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楼主 |
发表于 2014-5-17 10:32
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没有说要在故障情况下（open R1）.
2 M( z& Z+ U# r2 \+ d1 o2.1.1.7 Discharge of capacitors in equipment# y; d6 w" s: n2 [' [6 p. q5 ~ t
Equipment shall be so designed that, at an OPERATOR-accessible external point of
. H. C" ~5 |5 W Z4 ]$ i3 l: ddisconnection of a MAINS SUPPLY, the risk of electric shock from stored charge on capacitors
& x4 o7 O1 f' `* z \connected in the equipment is reduced. No test for shock hazard is required unless the
1 w) _% T6 k2 U, ^. R. o% Gnominal voltage of the MAINS SUPPLY exceeds 42,4V peak or 60V d.c. 3 l5 y* E7 c: e* V' F% f
Compliance is checked by inspection of the equipment and relevant circuit diagrams, taking
" Y( G n* B6 ^4 W. _4 Z* B3 H# |into account the possibility of disconnection of the supply with any on/off switch in either 1 I9 |5 i& f$ S7 M
position.
; W% x4 N' Q, uEquipment is considered to comply if any capacitor having a marked or nominal capacitance
2 |7 x$ Y( N4 Iexceeding 0,1 µF and in a circuit connected to the MAINS SUPPLY has a means of discharge
5 ?' C' q# i$ v5 }resulting in a time constant not exceeding:
/ y6 i! D$ \5 O1 W− 1 s for PLUGGABLE EQUIPMENT TYPE A; and
/ p" f4 d7 _7 Q; M/ z% p! w: j− 10 s for PLUGGABLE EQUIPMENT TYPE B. " l G% L8 t% ~( U' o( r2 c2 y, @$ O: h
The relevant time constant is the product of the effective capacitance in microfarads and the
9 _& [* d) j; d: \8 Heffective discharge resistance in megohms. If it is difficult to determine the effective 8 |) W X p4 P# ^ P* K
capacitance and resistance values, a measurement of voltage decay at the point of external % {! I$ R- g* B# o" p: W
disconnection can be used. When conducting the voltage decay measurement, the result is
' s- Z! a' c+ B/ ? C0 S5 ?2 jthe measurement is either made with, or referred to, an instrument having an input impedance
9 e* v8 Z4 O) l7 K4 I$ P* P7 s# ?consisting of a resistance of 100MΩ ±5 MΩ in parallel with an input capacitance of . l+ {8 r, u5 d
20 pF ±5 pF 25 pF or less. |
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