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在60950的4.7.2.2 Parts not requiring a fire enclosure中有写$ @/ H- d/ w4 f- z! @. i
components in SECONDARY CIRCUITS:supplied by internal or external power sources that are limited to a maximum of 15 VA( q9 w* c5 [ A7 y7 G9 Q) s9 V
(see 1.4.11) under normal operating conditions and after a single fault in the equipment
3 m' e( P& W$ [(see 1.4.14) and mounted on HB75 CLASS MATERIA,L if the thinnest significant thickness
: r" {$ C V, N. r% m0 p! U L8 j: d1 d7 Rof this material is < 3 mm, or HB40 CLASS MATERIAL, if the thinnest significant thickness of
+ k+ N6 P2 N" k" o( o; ?$ _" J `this material is ≥ 3 mm;
. H! a# l* D& F2 e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?& o$ `; P. m( A$ g4 S
哪位高手能指点迷津啊?非常感谢。 |
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