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引用第1楼yanfenghmm于2010-01-06 09:17发表的 :0 _9 C% ?. o8 y0 H" T
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2 B* X6 x, q" Q- r& ^# ^; N; f
下面是table 4:3 H3 W8 z2 Z( }9 v7 W
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8 X/ p) v" F& Y. ?' U; K- V6 I9 D7 l9 m
6.7.1.1 CLEARANCES( g" g9 w# _9 p7 ]0 q, r3 G
CLEARANCES are specified to withstand the maximum transient overvoltage that can be5 \, g+ }1 }, }$ C
present on the circuit, either as a result of an external event (such as a lightning strike, or a! A5 h% W5 H( V- B/ g! [$ ]
switching transient), or as the result of the operation of the equipment. If transient; j7 g; j1 M- R$ j# h' _
overvoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.
5 y; p8 }% r u$ [, JThe value for CLEARANCE depends on
% G4 d6 S( H6 e ea) the type of insulation (basic insulation, reinforced insulation, etc.);
, f+ N+ I \# U4 H% a8 Sb) the POLLUTION degree of the micro-environment of the CLEARANCE.5 Y* A$ J/ I4 [7 h) `
5 O# `" I) g$ e4 |5 V6.7.1.2 CREEPAGE DISTANCES0 r5 e4 R2 t3 Q" Z/ z5 Y b/ P
For CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses
% s! O, ^/ S* T3 Y% dthe insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is
( R/ r" ^5 R6 C0 U5 wpermissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for% ?% F1 n" e; d
CLEARANCE.
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# V! r* Q/ p9 @ 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。% D4 ^+ B8 h) @
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' n( Q( n3 m6 z0 T
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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