28 Creepage distances, clearances and distances through insulation
28.1 Creepage distances and clearances shall not be less than the values in millimetres shown in Table
10. The values specified in the table do not apply to cross-over points of motor windings.
If a resonance voltage occurs between the point where a winding and a capacitor are connected together,
and metal parts which are separated from live parts by basic insulation only, the creepage distance and
clearance shall not be less than the values specified for the value of the voltage imposed by the
resonance, these values being increased by 4 mm in the case of reinforced insulation.
Compliance is checked by measurement.
For tools provided with an appliance inlet, the measurements are made with an appropriate connector
inserted; for tools with type X attachment, they are made with supply conductors of the largest
cross-sectional area specified in 25.2, and also without conductors; for other tools, they are made on the
tool as delivered.
For tools provided with belts, the measurements are made with the belts in place, and the devices
intended for varying the belt tension adjusted to the most unfavourable position within their range of
adjustment, and also with the belts removed.
Movable parts are placed in the most unfavourable position; nuts and screws with non-circular heads are
assumed to be tightened in the most unfavourable position.
The clearances between terminals and accessible metal parts are also measured with the screws or nuts
unscrewed as far as possible, but the clearances shall then be not less than 50 % of the value shown in
Table 10.
Distances through slots or openings in external parts of insulating material are measured to metal foil in
contact with the accessible surface; the foil is pushed into corners and the like by means of the standard
test finger of Figure 1, but it is not pressed into openings.
If necessary, a force is applied to any point on bare conductors, other than those of heating elements, to
any point on uninsulated metal capillary tubes of thermostats and similar devices, and to the outside of
metal enclosures, in an endeavour to reduce the creepage distances and clearances while taking the
measurements.
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