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引用第1楼yanfenghmm于2010-01-06 09:17发表的 : ~5 J: m# \' B2 V, s5 F% w
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
; ], i! c( U; x- V% ]+ E下面是table 4:, g e, v, d3 `0 H3 e, I/ Q Y
.: T s, f0 @7 W. w l
0 |8 i; v% S0 N ?/ P6.7.1.1 CLEARANCES
( ]1 J' z0 _- O* y! SCLEARANCES are specified to withstand the maximum transient overvoltage that can be
. G2 R8 x6 z' C qpresent on the circuit, either as a result of an external event (such as a lightning strike, or a
! Q- D8 {* y1 I8 E, V- Uswitching transient), or as the result of the operation of the equipment. If transient1 T2 t3 K6 d* g
overvoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.0 l2 A" B& |) _0 {' N# V, t
The value for CLEARANCE depends on3 k- F+ k' e. h7 B# U
a) the type of insulation (basic insulation, reinforced insulation, etc.);
8 J6 x9 j5 C1 i! _- U6 @( d' _b) the POLLUTION degree of the micro-environment of the CLEARANCE.& y x6 S! m) c5 E% s1 u, r8 K' m( h- }+ {* b
/ k* @& ^7 v) |6.7.1.2 CREEPAGE DISTANCES
$ y% Y& V$ L4 K4 u* c% TFor CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses
! ?4 a2 w# z. a( Fthe insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is
+ }4 C$ @$ T* d8 F: u3 U8 n/ Gpermissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for+ R! ~( o2 \: ^, U7 W
CLEARANCE. q; ^/ Q7 G& n% t d) q
2 ^ d0 b. u) |9 A% k, K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。6 f' t$ H& H; a O
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
( H7 Z$ ]/ E7 i* b9 ^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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