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用到PWB需在如下几个条件:
; z$ g' u0 o2 b9 t- F- O( V( s: ]8 Q1 JPollution degree 1:All material groups.
. r+ a; V- l9 h6 R6 N* s' a& l或者Pollution degree 2:All material groups except IIIb.(即PWB的CTI ≥ 175)
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• Insulating material group I CTI ≥ 600;
, ]8 E# ?+ Y7 j5 n9 @• Insulating material group II 600 > CTI ≥ 400;, {& a8 Y/ c+ C2 O5 ]
• Insulating material group IIIa 400 > CTI ≥ 175;
6 J V4 Y9 w2 P# V- L" h- ]• Insulating material group IIIb 175 > CTI ≥ 100.' V7 I5 T' F9 `: ]" U" [
+ k- Z, s7 j( s( t3 l依据以上可以评估是用PWB的绝缘距离还是用Other insulators
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