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引用第1楼yanfenghmm于2010-01-06 09:17发表的 :
$ t% B6 c. c# X( ]& ~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" H. i2 P" M' e
下面是table 4:
8 W9 K, H/ G, F3 u; h( x6 j .
/ t3 w2 E% X% l$ s
( U3 U5 W( F% r) i+ s: a* u6.7.1.1 CLEARANCES
. ~" Q# C$ r* K3 V) b5 f1 _6 bCLEARANCES are specified to withstand the maximum transient overvoltage that can be
% t y, t j7 ?6 Apresent on the circuit, either as a result of an external event (such as a lightning strike, or a
' u/ b! t" V7 ?5 l Zswitching transient), or as the result of the operation of the equipment. If transient
+ s( [1 u$ ?% \! { V4 Xovervoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.4 J4 w+ C4 ]. h! Y `' f! T& n
The value for CLEARANCE depends on
1 X# w8 b& l! d, Z) S: la) the type of insulation (basic insulation, reinforced insulation, etc.);
" M7 g: c' ?" H! w, Q" e' Qb) the POLLUTION degree of the micro-environment of the CLEARANCE.4 l d( Y2 B1 K* z
7 F0 D- w1 s* V' Q) x
6.7.1.2 CREEPAGE DISTANCES
* D/ F0 P% T: o6 B: S4 c- aFor CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses. Q6 ^2 k4 O5 Q7 O- ^$ t# V7 m$ Q
the insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is1 C. m; @. o# I( L
permissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for9 y8 U2 V# O: }1 {# A5 @+ I
CLEARANCE.
1 u! |7 u w# Y+ m/ r. S6 ~% Y4 b; s+ W" q% `* m
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。$ ^; \! H- k$ q x, w) 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+ f+ a* i& B( a2 B7 N( j. R
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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