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Motor fault? Perhaps most old electricians have never met

1、 Last month, a burning fault of 22KW three-phase asynchronous motor occurred in our unit. At the time of the accident, the motor sent out extremely violent vibration. At the same time, dazzling electric sparks burst out from the motor cavity, and flames sprang up. As for the sound made by the scene at that time, it turned pale!

After the power was cut off to put out the fire, the author and colleagues took the motor apart - except for the ablation marks, there were two obvious friction marks on the stator tail winding of the motor, so that the two windings showed a clear state! And the whole winding shows signs of being pulled! After careful inspection, we finally found the cause of the problem: during the rewinding process of the motor, the unit motor maintenance worker (specially designed) did not fasten the joint firmly when using white cloth belt for shaping and binding. During the use process, due to the action of vibration and rotor blades, one end of the joint was loosened and drawn into the rotor shaft, resulting in failure!

2、 On the 8th of this month, a 7.5kW three-phase asynchronous motor in the unit production line was burnt out due to "lack of phase". After investigation, the main cause of the fault is still directly related to the improper assembly operation of relevant personnel: it turns out that during the overhaul and assembly of the motor, Cause one phase outgoing line of motor winding (the inside of the motor has formed a Y shape) was pressed to the bottom of the wiring room! Only because the crimping is not serious, there is no abnormality during the initial use. but with the influence of various mechanical vibration and other factors during the use time, the insulation layer of the phase outgoing line is worn through, resulting in single-phase grounding fault. However, the operator on duty lacks experience in dealing with this fault Power on the motor for a long time, resulting in irreversible phase loss and burning failure!

3、 In May, a 45KW three-phase asynchronous motor in the same unit had leakage fault. After inspection, it was found that the cause of the fault was very speechless: the motor winding had been burned earlier, so it was repaired and rewound. However, due to poor rewinding technology and too rough wire embedding process, the rewinding winding is too long and improper shaping, resulting in direct contact between the winding at the shaft extension end and the end cover! Therefore, the vibration and friction in the process of use destroy the insulation layer on the winding surface and induce leakage fault!


4、 Also in May, a 30kW motor in use in the unit next door broke down seriously, resulting in the scrapping of the whole machine! It turned out that some time before the fault occurred, the motor made occasional "Ho, Ho" sound, but because the sound was very small, the colleagues of the unit ignored it. On the day of the incident, the noise of the motor increased, but the operator did not report in time because it had been ignored before. Results suddenly, the motor made a loud noise, and there were sparks from violent metal friction and collision in the machine! After inspection, it was found that the ball bearing at the shaft extension end of the motor had "loose disk" phenomenon!