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在60950的4.7.2.2 Parts not requiring a fire enclosure中有写/ [1 }' u i3 M" B4 r1 T Y
components in SECONDARY CIRCUITS:supplied by internal or external power sources that are limited to a maximum of 15 VA9 {$ r2 o% Y* y: O$ o5 c3 ^
(see 1.4.11) under normal operating conditions and after a single fault in the equipment% y: c" I# T* ~- i2 N8 F3 j- v. E
(see 1.4.14) and mounted on HB75 CLASS MATERIA,L if the thinnest significant thickness5 h! s& w5 m4 F8 v1 R# a" |6 g3 X
of this material is < 3 mm, or HB40 CLASS MATERIAL, if the thinnest significant thickness of
% \& Q. I3 ~" T7 q" J/ zthis material is ≥ 3 mm;$ ]9 a5 @3 }4 b7 S' u4 A; N3 J/ M, ]
这里说如果PCB板的厚度<3mm,它至少要用HB75 CLASS MATERIA,如果PCB板的厚度>3mm,它至少要用HB40CLASS MATERIA,75的等级不是比40的要低吗?板子越薄应该用较高的防火等级才是啊,怎么是相反的呢?
+ N. {! [9 H5 q8 \& N' t2 s哪位高手能指点迷津啊?非常感谢。 |
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