IEC 60172-2015 pdf free download.Test procedure for the determination of the temperature index of enamelled and tape wrapped winding wires.
time to failure
number of hours to failure calculated from the specimen failure times for a set of specimens at one exposure temperature
4 Summary of procedure
A set of specimens in accordance with Clause 5 is subjected to a testing cycle. This cycle consists of a heat-storing period at a temperature given in Clause 6. followed by a proof voltage test at room temperature in accordance with Clause 7.
This cycle is repeated until a sufficient number of specimens has failed, The time to failure is calculated in accordance with Clause 8. The test is carried out at three or more temperatures. A regression line is calculated in accordance with 8.4 and the time to failure values plotted on thermal endurance graph paper as a function of the exposure temperature.
The temperature in degrees Celsius, corresponding to the point of intersection of the regression line with the ordinate of 20 000 h endurance represents the temperature index of the winding wire under test.
5 Test specimens
5.1 Preparation
5.1.1 Enamelled round wire with a nominal conductor diameter of 0,224 mm up to and including 2.65 mm
The grade of insulation used for determining the thermal index shall be grade 2 or grade 2B for self-bonding winding wires.
Wire sizes 0.315 mm and 0.28 mm are permitted for use when the specification size range is limited to 0,50 mm and finer.
NOTE For round enamelled winding wires, in order to avoid undue fragility of the test specimen. experience has shown that nominal conductor diameters of 0.800 mm up to and including 2.65 mm are generaliy found convenient to handle and test.
Specimens shall be prepared as follows:
a) A wire specimen approximately 400 mm in length shall be twisted together over a distance 01125mm with a device as shown in Figure 1. The force tweight) applied to the wire pair while being twisted and the number of twists are specified in Table 1.IEC 60172 pdf download.