|
|
附件是CTL decision sheet 416，大家讨论。
* o1 u8 _' \& @1 w( d( hQuestion:
6 p0 g+ t- r$ y$ [$ N9 Y. b# l1 u4 VEQUIPMENT may contain floating circuits which under the definition 2.1.10 would not be) Y2 E. z( U; J. e8 r$ j# k
considered as LIVE, since contact with these parts could not result in excessive leakage
8 K; [( p/ H3 X9 \2 g1 V! r1 Qcurrents to earth or to other ACCESSIBLE PARTS. There would therefore appear to be no
6 `8 U) I' V& r3 H0 Z6 j( @requirements for safety separation between these circuits and ACCESSIBLE PARTS or% [* b& C, |- [2 g
APPLIED PARTS. But voltages within these circuits or in conjunction with other circuits may- }4 Q, E" g" @
lead to currents exceeding the values given in Table IV.# V: s1 G- t1 P1 K0 t
Decision:! ]( ?- R8 _# }
If the failure of insulation of such isolated circuits is likely to lead to a SAFETY HAZARD, such
7 E* [8 F2 X; P I2 d* Ainsulation should be short-circuited before determining whether a part is LIVE. This shortcircuit1 }. u/ M; N* o6 @ p7 F$ h r& ~$ D
should not be treated as a SINGLE FAULT CONDIT ION unless the insulation
& N2 Z# T# C7 H8 O3 hconcerned satisfies the requirements for BASIC or SUPPLEMENTARY INSULATION/ ?2 U% C* p4 Q" H
necessary for the voltages within the isolated part.
3 c5 d, J6 m+ Z8 i/ J4 O, WExplanatory notes:$ ^6 q% N) R2 g9 q9 d* n. `0 k
There are two possibilities for solving this problem. One is to change the definition of LIVE and: S/ w9 ?% n% I
adopt the requirements for insulation accordingly. The second is to treat the separation of the
! [2 @6 ?/ H: F! Nisolated circuits as subject to failure.
1 e2 `' Q% }+ G/ KIf one pole of the isolated circuit is short-circuited to earth (failure of insulation) then the other
* y* L) k+ L/ @# qpole becomes LIVE and the adequacy of the separation of this LIVE part under these
( W$ e# x# V$ R/ M0 t! Q; oconditions may be assessed. If that separation is inadequate then it should be short-circuited
2 f& j- Y. i* j8 F# ]& Ein turn to assess the separation on the other pole.0 Z! D Q6 t, G$ T$ e
Since for an isolated circuit there may be two separate protective insulations (on either pole),& s/ A$ e9 ], P7 w5 r1 U. L
each of these can be BASIC INSULATION rather than BASIC and SUPPLEMENTARY
4 {' L" \& G5 J! CINSULATION. Of course other combinations may be used although if the insulation of one
1 J F! n# m# f" zpole is less than BASIC INSULATION then the other pole must have DOUBLE or
0 B/ `. Y$ N% [! L; |5 uREINFORCED INSULATION. |
本帖子中包含更多资源
您需要 登录 才可以下载或查看，没有账号？注册安规
x
|
|关于安规|小黑屋|安规QQ群|Archiver|手机版|安规网
( 粤ICP13023453-10 )
窥视卡
雷达卡
发表于 2008-10-16 09:34
显身卡
楼主
发表于 2008-10-21 05:05