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标题: DSH 394A Touch current for equipment having multiple supplies supplying power [打印本页]
作者: 小米    时间: 2012-11-6 17:06
标题: DSH 394A Touch current for equipment having multiple supplies supplying power
DSH 394A
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5 g5 U+ B: @! ^/ ~		Touch current for equipment having multiple supplies supplying power simultaneously
2 |' ]# W! d: h		5.1.2, last paragraph / 5.14 C7 U3 Q1 s, d/ x: @/ W. ^% Y+ G
60950-1(ed.1) & 60950(ed.3)1 {) v) d2 T1 l; r6 N0 c

8 l( _% m; R) R) {2 d( z* mStandard(s):
" `0 V: F6 B+ m& `) f2 X" BIEC 60950 (1999) 3rd Ed.
" Y0 r5 F. C7 }( c& T, aIEC 60950-1 (2001) 1st ed.. ?/ O2 p. \; x$ H
Sub clause(s):/ q& y: p+ T- J. b
5.1.2, last paragraph; w* U$ S  p: q7 ?# `9 T
5.1+ _3 m/ |# }3 U  H/ }  T& ~+ R9 Z
Sheet n°: 394A! q) \6 T+ m& j! U1 A
Subject:1 r+ S  T% Y  W8 I+ E/ E7 t
TOUCH CURRENT for equipment
5 J1 U7 h5 v! i" Chaving multiple supplies supplying
: a9 U+ ~. i  P$ m6 u$ kpower simultaneously
$ Z' v& x  H# @( T9 P% @Key words:
8 q, M2 ~0 I6 ]0 ?$ R1 {4 u) ]  F- TOUCH CURRENT for equipment
$ I0 ]. g1 ?" d1 Rwith multiple supplies
& ^  a8 N, H) aDecision taken at the 41st
: \( D+ L- |  y* DCTL meeting 2004. This
2 W  r9 A' X5 `" z! |3 \; m3 \! xdecision replaces n. 394  p$ r5 ~1 S* L* |. F
taken at the 39th CTL" r, L! t: b) Y: E$ t5 w5 O# G" Y6 O
meeting 2002
$ }& d* f$ ?$ S6 OQuestion:2 ^( B% g( z  V* u  k. r) B
1. Should the TOUCH CURRENT be measured for each individual supply source to determine if the( ]# B% t: w( S2 _% O( B: p
PROTECTIVE CONDUCTOR CURRENT exceeds 3.5 mA and if it does exceed, then require PERMANENT
, o$ a9 D! T3 F* d8 _) o+ Aor PLUGGABLE TYPE B connection to the supply and meet 5.1.7?: N+ `  k* |8 i5 r0 `
2. Should the cumulative TOUCH CURRENT be measured to determine if the total TOUCH CURRENT
- Z( m  c, f( E, `exceeds 3.5 mA? If the total TOUCH CURRENT does exceed 3.5 mA then require that AC MAINS2 R, F& |$ Q& a( K
SUPPLY to be connected to separate AC MAINS SUPPLY circuits with at least one source having a
9 @3 Y8 \! B  t3 g: b& ^reliable connection to PROTECTIVE EARTH (e.g. be PLUGGABLE TYPE B or PERMANENTLY2 ^7 R, J7 w# b* Z5 Z( Q
connected EUT?
  l9 ^/ B; Z" @  F5 WRationale:9 _* o% _# Q0 M& W$ t- U3 h0 k
PLUGGABLE EQUIPMENT TYPE A does not have a reliable connection to building PROTECTIVE EARTH. Therefore, if7 }  A2 e/ `$ q' I5 C' P  y# {
the TOUCH CURRENT measurement exceeds 3.5 mA, then that particular source needs to be PERMANENTLY
3 w( P. K2 M- G; s( l) {1 uconnected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. In older buildings, EARTH may
3 g! y6 F: o* l, Bnot be present on the PLUGGABLE TYPE A socket outlets on the wall. The multiple connection does not help, as all
! d( ]& j1 w7 [" Q' k; vsuch socket outlets may not have EARTH connection. Therefore, if the individual or cumulative PROTECTIVE
" A- i% k! F; s/ ^" I' ~CONDUCTOR CURRENT exceeds 3.5 mA, then at least one of the sources needs to be PERMANENTLY connected or
8 E6 Z8 m- }- `+ x. }have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. If one of the sources is required to be
' H* F9 r1 i: p+ l+ W$ k8 A/ n) uPERMANENTLY connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH in order to
! ^7 C4 w4 Z3 h) G( Tcomply with the TOUCH CURRENT requirements, the equipment shall be provided with both a marking on the equipment. x; K/ T3 l) X3 C8 |  h- ~8 q* U
and a statement in the installation instructions, specifying that the USER is to disconnect all power sources connection
7 W( ~0 y7 m6 G2 H, M9 S7 \3 Fbefore disconnecting the PERMANENT connection or the PLUGGABLE TYPE B connection$ O6 x0 T3 i- O8 N9 k% ~
Decision:
% m- a: K) d& ^- ~; D3 |! w# ^; CSee copy of the CDV for IEC 60950-1 2nd edition on Page 26 [; p  W9 u( S7 w3 F" q7 x) z1 s. N
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