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在60950的4.7.2.2 Parts not requiring a fire enclosure中有写
) _! g& x, @/ @( P( L# i/ W5 f# D. Vcomponents in SECONDARY CIRCUITS:supplied by internal or external power sources that are limited to a maximum of 15 VA
! S# M: R5 i( W" Y) _- ^8 ?- v(see 1.4.11) under normal operating conditions and after a single fault in the equipment
! X+ P. x( x4 E$ x; A1 K" z) d(see 1.4.14) and mounted on HB75 CLASS MATERIA,L if the thinnest significant thickness
, c. [" Z8 K/ a) x, Hof this material is < 3 mm, or HB40 CLASS MATERIAL, if the thinnest significant thickness of
6 h* |* i+ K* ]0 E* A4 Athis material is ≥ 3 mm;9 e1 p" }7 G3 f1 b) S( e3 c) k9 p
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?
! l, f0 ^) O7 \8 L哪位高手能指点迷津啊?非常感谢。 |
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