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用到PWB需在如下几个条件:
# V/ h! c, P, q3 N- x W" ?Pollution degree 1:All material groups.2 k$ z8 r9 r' i& }# A
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;+ w* m, P3 u/ x. l2 J
• Insulating material group II 600 > CTI ≥ 400;8 t& u: v9 S, d5 Y. l! ?, ?* W, y
• Insulating material group IIIa 400 > CTI ≥ 175;
1 ?+ x; E2 |: i( {• Insulating material group IIIb 175 > CTI ≥ 100. r, q9 u3 ]& r
' K# ?* M% s: Y/ x) G. {* S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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