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如果强制要求是PIII的话,一般特殊标准会指出;& N+ r3 S% G. i2 K
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;) u# }6 h% S, Q. g6 o9 W
# |8 _- p9 c9 ~( s3 y/ _' K/ N: w5 }2 ^但是具体还是要看使用环境,见Annex M.
9 U2 F. ^: W; D) R- s% K– pollution degree 1: no pollution or only dry, non-conductive pollution occurs. The pollution
$ ?3 H3 C$ k0 V! x+ I. }# Xhas no influence;
. v9 W, J- T0 |0 ?4 G– pollution degree 2: only non-conductive pollution occurs, except that occasionally a$ N$ x0 Q5 [0 n) x6 h2 a0 F6 x/ S
temporary conductivity caused by condensation is to be expected;
% y( G c% \' n! v/ O2 L– pollution degree 3: conductive pollution occurs or dry non-conductive pollution occurs that
0 I! Z2 x% U# o! w' U3 gbecomes conductive due to condensation that is to be expected;
( ^5 T! t5 d5 H+ T3 Y# y
' K( |, ~( }$ A7 N# mBTW,密封环境才可以判PI |
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