IEC 60172-2015 pdf free download – Test procedure for the determination of the temperature index of enamelled and tape wrapped winding wires.
Care shall be taken that the centre section shows a close contact between the two pieces.
After tying, further bending of the ends shall be avoided.Pre-annealing of the specimen priorto testing or impregnating will remove stress and craze marks and therefore may be desirablewith certain material.
e) Prior to testing the specimen shall be proof-tested at 1 00o v a.c.
5.2Varnish impregnation
Experience has shown that insulated wire according to lEC 60317 and impregnating agentsaccording to lEC 60455-3-5 or lEC 60464-3-2 can affect one another during the thermalageing process.
NOTE 1 Testing varnished specimens will allow for evaluation of the compatibility of the wire insulation with animpregnating agent. Thus the temperature indices of different combinations can be compared.
Interaction between wire insulation and such agent may increase or decrease the relativethermal life of this combination compared with the life of the wire tested without impregnation.Therefore，with impregnated specimens， this test procedure may give an indication of thethermal endurance of a combination of wire insulation and impregnating agent.
lf such impregnation is required, the following procedure shall be applied:
With the specimen in the vertical position, it shall be immersed in the impregnating agent for(60±10) s (see note). lt shall be removed slowly and uniformly at a rate of about 1 mm/s. Itshall be drained horizontally for 10 min to 15 min and cured horizontally according to themanufacturer’s recommendation or to an agreed schedule. If more than one treatment is to begiven，immerse，drain and cure the specimen vertically reversing the specimen for eachsubsequent treatment.
NOTE 2 Some impregnating agents, such as high viscosity or thixotropic products require alternative processingmethods.
5.3 Notes on number of test specimens
The accuracy of the test results depends largely upon the number of test specimens aged ateach temperature. A greater number of test specimens is required to achieve an acceptabledegree of accuracy if there is a wide spread in results among the specimens exposed at eachtemperature.
Experience has shown that twenty specimens without impregnation and ten specimens withimpregnation give results with an acceptable tolerance. A minimum of ten specimens shall beused.
5.4Specimen holder
5.4.1 For specimens according to 5.1.1
Since individual handling of the twisted specimens may result in premature failures,it isrecommended that the specimens be placed in a suitable holder, as shown in Figure 8.Theholder should be designed in a manner that will protect the twisted specimens from externalmechanical damage and warping.The holder will be so constructed as to allow the ends ofthe twist to protrude from the holder to make electrical connection for the proof testing asshown in Figure 9. The holder shall be designed for at least ten specimens to decreasehandling time.
5.4.2For specimens according to 5.1.2
The specimen shall be hung in the oven. No special holder is required.
6 Temperature exposure
Recommended temperatures to which the test specimens are subjected are given in thisClause 6.
In Table 3, the recommended temperature and time of exposure in each cycle are given.Atest cycle is defined as one exposure to a high temperature followed by one proof-voltage testat room temperature (2o·C – 30°C). The test specimens shall be placed directly into andremoved from the ageing ovens without controlling the heating or cooling rate.
The ovens should be heated to the proper temperature before the specimens are subjected tothe exposure temperature.
The specimens should be aged in a forced air circulation oven which is capable of maintainingthe 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 10 cycles ateach temperature before the time to failure is reached.IEC 60172 pdf download.