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[OFF] DSH 395 Separation of TNV-3 and SELV circuitry

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发表于 2012-11-6 17:01 | 显示全部楼层 |阅读模式
广东安规检测
有限公司提供:
DSH 395$ a# K+ m/ ~8 h8 D. \
* x1 I4 t% Z, v8 _. \9 r0 t
Separation of TNV-3 and SELV circuitry
* u5 F1 }$ }# R' v; A8 E, t
2.3.2
. l) D! Z2 e# D
60950(ed.3)' L6 f6 ~* ^/ u! G" q+ H+ [
8 Y; x. s2 P: i% p- ^- i* [: f5 z+ r
Standard(s):
9 s+ N8 p) E: `  K' PIEC 60950 (1999) 3rd Ed." g0 F8 g4 k/ Y7 q% s& m
Sub clause(s):& M: Y, I! }, P; S; m2 a2 ~
2.3.2
$ I+ T- X7 q* m) j3 s7 }! ]Sheet No./ J! ~2 g' O5 g, W  x3 Z
3953 b3 _# q3 B! P! n
Subject:
. ]& F- z3 L; ?; [  v3 pSeparation of TNV –3 and SELV) _4 r  j- D5 h% d% }- [
circuitry
- O5 A4 h+ _1 V  d5 G- cKey words:
/ f+ y2 E: M& W2 H8 T2 T- Separation of TNV-3 circuit! Z* p. G0 B' k; C* f, M- Y
and SELV circuit. q5 u+ [# `% T! ]& U1 ^' |
Decision taken at the 39th0 x; A0 I8 }9 d
meeting 2002
" Y' d& h* F$ ^0 F4 GQuestion:
# V/ P! X7 X! [. C1 K  ]1. Is it permitted to demonstrate that a TNV -3 circuit is adequately separated from a SELV circuit by
8 ~& j5 p9 x% c- Nmeans of single fault testing, in the situation where the spacings do not meet the requirements for basic
# W( }* {. S4 v3 o1 i) m5 l; u- cinsulation? (The dielectric strength test is still required under Subclause 6.2.1.)( z$ P& u; n$ H9 @# p1 X9 [
2. If so, is it required under the compliance paragraph to short circuit the insulation between the TNVcircuit
' M& o: T/ e* }+ |: A2 vand the SELV circuit at all points which do not meet the criteria for basic insulation, before9 a+ c4 o% v! C
carrying out the tests?( @+ `  q- O+ U8 [+ L( R* y8 q7 _
3. If short circuiting the insulation before carrying out fault tests results in the equipment passing the tests,
+ |$ M. e& m8 x) owhereas carrying out the fault tests without short circuiting the insulation would result in the equipment9 L* {  Y  P2 J* y; u/ O8 U3 U5 W
failing the test, should the insulation be short circuited?
7 ?' U  c+ o& W* O7 _9 T+ t' GRationale:; E) }2 ~6 t  }/ ^0 l
1. Paragraph 1 of Sub-clause 2.3.2 requires that separation between a TNV-3 and a SELV circuit be such/ x" K( L  E% b! I! E7 Z
that in the event of a single fault, the SELV circuit remains below TNV-3 limits. Paragraph 2 of Subclause
, A, T- k3 F8 o; Q& g; \1 ]- W) t2.3.2 states that basic insulation will achieve this, but other solutions are not excluded.
# K/ D$ u6 C5 n" S& s. j/ R$ dEquipment is not required to meet either Paragraph 2 or 3. It can meet the single fault conditions stated1 U& Y2 g$ ~- P' D! ]
in Paragraph one and in the compliance paragraph.
% R) m4 J6 ]: ?$ C! S2. According to the compliance paragraph, before carrying out the single fault tests, insulation which does
9 ]# ]) D7 G4 d1 k# Q1 m1 anot meet the requirements for basic insulation is short circuited. Presumably this does not mean that
, C2 L1 k$ r( N" ~1 Jshort circuits are to be applied between all tracks and components in the entire TNV-3 and SELV' T) P: n6 J$ I0 V5 p
circuitry which do not meet basic insulation, but that the insulation at the point where the TNV-3 circuit
% E- t* o- W' ^% X9 \1 Ymeets the SELV circuit is short-circuited.
# j7 Q7 N) v0 R: G9 V4 p5 y3. It is possible to envisage a situation where short circuiting the insulation between TNV-3 and SELV
4 N* `2 F  q& l; _% P5 ^3 Icould cause the TNV-3 voltages to be lowered. Fault tests under this condition would not represent the/ b9 K: x/ Q- C/ U6 E
worst case possible fault condition
% L( t9 e+ z# j4 uDecision:
: Q$ N6 Z$ c, U1. It is permitted to demonstrate compliance with Subclause 2.3.2 by means of single fault testing.( B+ J9 h6 P9 E& J
The limits in 2.3.1.b) shall not be exceeded in normal or single fault conditions.
+ O; K0 y" F! e8 w0 S+ ~2. Before carrying out single fault testing of components and insulation, insulation between TNV-3 and
# r4 l' V+ \6 H: O4 jSELV circuits not meeting the requirements of Basic insulation should be short circuited if this results in3 e2 T/ X' \. Z/ M% K: }
a worst case voltage measurement at accessible parts of SELV and TNV-1 circuits, and at accessible- M6 _' U3 E& H3 Z
conductive parts during subsequent fault testing.. S3 `& q7 A6 p5 q; u; s
3. If the single fault test would be more severe if carried out without short circuiting the insulation, the test% \  H; D% ?, D3 [3 Q
should be done without short circuiting the insulation.
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+ m+ O9 L0 F4 s" J6 t3 R

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