IEC 60172:2020 pdf free download

IEC 60172:2020 pdf free download Test procedure for the determination of the temperature index of enamelled and tape wrapped winding wires
3.2
specimen failure time
number of hours at the exposure temperature that have elapsed at the time a specimenfails the proof test
3.3
time to failure
number of hours to failure calculated from the specimen mean value or logarithmic meanvalue failure times for a set of specimens at one exposure temperature，in accordance with8.2
4Summary of procedure
A set of specimens in accordance with Clause 5 is subjected to a testing cycle. This cycleconsists of a heat-exposure period at a temperature given in Clause 6, followed by a proofvoltage 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 iscalculated in accordance with Clause 8. The test is carried out at three or moretemperatures. A regression line is calculated in accordance with 8.4 and the time to failurevalues plotted on thermal endurance graph paper as a function of the exposuretemperature.
The temperature in degrees Celsius,corresponding to the point of intersection of theregression line with the ordinate of 20 000 h endurance represents the temperature index ofthe winding wire under test.
5 Test specimens5.1Preparation
5.1.1 Enamelled non-tape wrapped round wire
This procedure applies to enamelled round wires that are not tape wrapped. The thermalindex can be determined by evaluating enamelled non-tape wrapped round wire with anominal conductor diameter of 0,224 mm up to and including 2,65 mm.
NOTE For round enamelled winding wires, experience has shown that nominal conductor diameters of 0,800 mmup to and including 1,60 mm are generally found convenient to handle and test.
Wires with a nominal conductor diameter between 0,280 mm and 0,500 mm are permitted foruse when the specification range of diameters is limited to 0,500 mm and finer.
The grade of insulation used for determining the thermal index shall be grade 2 or grade 2Bfor self-bonding winding wires.
Specimens shall be prepared as follows:
a) A wire specimen approximately 400 mm in length shall be twisted together over a distanceof 125 mm with a device as shown in Figure 1.The force (weight) applied to the wire pairwhile being twisted and the number of twists are specified in Table 1.