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高人指导下，同学习# U! K' Y6 \9 U
2.10.4.2 Material group and comparative tracking index& r7 e2 {0 i& q$ M. y4 M
Material groups depend on the comparative tracking index (CTI) and are classified as follows:
+ i& z4 I: X6 _# b. Z" E- ^Material Group I CTI ³ 600
: d ?6 [& y1 y* A1 NMaterial Group II 400 £ CTI < 600" q$ K; b) ^& p5 }, n5 d
Material Group IIIa 175 £ CTI < 400& E( K+ n9 O3 _# {
Material Group IIIb 100 £ CTI < 175! c* `: H- }% d9 Y7 S
The material group is verified by evaluation of the test data for the material according to IEC
1 ?! S; B2 J' I; W/ N) d/ A60112 using 50 drops of solution A.
; r, I. Z3 s$ yIf the material group is not known, Material Group IIIb shall be assumed./ Q: v8 _2 _& p; i8 X' \- R& `
If a CTI of 175 or greater is needed, and the data is not available, the material group can be' ~8 B, N9 |' |& y; r- }
established with a test for proof tracking index (PTI) as detailed in IEC 60112. A material may% l! h% j: W; M! N8 _3 s m) r
be included in a group if its PTI established by these tests is equal to, or greater than, the lower% A9 b! m2 \1 g5 E& g
value of the CTI specified for the group.' g+ K2 [/ v: i( P( D
/ P! y% _: _" a3 T+ T——UL60950-1-2007 |
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