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Standard: IEC60950, 2nd Clause: 4.3.21 Sheet n. P384 ( S) r6 L8 N8 e. \Page 1(1) / u8 b U! c' ]Subject: Lithium Cell Protection Key words:9 e/ l: g! l- [9 d& i; e
-Lithium Cell- S9 S3 i) W/ [8 ~ ~
-Clearances& i! r8 R+ H! B: b/ _, {
- failure mode o, S, b9 c bProvisional Decision taken by ETF23 J. n0 J) a% M2 N- Y, g! f
and to be approved by CTL at its |1 i0 d7 M& O- j! b38th meeting, in Toronto p5 x A" ~7 a4 Z6 [6 E8 A
Question: 5 E! Q! c9 p; ^# yClause 4.3.21 requires that two levels of protection are required to prevent forced or reversed charge 2 z: |6 Q. P% a/ f7 d2 Nor forced discharge if this would result in a hazard. Conventionally a combination of resistor, diode " S: ~. j6 A7 [) H7 u8 f) aor ic has been considered suitable and is for the series current path. However, a new consideration 4 f6 o7 J6 t: _% ]& z( B+ R8 b1 Ahas been raised in respect of adjacent tracks, separated by no more than operational insulation, which, - p& T- ]' n) t0 z- K% wunder s/c conditions will bypass the protective series components and provide charging current for % y5 B* c- h( aeither chargeable or non-rechargeable batteries. Does this mean that there is therefore a requirement6 S7 y, E# M/ x% l! j
for Reinforced separation? 1 z& D9 T/ E7 j2 H5 PIf that is the case, then the controlling factor is the clearance of 0.8mm in Table 5 (circuits not subject 1 v. O" D5 h( lto transient over voltage). This is based on the fact that creepage cannot be less than clearance and * j$ V3 U' m! t6 z: Ycreepage can be calculated to be, for example at +5V, 0.4mm (based on rounding up 0.12mm to" ]' z+ R8 P" j# {) S2 ?5 }
0.2mm for Basic and doubling for reinforced. * j+ `! F* l4 z4 V4 q" h/ eDecision:( A: |5 _1 g. O( g5 y# n. \2 g
Operational insulation is suitable taking into account 5.4.4 because there is no risk of electric shock.( } Y8 h. w% B J
(see 1.2.9.1)$ K0 E$ \" e( y4 ?# K% J
Care should be taken by determining clearance and creepage distances which column of the table has p0 \' o6 U, s; d6 B0 b( E- l
to be used.(Transients have to be taken into account)* _1 R' E+ l# r, O% w! D
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