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发表于 2010-1-6 09:40
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引用第1楼yanfenghmm于2010-01-06 09:17发表的  :" x. z, \' V, \
标准应该有具体要求吧。 文字的要求有时是含混不清的,要看读者的理解呀
0 D5 w% a6 w) ~& v8 P下面是table 4:
5 X) s7 o$ x: {, I! w .
! Q+ S: s8 ~- [
/ v: o% G: m* I9 F; ?) j6.7.1.1 CLEARANCES
( U2 M6 X9 q n1 v. O7 d' [* r6 KCLEARANCES are specified to withstand the maximum transient overvoltage that can be
' S$ T+ l& G: hpresent on the circuit, either as a result of an external event (such as a lightning strike, or a- C* p' s1 ~4 {) z
switching transient), or as the result of the operation of the equipment. If transient
& ?4 f/ p$ A) [overvoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.
: I9 S8 s1 a6 j& Q8 NThe value for CLEARANCE depends on$ E9 M' B% v( a
a) the type of insulation (basic insulation, reinforced insulation, etc.);
$ I5 e) ^5 L O4 |2 Z0 Lb) the POLLUTION degree of the micro-environment of the CLEARANCE.9 z$ I4 M5 F9 d0 d5 U0 y9 a, M
2 H$ `* }9 k4 t8 y
6.7.1.2 CREEPAGE DISTANCES
/ E) f9 E, |" X d% S7 D5 pFor CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses
o# y9 V/ c8 o+ n8 Uthe insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is
/ E: @4 Y: j3 l" m+ [; F; Xpermissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for
$ U- o8 u% F3 ~, K% b" rCLEARANCE./ X. `7 S* I) b
, P* d! I- m a* w" m$ B& X
一般而言电气间隙被设计为耐受最高瞬时过电压,经常会考虑工作电压峰值带来的影响;而爬电距离被认为是耐受工作电压有效值的。* ?. V: L/ J/ [: O0 m
从上面两大块文字中,该标准中6.7.1.1看不出电气间隙要考虑工作电压(peak or rms)的要求,但6.7.1.2爬电距离明确说明要考虑工作电压。而table 4中第一列表头只写了"Voltage line-toneutral# G% M8 S* v0 ^0 [, l' ^
a.c. r.m.s. or d.c.",也没有提"working voltage"。所以实际查表时我就犯难了,到底如何操作呢,请高手指教! |
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