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引用第1楼yanfenghmm于2010-01-06 09:17发表的 : |* J; h1 e |: m {
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 l1 g+ H* F' Q. V下面是table 4:. S+ G3 f# W7 s) `5 D: F; X
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1 E, W. f/ {, S. g6.7.1.1 CLEARANCES
0 u/ s2 y: U1 M7 S: J5 `, `CLEARANCES are specified to withstand the maximum transient overvoltage that can be
) U4 m3 Y6 u9 Q/ J$ ]present on the circuit, either as a result of an external event (such as a lightning strike, or a9 u$ ~8 ?: E, H% }# I
switching transient), or as the result of the operation of the equipment. If transient
7 d$ [. y% \+ D$ K' Z7 L% }6 V n$ [overvoltages cannot occur, CLEARANCES are based on the maximum WORKING VOLTAGE.
0 g9 m; s7 O9 K0 t; f. a1 {) IThe value for CLEARANCE depends on1 S: x( ?% q2 G3 w& `& G g" B
a) the type of insulation (basic insulation, reinforced insulation, etc.);
) L N5 H3 Y+ W- E6 u5 b; } fb) the POLLUTION degree of the micro-environment of the CLEARANCE.$ E+ z1 E7 a! Y- u; K( v! V7 m( t" i
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6.7.1.2 CREEPAGE DISTANCES
7 \. S. k9 t0 X. y: T: WFor CREEPAGE DISTANCES between two circuits, the actual WORKING VOLTAGE which stresses
0 v/ r, K7 Y" c- S" L6 |the insulation between the circuits shall be used. Linear interpolation of CREEPAGE DISTANCE is
) i. ?. |8 V8 f' a rpermissible. CREEPAGE DISTANCE shall always be at least as large as the value specified for& Q; _0 Z- x) y! s- g% C4 `* M9 G" b
CLEARANCE.: E' E" {2 W' T
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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。
) e) b1 v: q" x) g& X: c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. ^+ J1 i5 L3 ?1 b* K& T: W' {
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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