29 Resistance to heat, fire and tracking
NOTE Annex J shows the selection and sequence of the tests of this clause.
29DV D1
Modification: Add the following note:
NOTE 1DV The tests are not made on parts of ceramic material, insulating parts of motors, such as shaft
insulation, end spiders, wedges, commutators, or brush-caps unless otherwise specified in the Part 2.
29.1 External parts of non-metallic material, parts of insulating material supporting live parts, including
connections and parts of thermoplastic material providing supplementary insulation or reinforced
insulation, the deterioration of which might cause the tool to fail to comply with this standard, shall be
sufficiently resistant to heat.
Compliance is checked by subjecting of the relevant parts to a ball-pressure test, which is made by means
of the apparatus shown in Figure 5.
Before starting the test, the part is maintained for 24 h in an atmosphere having a temperature between
15 °C and 35 °C, and a relative humidity between 45 % and 75 %.
The part is supported so that its upper surface is horizontal and the spherical part of the apparatus is
pressed against this surface with a force of 20 N. The thickness of the part under test shall be at least 2,5
mm.
The required thickness may be obtained by using two or more sections of the part.
The test is made in a heating cabinet at a temperature of (40
±
2) °C plus the maximum temperature rise
determined during the test of clause 12, but it shall be at least:
– for external parts (75
±
2) °C;
– for parts retaining live parts in position (125
±
2) °C.
Before the test is started, the test apparatus is brought to the temperature determined above.
After 1 h, the apparatus is removed and the part is immediately immersed in cold water so that it is cooled
to room temperature within 10 s. The diameter of the impression shall not exceed 2 mm.
For coil formers, only those parts which support or retain in position terminals or terminations are
subjected to the test.
Unless otherwise specified, parts operating at safety extra-low voltage not exceeding 24 V are not
considered to be live parts.
The test is not made on parts of ceramic material.
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