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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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Touch current for equipment having multiple supplies supplying power simultaneously
  d+ k4 x- \( G7 P		5.1.2, last paragraph / 5.14 ]6 `/ x- r4 j: h
60950-1(ed.1) & 60950(ed.3)
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* K) ]. v  n- |2 h& N7 xStandard(s):
+ ^  I4 U* ~' M% X. ^# U$ P1 KIEC 60950 (1999) 3rd Ed.
) l+ }! s  x/ V+ EIEC 60950-1 (2001) 1st ed.
& Z0 d3 Y3 V+ Y: HSub clause(s):4 M# `# u1 l8 n, F! B( a
5.1.2, last paragraph
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$ [. y! ^4 @9 j7 [* g4 hSheet n°: 394A% n; T* m1 D$ m. A& k
Subject:3 i; Q4 D2 C  q6 r- t
TOUCH CURRENT for equipment
9 v+ V. G& E+ l  i9 t5 Rhaving multiple supplies supplying
1 o0 S$ D7 C6 tpower simultaneously
% ^% F( [( Z  Z" t" XKey words:" h* @6 ]6 T0 p. z" u4 I# |- S
- TOUCH CURRENT for equipment
  N" z# ~6 A; }2 S, {with multiple supplies
, c$ c: x7 i: J3 _2 L  pDecision taken at the 41st4 K2 e; ]$ n+ A' `/ ]5 e9 Q) d
CTL meeting 2004. This& F% I  `. y  j5 ~! r7 A+ H
decision replaces n. 394
; }# I: u2 _7 ^: M7 F' Ataken at the 39th CTL5 h) W0 ^( T9 _# t1 d  X5 P5 i( J! C
meeting 2002
! @2 y+ S* c- y" ]Question:
+ j* v  d+ v4 X! N! i1. Should the TOUCH CURRENT be measured for each individual supply source to determine if the2 S6 k0 ^  \9 m% r
PROTECTIVE CONDUCTOR CURRENT exceeds 3.5 mA and if it does exceed, then require PERMANENT8 U3 D% J3 ]* a( c5 Q9 @( ^
or PLUGGABLE TYPE B connection to the supply and meet 5.1.7?
1 z' Y: ^# n) h4 ^3 d  Z5 p2. Should the cumulative TOUCH CURRENT be measured to determine if the total TOUCH CURRENT
7 T1 ?4 F  [- Z2 u0 J; s  G7 mexceeds 3.5 mA? If the total TOUCH CURRENT does exceed 3.5 mA then require that AC MAINS
5 L2 q  s& l  g& K' H1 oSUPPLY to be connected to separate AC MAINS SUPPLY circuits with at least one source having a1 Z0 s# ?0 T% |" r; W
reliable connection to PROTECTIVE EARTH (e.g. be PLUGGABLE TYPE B or PERMANENTLY
& A, S. }1 O0 cconnected EUT?6 `& a5 v7 V0 s' F5 ^
Rationale:
1 J$ A/ ?  i( X$ L( b3 rPLUGGABLE EQUIPMENT TYPE A does not have a reliable connection to building PROTECTIVE EARTH. Therefore, if
6 D- ]# C+ a& `+ q$ W) `, x+ Pthe TOUCH CURRENT measurement exceeds 3.5 mA, then that particular source needs to be PERMANENTLY' ]$ r9 L& L2 U8 W  p# A: J* F
connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. In older buildings, EARTH may
8 }$ \+ K$ m8 Cnot be present on the PLUGGABLE TYPE A socket outlets on the wall. The multiple connection does not help, as all5 i! _. x9 ^# t$ u3 B
such socket outlets may not have EARTH connection. Therefore, if the individual or cumulative PROTECTIVE
8 S4 w: I/ N# n9 c0 [: NCONDUCTOR CURRENT exceeds 3.5 mA, then at least one of the sources needs to be PERMANENTLY connected or, j+ S$ K# O; u
have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. If one of the sources is required to be0 n8 e2 U5 g& m$ A( G$ G7 m3 R
PERMANENTLY connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH in order to
( K6 }' p0 H. F4 X3 B3 wcomply with the TOUCH CURRENT requirements, the equipment shall be provided with both a marking on the equipment
( X2 W$ [1 V5 Z. w: ?and a statement in the installation instructions, specifying that the USER is to disconnect all power sources connection& z0 {$ g- T+ I% F" R
before disconnecting the PERMANENT connection or the PLUGGABLE TYPE B connection% ~, X1 m3 z  s6 S
Decision:
! r' l- @: {& [' U. mSee copy of the CDV for IEC 60950-1 2nd edition on Page 25 p! g. z2 v) r% I& m: e

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