IEC 60172-2020 pdf download.Test procedure for the determination of the temperature index of enamelled and tape wrapped winding wires.
With the specimen in the vertical position, it shall be immersed in the impregnating agent for (60 ± 1 0) s. It shall be removed slowly and uniformly at a rate of about 1 mm/s. It shall be drained horizontally for 1 0 min to 1 5 min and cured horizontally according to the manufacturer’s recommendation or to an agreed schedule. If more than one treatment is to be given, immerse, drain and cure the specimen vertically reversing the specimen for each subsequent treatment. NOTE 2 Some impregnating agents, such as high viscosity or thixotropic products require alternative processing methods.
5.3 Notes on number of test specimens The accuracy of the test results depends largely upon the number of test specimens aged at each temperature. A greater number of test specimens is required to achieve an acceptable degree of accuracy if there is a wide spread in results among the specimens exposed at each temperature. Experience has shown that twenty specimens without impregnation and ten specimens with impregnation give results with an acceptable tolerance. A minimum of ten specimens shall be used.
5.4 Specimen holder
5.4.1 For specimens according to 5.1.1 Since individual handling of the twisted specimens may result in premature failures, it is recommended that the specimens be placed in a suitable holder, as shown in Figure 8. The holder should be designed in a manner that will protect the twisted specimens from external mechanical damage and warping. The holder will be so constructed as to allow the ends of the twist to protrude from the holder to make electrical connections for proof testing. The holder shall be designed for at least ten specimens to decrease handling time.
5.4.2 For specimens according to 5.1.2
The specimen shall be hung in the oven. No special holder is required.
6 Temperature exposure Test specimens shall be subjected to the temperatures given in this Clause 6. The test temperature and time of exposure in each cycle are given in Table 3. A test cycle is defined as one exposure to a high temperature followed by one proof-voltage test at room temperature (20 – 30 °C). The test specimens shall be placed directly into and removed from the ageing ovens without controlling the heating or cooling rate. The ovens shall be heated to the proper temperatures before the specimens are subjected to the exposure temperature. The specimens shall be aged in a forced air circulation oven which is capable of maintaining the temperature of the specimens under test within 2 °C of the selected exposure temperature. The exposure times are selected to subject the test specimens to approximately 1 0 cycles at each temperature before the time to failure is reached.IEC 60172 pdf download.