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

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DSH 394A 4 i. b' `8 b3 ^! w* ^

Touch current for equipment having multiple supplies supplying power simultaneously : ?6 w+ ^" w) u; B* n5 s

5.1.2, last paragraph / 5.1 6 g. L( L7 ~. ]5 ~/ s, w) Z

60950-1(ed.1) & 60950(ed.3) + \* }' y- s$ h' k

Standard(s):
IEC 60950 (1999) 3rd Ed.
IEC 60950-1 (2001) 1st ed.
Sub clause(s):
5.1.2, last paragraph
3 F/ N+ @3 j6 w0 c% T3 c5.1
Sheet n°: 394A
Subject:
( U7 `4 w" g3 ITOUCH CURRENT for equipment
having multiple supplies supplying
4 j) Z  o! ^% F7 `, \; Wpower simultaneously
! L0 O/ G+ F) z1 Y( B" iKey words:
2 J, o( d0 a2 s0 t- TOUCH CURRENT for equipment
8 c5 e  d3 x. A) m. I; _. M  {with multiple supplies
) e/ {6 D, {" ], V) a  UDecision taken at the 41st
3 K) ~7 l. |" V1 V' l$ fCTL meeting 2004. This
decision replaces n. 394
taken at the 39th CTL
meeting 2002
; k( M' }3 R  [5 ?9 s" Y) h2 NQuestion:
1. 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
+ e/ T+ @9 _2 G3 p2 ]7 s5 j( Ior 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
- j* `, U) ^  M8 ], ureliable connection to PROTECTIVE EARTH (e.g. be PLUGGABLE TYPE B or PERMANENTLY
) ~5 M0 z; s! D' ~8 {% Wconnected EUT?
Rationale:
+ C/ U. u  {+ `  a) p3 PPLUGGABLE EQUIPMENT TYPE A does not have a reliable connection to building PROTECTIVE EARTH. Therefore, if
the 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
" P+ [* c6 }3 {not be present on the PLUGGABLE TYPE A socket outlets on the wall. The multiple connection does not help, as all
  e, s3 Q# q0 M0 E( N" l; n4 ~0 nsuch socket outlets may not have EARTH connection. Therefore, if the individual or cumulative PROTECTIVE
2 W) l  \4 g% P- j. X8 ^. |" bCONDUCTOR CURRENT exceeds 3.5 mA, then at least one of the sources needs to be PERMANENTLY connected or
& @" o  q& k; F- i7 P8 mhave 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
% o, I$ k4 y. M/ q; n+ ]8 }comply with the TOUCH CURRENT requirements, the equipment shall be provided with both a marking on the equipment
and a statement in the installation instructions, specifying that the USER is to disconnect all power sources connection
; B0 `  \2 S1 Z# t9 Zbefore disconnecting the PERMANENT connection or the PLUGGABLE TYPE B connection
Decision:
% C8 S( P' Q, h. J) MSee copy of the CDV for IEC 60950-1 2nd edition on Page 2

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