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高人指导下，同学习
: s4 g/ y) f/ c2 ^2 X2.10.4.2 Material group and comparative tracking index" p. y( t7 |+ s+ o
Material groups depend on the comparative tracking index (CTI) and are classified as follows:5 K8 \/ I; p, x. _: X& i: c
Material Group I CTI ³ 600. W# q. T: [ G, p- X
Material Group II 400 £ CTI < 600" M0 M- c6 O6 f# l8 a: B( i
Material Group IIIa 175 £ CTI < 400
' q; S8 D: b. Z1 \0 e+ }Material Group IIIb 100 £ CTI < 175( ~; d0 O* s: \: [* M+ j
The material group is verified by evaluation of the test data for the material according to IEC# k/ q: o% {- s* v
60112 using 50 drops of solution A.
0 O* `8 E) [( {! IIf the material group is not known, Material Group IIIb shall be assumed.
* D$ \8 y( M) \/ QIf a CTI of 175 or greater is needed, and the data is not available, the material group can be
P6 `, W4 _8 `* Zestablished with a test for proof tracking index (PTI) as detailed in IEC 60112. A material may
2 O" h; [; A+ X# z8 ^be included in a group if its PTI established by these tests is equal to, or greater than, the lower" ?5 d" H* T7 q9 W9 J, U1 r
value of the CTI specified for the group.
. e' A; b. ^& c$ c
% \; s, D6 T) ?- ]0 @——UL60950-1-2007 |
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