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引用第1楼yanfenghmm于2010-01-06 09:17发表的 :
1 ^( W/ Z; S0 ^% h% }7 y1 q9 P# U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9 ]$ Z" O& a8 j2 g# i% y3 m
下面是table 4:
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+ _) G! O% E1 Y2 f" G
6.7.1.1 CLEARANCES
- J1 T# n$ K, a) ]3 ?) ]CLEARANCES are specified to withstand the maximum transient overvoltage that can be
3 [8 l x- Q' R/ Z- ^ B6 g( O. C3 fpresent on the circuit, either as a result of an external event (such as a lightning strike, or a' L+ h4 D! }5 |, d S
switching transient), or as the result of the operation of the equipment. If transient2 k: h3 Y- l$ R
overvoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.( i0 q Q8 X6 e" [( a9 I
The value for CLEARANCE depends on: J7 G0 y+ c& t7 n* E- c, U
a) the type of insulation (basic insulation, reinforced insulation, etc.);
4 J$ O! q3 J' Z; E0 ub) the POLLUTION degree of the micro-environment of the CLEARANCE.
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/ N9 z" l% w# L6.7.1.2 CREEPAGE DISTANCES6 T) W7 c, G5 X$ C, I
For CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses
( _/ i0 Z; J: }the insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is$ v u. P& a, x
permissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for _( X" F$ W' p ~' J5 G7 j
CLEARANCE.
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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。4 P9 u* M: ~0 W
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
8 r* G8 ?- h' C% i# v% v( d( g7 pa.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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