Annex A – (normative) – Measurement of creepage distances and clearances
A.1 Measurement of creepage distances and clearances
The methods of measuring creepage distances and clearances, which are specified in 28.1, are indicated
in cases 1 to 10 (see Figure A.1).
These cases do not differentiate between gaps and grooves, or between types of insulation.
The following assumptions are made:
– a groove may have parallel, converging, or diverging sides;
– any groove having diverging sides, a minimum width exceeding 0,25 mm, a depth exceeding 1,5 mm,
and a width at the bottom equal to or greater than 1 mm, is regarded as an air gap across which no
creepage path exists (case 8);
– any corner including an angle less than 80° is assumed to be bridged with an insulating link of 1 mm
width (0,25 mm for dirt-free situations), moved into the most unfavourable position (case 3);
– where the distance over the top of a groove is 1 mm (0,25 mm for dirt-free situations) or more, no
creepage distance exists across the air gap (case 2);
– creepage distances and clearances measured between parts moving relative to each other are
measured when these parts are placed in their most unfavourable stationary positions;
– any air gap less than 1 mm wide (0,25 mm for dirt-free situations) is ignored in computing the total
clearance.
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