4.4 Measuring the clearance and creepage distances
(based IEC 60664-1)
The groove width specified the examples applies
to all examples function the pollution degree follows:
4 Insert 169
Table 4.6.
Degree
o Pollution
Groove width X
Minimum values
1 0.5 mm
If the associated clearance less than mm, the minimum groove width
may reduced one-third this clearance. These cases not differentiate between
gaps and grooves between types insulation.
Thefollowing assumptions are made:
- any recess assumed bridged with insulating peg having a
length equal the specified width and being placed the most
unfavourable position (see example 3);
- where the distance across groove equal larger than the
specified width the creepage distance measured along the contours
of the groove (see example 2);
- creepage distances and clearances measured between parts which can
assume different positions relation each other, are measured when
these parts are their most unfavourable position.2.25 mm
2 1.0 mm
3 1.20.
Rule: Creepage and clearance distance are measured directly across
the groove shown
Clearance distance:--------— Creepage distance:
.
Fig.201: Example 1:
< mm
1 1--------------------------- T
Condition: Path under consideration includes parallel- converging
sided groove any depth with width less than mm. 4.5 mm
4 2.
The methods measuring creepage distances and clearances are indicated
in the following examples 11
