DSH 394A Touch current for equipment having multiple supplies supplying power

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DSH 394A ) d+ p" }; E8 R+ T$ H! [8 V5 s 2 @. h- _, U" r6 F% I" b  p

Touch current for equipment having multiple supplies supplying power simultaneously 0 _2 ~* _3 x; {5 f7 e

5.1.2, last paragraph / 5.1

60950-1(ed.1) & 60950(ed.3) $ t5 d1 }6 y+ |/ D/ r

Standard(s):
IEC 60950 (1999) 3rd Ed.
IEC 60950-1 (2001) 1st ed.
Sub clause(s):
. A+ D; U* Q4 Y1 d1 L% U6 T7 G1 E* M5.1.2, last paragraph
0 i! F5 |, `7 h" C8 E9 f, i; F6 ?5.1
" M, [# r4 H) P+ P, QSheet n°: 394A
& V& G8 m5 a8 O2 L6 S9 GSubject:
. E  |: s) W5 x! rTOUCH CURRENT for equipment
$ z( n2 S1 p# x( l7 Uhaving multiple supplies supplying
power simultaneously
% \. K- R8 v. f! T8 ]0 cKey words:
- TOUCH CURRENT for equipment
with multiple supplies
/ \* y# |, e: g. ^' i- c% pDecision taken at the 41st
9 D- f' T, t& y; o: Q+ F' FCTL meeting 2004. This
) ?8 E1 H- w, d7 T- _% V7 l" Pdecision replaces n. 394
taken at the 39th CTL
5 ?! U- v* a! \% S* [meeting 2002
Question:
. J. k. F. e, Z1. Should the TOUCH CURRENT be measured for each individual supply source to determine if the
PROTECTIVE CONDUCTOR CURRENT exceeds 3.5 mA and if it does exceed, then require PERMANENT
or PLUGGABLE TYPE B connection to the supply and meet 5.1.7?
2. Should the cumulative TOUCH CURRENT be measured to determine if the total TOUCH CURRENT
exceeds 3.5 mA? If the total TOUCH CURRENT does exceed 3.5 mA then require that AC MAINS
SUPPLY to be connected to separate AC MAINS SUPPLY circuits with at least one source having a
reliable connection to PROTECTIVE EARTH (e.g. be PLUGGABLE TYPE B or PERMANENTLY
, S" J" r" W  y, Zconnected EUT?
( i# t& z0 G6 g5 V  JRationale:
PLUGGABLE EQUIPMENT TYPE A does not have a reliable connection to building PROTECTIVE EARTH. Therefore, if
& V1 V0 |& b6 tthe TOUCH CURRENT measurement exceeds 3.5 mA, then that particular source needs to be PERMANENTLY
connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. In older buildings, EARTH may
" f9 G2 U  L$ G1 W7 B, tnot be present on the PLUGGABLE TYPE A socket outlets on the wall. The multiple connection does not help, as all
such socket outlets may not have EARTH connection. Therefore, if the individual or cumulative PROTECTIVE
) Q- Q" ?0 S( }0 zCONDUCTOR CURRENT exceeds 3.5 mA, then at least one of the sources needs to be PERMANENTLY connected or
have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. If one of the sources is required to be
PERMANENTLY connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH in order to
! {, }' d: C2 L2 t! x+ j3 ^3 [comply with the TOUCH CURRENT requirements, the equipment shall be provided with both a marking on the equipment
5 ~  @& [2 b, b9 jand a statement in the installation instructions, specifying that the USER is to disconnect all power sources connection
before disconnecting the PERMANENT connection or the PLUGGABLE TYPE B connection
9 Y2 l7 `- v! l2 B8 c& N6 L. aDecision:
6 ]& v8 K, k8 K9 d- @' [9 [See copy of the CDV for IEC 60950-1 2nd edition on Page 2
# s3 X) j+ O1 o6 i$ R

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