DSH 717 Creepage and clearance determination, groove, recess, corner, bridging o

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DSH 717

Creepage and clearance determination, groove, recess, corner, bridging of distance X

4.2, 6.2 6 a" h2 k* a! [8 h, i3 Q+ @

60664-1(ed.1.2) & 60065-1(ed.2) & All equipment standards based on these ' M& K1 C% R4 B# \9 K$ J

Standard(s): No. Year
! @. T8 g/ Z/ u8 ?" K, YIEC 60664-1/2002 ed1.2
; T$ h# [8 Z3 y; E3 |8 y( H0 @( aIEC 60664-1/2007 ed2.0
3 R) ^5 W$ |+ I! _8 z8 R3 AAll equipment standards
based on these
DSH
6 L! {6 ?/ `7 E3 H9 D  h) W0717
2008
Categories:
Various, General
Subclause(s):
4.2
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Developed by:
WG2 - WG4
Subject:
7 t+ c) T: d2 QCreepage and clearance
* I* @8 E( F5 \; xdetermination, groove,
recess, corner, bridging
( ^7 A- w* K5 ^& {  Tof distance X
' U; t' @. J7 q3 @" k# BKey words:
- Creepage
1 q8 i7 ?5 e6 o5 I: ]0 s- Clearance
! G# l6 z# G( H- Groove
- Recess
- Corner
- Bridging of distance
$ B# l( U0 b2 OX
- k9 q( Q& E" X8 C( tDecision approved at the
2009 CTL Plenary
9 @) z, g$ c1 f' [5 tMeeting
/ p/ r5 h6 D* K. @Questions:
1) How shall the examples given in IEC 60664 be interpreted for intermediate situations?
: S0 Z& V2 l) \2 ]+ \' N( a2) How shall the example given below be judged correctly, based on the examples given in
IEC 60664-1 and based on the assumption that X = 1 mm?
; _1 D3 J$ `: r0,8mm
2 mm
PCB
9 I3 C# u, \; w; x2 N6 Q6 p8 NPCB-Track (ending on the
/ }/ m7 I* u( N: e; {2 Tedge of the cut-out
+ D( g' x( P& q) h3) When shall the sentence:
% l- m- M0 m. u“If the associated clearance is less than 3 mm, the minimum dimension X may be reduced to
one third of this clearance.” be applied?
Does this sentence refer to the actual clearance measured or to the minimum clearance
required?
Decisions:
% [, }2 p+ B# U3 hAd 1)
An intermediate situation not covered directly by the Standard shall be determined by
considering it as an extension of the most appropriate example from the Standard. An example
7 o: t+ Y- }3 J! `9 k7 pof the methodology is given in the Explanatory Notes to Question 2."
Ad 2)
3 Z4 f1 w+ @: _# J1 ?, [* E% lThe example shall be judged without any bridging of the corner in the cut-out

creepage = 2,8 mm, no shortcut applicable.
Ad 3)
The sentence shall always be applied whenever the required clearance is less than
/ N2 Z3 T# K/ W& V! d4 u3 mm and the allowed reduction of the minimum dimension X shall be referred to 1/3 of the
required minimum clearance.
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