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用到PWB需在如下几个条件:
% D& \* F$ k7 P+ t5 _Pollution degree 1:All material groups.
# H1 H9 L: S, r) u9 t或者Pollution degree 2:All material groups except IIIb.(即PWB的CTI ≥ 175)
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9 v* ^9 N6 i7 ^/ T' A% P3 z3 f• Insulating material group I CTI ≥ 600;5 t" W- v$ a) ^4 t# O' i
• Insulating material group II 600 > CTI ≥ 400;( L+ {+ f8 |) y6 B) E- ]8 O+ i o
• Insulating material group IIIa 400 > CTI ≥ 175;) K/ ?9 A* f3 C# F6 w" w% S
• Insulating material group IIIb 175 > CTI ≥ 100.
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7 C7 f' h* C1 Q依据以上可以评估是用PWB的绝缘距离还是用Other insulators* Z5 y* M' F6 L. e2 ^
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