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
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Standard(s):" S1 X0 O0 ?+ x" ]6 E9 R
IEC 60950 (1999) 3rd Ed.; D, R: P2 ~3 G/ Z' w4 f, N
IEC 60950-1 (2001) 1st ed. 0 l! p' k0 X2 K3 JSub clause(s): 4 {& R4 {3 U8 p# |5.1.2, last paragraph. ]; z* F/ d% y1 {) ^* Q3 A
5.1 + S2 J) k0 o. K& mSheet n°: 394A 4 ^. r/ D7 j: _: w: m) y5 ]2 oSubject: 4 y7 a+ m9 b9 X. F# G- oTOUCH CURRENT for equipment 1 G$ b8 e% `$ z p0 H- Bhaving multiple supplies supplying " E1 N9 u, k# h( u2 t) `power simultaneously / y" n) x4 A: I7 z9 ~Key words:/ K2 _; J* ^8 @$ A0 L9 u$ r3 x" x
- TOUCH CURRENT for equipment' _1 I. n1 }8 a2 A& h$ s U
with multiple supplies * o% `- u4 ^3 j6 wDecision taken at the 41st# {* c5 e. `( b0 f& _! A
CTL meeting 2004. This , {, m+ N9 }, |1 H( f6 S; q3 X& \decision replaces n. 394 : x! A. e% f6 H0 b0 h5 |7 Otaken at the 39th CTL 6 F: m. j4 d2 n: J0 S- Wmeeting 2002 0 E5 t+ A# T, U0 J5 DQuestion: / g& ]7 ]6 i* H8 t' ?. e' Q1. Should the TOUCH CURRENT be measured for each individual supply source to determine if the + D7 {: B- Q: gPROTECTIVE CONDUCTOR CURRENT exceeds 3.5 mA and if it does exceed, then require PERMANENT % {; h& o: f1 Mor PLUGGABLE TYPE B connection to the supply and meet 5.1.7? 4 V- j4 a- \7 u& @2. Should the cumulative TOUCH CURRENT be measured to determine if the total TOUCH CURRENT" e1 ?8 u* }4 g3 A c0 V
exceeds 3.5 mA? If the total TOUCH CURRENT does exceed 3.5 mA then require that AC MAINS" k* C1 z1 t& A) m; d
SUPPLY to be connected to separate AC MAINS SUPPLY circuits with at least one source having a 3 P; ]+ t. `6 Jreliable connection to PROTECTIVE EARTH (e.g. be PLUGGABLE TYPE B or PERMANENTLY! s3 ^# U8 y% a- m% k8 K
connected EUT? ) D: w' c* z- N2 xRationale:- B8 n+ z$ u) Y; r: J
PLUGGABLE EQUIPMENT TYPE A does not have a reliable connection to building PROTECTIVE EARTH. Therefore, if$ [# M1 ]& } r- l
the TOUCH CURRENT measurement exceeds 3.5 mA, then that particular source needs to be PERMANENTLY : N5 X/ \0 O9 {# ^& B( c! Y: Lconnected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. In older buildings, EARTH may+ B4 I- `3 S3 d# {( T2 k! G8 s
not be present on the PLUGGABLE TYPE A socket outlets on the wall. The multiple connection does not help, as all( @3 U1 w" {* l0 c; ~8 w
such socket outlets may not have EARTH connection. Therefore, if the individual or cumulative PROTECTIVE$ h. \$ ]% \& g) O
CONDUCTOR CURRENT exceeds 3.5 mA, then at least one of the sources needs to be PERMANENTLY connected or6 k5 T- C2 A' O( b
have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH. If one of the sources is required to be) D/ A; b2 A- C$ r2 h& G3 W! Z2 Z
PERMANENTLY connected or have a PLUGGABLE TYPE B connection to PROTECTIVE EARTH in order to - k% j Q5 b; f4 F \9 w# hcomply with the TOUCH CURRENT requirements, the equipment shall be provided with both a marking on the equipment2 ?# v0 g3 U/ X
and a statement in the installation instructions, specifying that the USER is to disconnect all power sources connection3 z( J: {' e t9 b3 F: a: Z& C
before disconnecting the PERMANENT connection or the PLUGGABLE TYPE B connection$ X6 Q* {* I+ @
Decision:' ]2 w/ S' X$ {' F. O
See copy of the CDV for IEC 60950-1 2nd edition on Page 20 t- z- a' w: d7 W
- n0 I" f. \4 d$ S5 f" N2 k[attach]77167[/attach] 3 h8 l0 W; i$ v
DSH 394A