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用到PWB需在如下几个条件:1 ]$ e( {; J7 {% o0 o
Pollution degree 1:All material groups.
, [- q4 B- u+ Z0 a或者Pollution degree 2:All material groups except IIIb.(即PWB的CTI ≥ 175)% ~- s9 W* ]) G' l! O% q
2 X: R; v" J3 b1 M; M+ O• Insulating material group I CTI ≥ 600;) F, |! _8 e& [# u* e. O
• Insulating material group II 600 > CTI ≥ 400;
5 a, F1 m; ]7 H$ \) A$ ~7 ^• Insulating material group IIIa 400 > CTI ≥ 175;8 L+ @0 U8 O, ~) O
• Insulating material group IIIb 175 > CTI ≥ 100.
) d) N9 z5 X8 D7 Q* p, O; T) N! W B5 M& q; P
依据以上可以评估是用PWB的绝缘距离还是用Other insulators* _( \ F0 j9 p! K" J6 }8 i, O
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