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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  :
/ Z1 G6 k; Q# L8 u2 N" H3 c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 4 e( O& N) z) y) O4 s3 a, F
下面是table 4:# V" G* ?3 e9 K
.9 |/ F, _+ U' h3 ~: s* E
) u$ P) l5 ?0 d: T# {0 M& E8 Q6.7.1.1 CLEARANCES
) z. T) _: K6 B, c/ @# ?$ G; ~' NCLEARANCES are specified to withstand the maximum transient overvoltage that can be
' D: `4 Q+ k+ Vpresent on the circuit, either as a result of an external event (such as a lightning strike, or a# T" P3 H1 }: I9 v: L- i; ]+ P
switching transient), or as the result of the operation of the equipment. If transient
# i9 K Y2 ?8 l0 J; N2 Y4 M( povervoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.7 ~, C/ @* N% a$ b
The value for CLEARANCE depends on& o7 `% S3 z2 }2 U; D
a) the type of insulation (basic insulation, reinforced insulation, etc.);' X) K# s/ c6 G. H
b) the POLLUTION degree of the micro-environment of the CLEARANCE." j2 ~1 }: z' j" E, T. N0 B6 c1 p: n
' I4 j X) r3 C# h0 J% T6.7.1.2 CREEPAGE DISTANCES' r9 F% ~6 j3 j! \/ n9 ~
For CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses2 y( o' {5 d( y+ {
the insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is. W# ~* f* y$ k+ ^5 l
permissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for
- ?3 u3 H" L0 H5 z+ M- a6 z5 z9 ]CLEARANCE.7 E$ ?- |. @9 e/ {& x
4 @% K+ h! B1 c6 a+ e% b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。
* b9 o' K; M( Y* ^6 Z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' h4 {5 `3 R0 M" ?8 W' Ca.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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