When the insulation resistance is lower than the specified value, the insulation of the winding machine is not good, but if the insulation resistance is higher than the specified value, it does not mean that the insulation of the winding machine must be good. Sometimes the insulation may have mechanical damage, but as long as there is no metal contact between the coil and the shell, its resistance may still be high. Monarch such as machine wire winding groove lining rupture, due to the fault of the air gap is still very high insulation resistance, so single megohm table has no medicine, check insulation quality is the most reliable method is withstanding voltage and insulation test. Insulation voltage test is divided into winding insulation test for the case and winding.

Winding insulation strength test, that is, winding over pressure test. During the test, 1.3 times the rated voltage is tested on the winding, which is maintained at 3min.

The test time can be shortened to lmin for the use of the winding machine, or the winding insulation part of the winding machine. Qualified winding machine should be able to withstand high voltage test, and winding turns insulation does not occur breakdown or breakdown.

AC motor insulation test cage motor must be carried out in the condition of no-load operation. Three phase asynchronous motor of the winding rotor, the rotor winding open circuit, when the rotor is stationary. Then rotor coil induced voltage will be higher than the rated voltage of 30%. That same inch test the rotor winding inter turn insulation.

For a multi speed motor, the winding of each of the rated speed should be tested. If it is a single winding, the maximum speed of the method can be tested only.

The motor for the speed test shall be carried out after the speed limit test.

Interturn insulation test in, if the interturn breakdown and damage will be fever, sometimes smell, smoke, three-phase current imbalance, according to the judge the interturn insulation. Test voltage can be obtained by transformer or voltage regulator.

In the inter turn insulation test of DC motor, the speed of the motor can be improved while the speed of the motor is increased, but the value of the speed should not exceed 115%. For a DC motor with a more than two ends, the test voltage should be raised to make the voltage between the adjacent two - direction sheets not exceed 24V condition.

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