Periodic maintenance of three-phase induction motor

In order to avoid and reduce the occurrence of sudden damage accidents of three-phase asynchronous motor, the three-phase asynchronous motor needs regular maintenance and overhaul. In case of overheating of motor and too low insulation of stator winding during use, it is necessary to stop immediately for overhaul. The maintenance method of three-phase asynchronous motor is to disassemble the motor, clean all parts first, then visually check them to see if there is any abnormality, and electrically check the motor winding. Specific inspection measures are as follows:

1. Mechanical inspection

Check whether the shell and end cover of the motor have cracks. If there are cracks, it shall be welded. Check whether the rotating shaft is bent and whether the assembly process is appropriate. In addition, move the rotor by hand to see if it can rotate. If it cannot rotate, see if there are foreign objects stuck and whether the bearing is in good condition, and then determine whether the bearing needs to be replaced according to the situation. Measure the shaft sleeve and check the upper and lower outer stops of the impeller, the retaining ring matched with them and the inner diameter of the motor. Whether these two mating clearances are within the maintenance standard range. If they exceed the tolerance, replace the parts or take other measures to make the mating clearance meet the specified requirements, otherwise the performance of the motor will be affected, and the axial balance force will be affected. Observe and check the performance of the rotor, especially pay attention to whether the weld is abnormal.

2. Electrical inspection

Check the DC resistance. The unbalance of the three-phase resistance shall not exceed 2%. Check the insulation resistance. The insulation resistance of the three-phase asynchronous motor winding can generally reach more than 100 Ω. If it is less than 5 Ω, analyze the cause, whether the insulation is damp, or the winding is grounded due to poor insulation. If there is no problem with the three-phase resistance balance through the bridge test, it is purely damp insulation and needs to be dried, If the three-phase resistance of the stator is unbalanced, the three-phase withstand voltage test and inter turn test of the motor coil shall be carried out respectively to find out the grounding point.