
1、 The inspection and testing of three-phase asynchronous motors mainly include: measurement of insulation resistance between windings to the casing and between windings; Measurement of DC resistance of windings in actual cold state; No load test; Dielectric strength test of winding to casing and winding to winding insulation; If necessary, conduct a dielectric strength test on the inter turn insulation of the winding. 2、 Inspection and test methods for three-phase asynchronous motors: a) Appearance inspection: Check whether the appearance is complete, whether the markings on the outlet end are correct, whether the fastening screws, bolts, and nuts are tightened, whether the rotor rotates flexibly, and what about the radial runout and vibration of the motor shaft extension. For wound rotor motors, the assembly quality of the brushes, brush holders, and collector rings should also be checked, as well as the good contact between the brushes and the collector ring. For enclosed self fan cooled motors, the exhaust system should be checked; b) Measurement of insulation resistance: For repaired motors, generally only the cold (room temperature) insulation resistance of the winding phase to phase and phase to ground should be measured. For wound rotor motors, the insulation resistance of the rotor winding should also be measured. For motors with multiple speed windings, the insulation resistance of each winding should be measured individually. Large motors can determine whether the windings are damp by measuring insulation resistance. For motors with a rated voltage below 500V, a 500V megohmmeter is generally used for measurement, and for motors between 500-3000V, a 1000V megohmmeter is used; Motors above 3000V use a 2500V megohmmeter. For motors below 500V, the insulation resistance should not be less than 0.5M Ω. All replaced windings should not be less than 5M Ω; c) Measurement of DC resistance: The measurement of DC resistance of motor windings is generally carried out in the cold state. The ratio of the error between the measured resistance values of each phase to the average value of the three phases shall not exceed 5%. If the difference in resistance values is too large, it indicates a short circuit, open circuit, poor welding or contact in the winding, or an incorrect number of turns in the winding. If the three-phase resistance exceeds the specified range, it indicates that the winding wires are too thin; d) Voltage withstand test: The stator winding of an electric motor can withstand a certain voltage without breakdown after being insulated with insulating material from phase to phase and from phase to ground. AC withstand voltage and DC withstand voltage are both withstand voltage tests, which are methods for evaluating the insulation strength of power equipment. DC withstand voltage test: The voltage is high and has a special effect on discovering certain local insulation defects, which can be conducted simultaneously with the leakage current test. Compared with AC withstand voltage test, DC withstand voltage test has the advantages of lightweight testing equipment, minimal insulation damage, and easy detection of local defects in the equipment. Compared with AC withstand voltage test, the main disadvantage of DC withstand voltage test is that due to the different voltage distribution inside the insulation under AC and DC, the DC withstand voltage test is not as close to the actual test of insulation as AC P>
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