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|  DSH 3843 N8 X c1 y% a# {
: E( H+ Q# h D; P | Lithium Cell Protection) a) x+ b# X) V3 y9 T
| 4.3.219 {9 D; P3 v. S5 k& d
| 60950(ed.2)& Z+ b* J0 v- F9 z2 X3 I7 F3 I
|
9 `# s( c$ G, m' i! x! I: mStandard: IEC60950, 2nd Clause: 4.3.21 Sheet n. P3848 F: ^" l2 R' I- I
Page 1(1)
. O( b) z4 d# o! n4 X2 xSubject: Lithium Cell Protection Key words:
% b" F1 H" V9 H! w; l& m-Lithium Cell5 W: h, ^ ^9 n
-Clearances
# i! f+ _5 ?' a+ i! r' |0 Z- failure mode% D2 X; i$ o2 i3 H9 M& S( U
Provisional Decision taken by ETF2
. w1 T" {& m3 @$ L* K3 A# eand to be approved by CTL at its7 s! ]5 e- Q3 Q* F
38th meeting, in Toronto
1 z6 l7 T& E* c; X# oQuestion:
+ T* a' U+ j5 U# o7 a0 |; OClause 4.3.21 requires that two levels of protection are required to prevent forced or reversed charge% [; M/ ?- m0 H7 k7 n9 H6 y
or forced discharge if this would result in a hazard. Conventionally a combination of resistor, diode9 ^* k8 G+ D. ~' K# U) g
or ic has been considered suitable and is for the series current path. However, a new consideration& k$ E* O5 ?% \+ u: p
has been raised in respect of adjacent tracks, separated by no more than operational insulation, which,% A5 J9 i4 }+ M/ ?0 _8 h X
under s/c conditions will bypass the protective series components and provide charging current for4 v9 W( n% @$ O: P; W
either chargeable or non-rechargeable batteries. Does this mean that there is therefore a requirement
/ q2 L7 x. M N8 I- s* wfor Reinforced separation?
" k- P% H G1 x4 [' u9 i; W" qIf that is the case, then the controlling factor is the clearance of 0.8mm in Table 5 (circuits not subject
, C3 n5 m6 r& \6 Fto transient over voltage). This is based on the fact that creepage cannot be less than clearance and
& D; `/ T% _ N5 w; zcreepage can be calculated to be, for example at +5V, 0.4mm (based on rounding up 0.12mm to
1 \9 B7 l$ j8 H+ j6 r$ s3 ]# B2 _0.2mm for Basic and doubling for reinforced.: i$ m/ m4 }! v( B/ a& y6 x$ r
Decision:
+ [. E" T' }0 r' j6 \) t8 v* hOperational insulation is suitable taking into account 5.4.4 because there is no risk of electric shock.
8 R5 _% ^: F" `1 ?(see 1.2.9.1)" X5 {) V& }7 q2 `+ |; Z5 N8 ^
Care should be taken by determining clearance and creepage distances which column of the table has
3 p( z/ p B/ j- F( y+ [. I" Q5 E2 G3 }7 sto be used.(Transients have to be taken into account)
H7 Q* ]8 T% U0 y- u5 o4 B: Q& T- h7 d+ u, w: O; H3 a
! U& T+ U- a+ M8 H- v0 a |
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