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The general tests of electric motors：3

3. Voltage withstand test of the motor:
Ac voltage withstand test is the most direct method to identify the insulation strength of electrical equipment. It is of decisive significance to judge whether the electrical equipment can be put into operation. It is also an important means to ensure the insulation level of equipment and avoid insulation accidents.
After the insulation treatment between the stator windings and each phase and the housing, the motor should be able to withstand a certain voltage without being broken down.Ac voltage withstand test is the most direct method to identify the insulation strength of electrical equipment. It is of decisive significance to judge whether the electrical equipment can be put into operation, because ac voltage withstand test can fully reflect the actual situation of electrical equipment operating under ac voltage, and can truly and effectively find insulation defects.
Ac voltage withstand test is a destructive test, compression test needs to be done on the special test bench.Each winding should take turns to do insulation test stand. Then a pole of the test power connect with the leading of the winding line, and the other pole connected on the ground base of motor. And when test a winding, the other windings on the electrical should be connected to ground base.
Apply a certain value of 50Hz ac voltage to the frame and each phase of the winding, which lasts for 1min and is considered qualified while without breakdown. Test voltage standard of low-voltage motor: 1KW or less, effective value is 2UN+500V;1.1kw ~3KW, the effective value is 1500V;4KW and above, the effective value is 2UN+1000V.
Test voltage standard of high-voltage motor:
When carrying out the voltage withstand test, the boost must start from zero, and the impact closing is not allowed. The boost speed can be arbitrary before 75% of the test voltage, and the boost shall be uniform after 75% of the voltage, which is about 2% of the test voltage per second.Besides, safety must be paid attention to to prevent electric shock accidents. For motors whose rated voltage is less than 380V, if there is no high voltage test equipment around, the voltage withstand test after assembly can also be replaced by 2500V megameter test for 1min.Absolute attention must be paid to personal safety during the test. At the end of the test, the quilt specimen must be fully discharged before it can be touched.

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