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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: J9 j! P3 u, x& U, |$ S3 b& E- ~
9 f% N' P( x+ x6 l: h. l
Separation of TNV-3 and SELV circuitry
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2.3.2" \' e; }* u! q. H' O
60950(ed.3)
' J6 }% r$ ?( e7 c! p& ~) W0 u
( Y/ N% I; ~2 I; b+ [" E
Standard(s):  I# _( d5 _7 N+ H+ \
IEC 60950 (1999) 3rd Ed.
+ e, Y' m" l8 U, ?5 a9 h, `Sub clause(s):' I- v1 \6 @6 G+ E; U$ y
2.3.22 d9 ^* l  h  R* F3 r' Z6 W. v
Sheet No.5 ?- w& B7 }& F" H1 [3 M( i5 E
395
4 c# a. o4 R7 ~0 O8 [Subject:/ E" d- W& |4 c+ l, m( K
Separation of TNV –3 and SELV' k: G. B+ u7 e9 \
circuitry7 P) m) W8 V1 q- n. B3 ~+ g
Key words:2 N4 A, I: f: x8 P; t* Y
- Separation of TNV-3 circuit
. D2 u3 k, M/ Pand SELV circuit
% _+ ?  F3 D! b. f5 u/ ]# sDecision taken at the 39th, K0 v% c: [. D/ I  Q; G
meeting 2002
' Q  @; ~5 }5 e: m& a: I& MQuestion:: Y" F, [4 B3 z1 j& {$ L; p6 h
1. Is it permitted to demonstrate that a TNV -3 circuit is adequately separated from a SELV circuit by
8 y+ Z- }. |% F( D6 ^6 y/ @1 z. Imeans of single fault testing, in the situation where the spacings do not meet the requirements for basic
" N7 x# n& q  tinsulation? (The dielectric strength test is still required under Subclause 6.2.1.)
+ O1 t' d/ S; M6 M3 n2. If so, is it required under the compliance paragraph to short circuit the insulation between the TNVcircuit
- Q) J% J* D* B3 Sand the SELV circuit at all points which do not meet the criteria for basic insulation, before: m; ^" c) M6 g# d5 |
carrying out the tests?5 C1 D! Q4 r( ?: H+ N$ l, s% R
3. If short circuiting the insulation before carrying out fault tests results in the equipment passing the tests,0 B+ i& `4 s; W
whereas carrying out the fault tests without short circuiting the insulation would result in the equipment
0 \. ]+ V) J" \7 W0 W' H0 L7 K3 Yfailing the test, should the insulation be short circuited?
9 V( E" N8 g* B( s( r& A5 PRationale:) e1 m) ^2 W, i0 ~& [% C7 \" @
1. Paragraph 1 of Sub-clause 2.3.2 requires that separation between a TNV-3 and a SELV circuit be such
2 a! V2 i7 K+ `/ M6 d  Zthat in the event of a single fault, the SELV circuit remains below TNV-3 limits. Paragraph 2 of Subclause
9 I9 O8 z! v; z5 S2.3.2 states that basic insulation will achieve this, but other solutions are not excluded.
+ D/ b: F. m' a; I) cEquipment is not required to meet either Paragraph 2 or 3. It can meet the single fault conditions stated
  A: t, w7 k; T) x5 l$ Hin Paragraph one and in the compliance paragraph.0 D8 ^8 g+ w9 O; c+ z3 Y
2. According to the compliance paragraph, before carrying out the single fault tests, insulation which does9 U" U5 S' ?5 r& P7 M
not meet the requirements for basic insulation is short circuited. Presumably this does not mean that
. s: @3 W) {0 \$ W$ T% I! ^5 J2 Vshort circuits are to be applied between all tracks and components in the entire TNV-3 and SELV
. r/ t7 L) O3 ]circuitry which do not meet basic insulation, but that the insulation at the point where the TNV-3 circuit
$ a$ I/ O0 O! Dmeets the SELV circuit is short-circuited.
1 I1 [7 y% D# ?( }1 f3. It is possible to envisage a situation where short circuiting the insulation between TNV-3 and SELV7 Z! |$ \& s# ?% ]
could cause the TNV-3 voltages to be lowered. Fault tests under this condition would not represent the" X/ D) F- g9 o$ d6 y
worst case possible fault condition& ]; h- G. [* J+ G4 [7 o
Decision:4 ~- Z9 b  e% S) e8 G' m+ `& t
1. It is permitted to demonstrate compliance with Subclause 2.3.2 by means of single fault testing.2 [& X0 e2 `" l$ |! j+ P
The limits in 2.3.1.b) shall not be exceeded in normal or single fault conditions.
4 u6 q( I9 E" G9 D( t0 w4 z; A' Q2. Before carrying out single fault testing of components and insulation, insulation between TNV-3 and; s. Y% h2 {! A- H
SELV circuits not meeting the requirements of Basic insulation should be short circuited if this results in4 j  I$ K+ \3 K9 V2 c
a worst case voltage measurement at accessible parts of SELV and TNV-1 circuits, and at accessible
2 F3 N& L" A* E6 I# ]' T+ T, [conductive parts during subsequent fault testing.
+ r" G& G* `, u8 W* C3. If the single fault test would be more severe if carried out without short circuiting the insulation, the test
7 n8 [' @+ V- ~% n# Rshould be done without short circuiting the insulation.
' }. T7 T0 y% R# F  z4 |: I* |" N" F: ?

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