Cable detection method and means
●Resistance detection: Use a resistance detector or a double-arm bridge to sample 1m, and measure and calculate the resistance at 20 °C. See specific example (1):
In the formula:
R20-20 ° C resistance per kilometer length, the unit is Ω / km;
Rx-t °C L length cable measured resistance value, the unit is Ω:
L—measured length of the sample in m
T—the conductor temperature at the time of measurement (according to the ambient temperature) in °C
● Power frequency voltage test: The cable should be subjected to the power frequency withstand voltage test of the specified voltage (the specified value in the standard). Take 1 sample of not less than 5m on the test cable, and remove one end of the sample (about 10mm). When removing, do not damage other insulation. Soak the sample in the room temperature sink. The water surface should be no less than 200mm, and it is guaranteed that flashover discharge along the surface does not occur under the specified test voltage. After the sample was immersed in water for 1 hour, the specified voltage was applied using a power frequency withstand voltage tester, and the breakdown was maintained for 5 minutes.
For this requirement, better lead manufacturers will add necessary monitoring instruments in the production process, and monitor them through spark test and insulation thickness test.
● Structure detection. According to the standard regulations, the linear shape, wire diameter, and round sheathed cable are measured at the same cross section. The difference between the outer diameters of any two points should not exceed 15% of the upper limit of the average outer diameter.
● Bending test. No visible cracking or other damage shall occur after bending according to the specified mandrel, and it shall be able to withstand the water immersion withstand voltage test specified in the standard.
● Thermal effect, solvent resistance test. These two test items are used as test items for cable manufacturers, and motor manufacturers do not conduct such tests in principle.
● Impregnating paint test. Because different impellers used by different motor manufacturers are different, the drying process parameters are not the same. It is recommended that the motor manufacturer carry out the test of the project. Do not change the cable supplier frequently after passing the test; the cable manufacturer is in the material or processing technology. After the change, you should communicate with the motor manufacturer in time to prevent the failure.
● Length, appearance and logo. The requirements of the standard are stipulated. The delivery length of the cable with a nominal section of not more than 35mm2 is not less than 50m. In principle, no breakage occurs. Most manufacturers implement 100m in a single package. The standard stipulates that the cable should have continuous marks such as the manufacturer's name, cable type and voltage level. The mark should be clear and can withstand light rubbing of not less than 10 times of water-impregnated cotton.
As a motor manufacturer, the choice of leads should be controlled by the control of the purchase channel, rather than through complicated inspections. However, as an important key component of motor products, we cannot ignore the quality control of the leads.
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