louvres that are shaped to deflect outwards an external
& Y& D c: q/ F4 C" O' Lvertically falling object (see Figure 4C for examples);
4 l# _* C) c+ s" V− top or side openings, as shown in Figure 4D, that are not located vertically, or within a
A. @- W6 N! j0 P" I6 T; svolume V bounded by a 5° vertical projection up to the size of opening L, above bare
7 G' z& r7 Q e" Mconductive parts:4 \, h# t" m+ T3 C% O( f" c7 r4 V
• at HAZARDOUS VOLTAGE, or
6 Q2 [5 v$ ^* B0 E' l% H5 t& p' G• that present an energy hazard within the meaning of 2.1.1.5.$ O7 w1 j! p5 v2 R' \! K
NOTE 2 The examples of Figures 4B, 4C, 4D and 4E are not intended to be used as engineering drawings but are only shown to illustrate the intent of these requirements.
4 N5 Y6 z, b; I3 C- U f2 |我的个人理解是,顶部开孔除了要满足尺寸要求外,孔下面还要有东西挡着,不能垂直或者5度角投影直接投到危险带电体上。 希望我的看法可以抛砖引玉,可以引来大家更深的讨论。 |
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