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在60950的4.7.2.2 Parts not requiring a fire enclosure中有写- I4 W0 |$ x' |% ]3 V0 ^- [
components in SECONDARY CIRCUITS:supplied by internal or external power sources that are limited to a maximum of 15 VA
; q& ?0 Z6 c0 ?, i0 Y7 X(see 1.4.11) under normal operating conditions and after a single fault in the equipment
6 |1 W/ c% H. ?0 r9 }6 a(see 1.4.14) and mounted on HB75 CLASS MATERIA,L if the thinnest significant thickness0 v% T: i8 u. V9 ?# b+ X1 c8 J
of this material is < 3 mm, or HB40 CLASS MATERIAL, if the thinnest significant thickness of
1 N# k4 }8 ?: @5 k& f, `6 H. s" pthis material is ≥ 3 mm;
( E$ Z; c8 H" W v. `7 ?0 @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?$ h9 n+ U6 U2 V9 N) \: N
哪位高手能指点迷津啊?非常感谢。 |
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