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如果强制要求是PIII的话,一般特殊标准会指出;
' y8 Z3 C( P8 w如果没有,绝大部分可以判PII,特殊情况,例如有碳刷的串激马达或者直流马达(考虑工作中产生碳粉),有蒸汽通过有有电气部分的内部结构的(部分2件套的水壶),即使特标没要求,也都应该判PIII;
b \1 K; Q4 H5 c: ]
" ~0 N( \. w( r2 {; ^: ~# ?8 v* }但是具体还是要看使用环境,见Annex M. ! c% u( S, Y, d- D0 Y
– pollution degree 1: no pollution or only dry, non-conductive pollution occurs. The pollution1 N. K+ i" W$ z7 O. ^) h; N1 L7 x9 F
has no influence;& |. O5 w' E+ N( n+ F1 q* m
– pollution degree 2: only non-conductive pollution occurs, except that occasionally a' X! e. M& p) W6 L
temporary conductivity caused by condensation is to be expected;; L+ a2 J" q/ r, b# Q H
– pollution degree 3: conductive pollution occurs or dry non-conductive pollution occurs that
, C, q; D/ _3 V6 nbecomes conductive due to condensation that is to be expected;/ t* |0 ~7 S) _) u
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BTW,密封环境才可以判PI |
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