When the motor is running or malfunctioning, it can prevent and eliminate the fault in time by watching, listening, smelling and touching four ways to ensure the safe operation of the motor.
Observe the presence or absence of abnormalities during the operation of the motor, which is mainly manifested in the following cases.
a. When the stator winding is short-circuited, the motor may see smoke.
b. When the motor is heavily overloaded or lacks phase operation, the speed will be slower and there will be a heavier "click" sound.
c. The motor maintenance network operates normally, but when it stops suddenly, it will see a spark at the loose connection; the fuse is blown or a part is stuck.
d. If the motor vibrates violently, it may be that the transmission is stuck or the motor is not properly fixed, and the foot bolts are loose.
e. If there are discoloration, burn marks and smoke marks on the contact points and joints in the motor, it may indicate local overheating, poor contact at the conductor connection or burnt of the winding.
When the motor is running normally, it should emit a uniform and light "click" sound, no noise and special sound. If the noise is too large, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction, etc., it may be a malfunction or failure phenomenon.
a. For electromagnetic noise, if the motor makes a loud, high, and heavy sound, the reasons may be as follows:
(1) The air gap between the stator and the rotor is not uniform. At this time, the sound is high and low and the interval between the high and low sounds is constant. This is caused by the wear of the bearing and the difference between the stator and the rotor.
(2) Three-phase current imbalance. This is the reason that the three-phase winding has a wrong grounding, short circuit or poor contact. If the sound is very dull, the motor is seriously overloaded or lacks phase operation.
(3), the core is loose. When the motor is running, the iron core fixing bolt is loosened due to vibration, and the iron core silicon steel sheet is loosened to emit noise.
b. For bearing noise, it should be monitored frequently during motor operation. The monitoring method is: the end of the screwdriver is placed against the bearing installation part, and the other end is close to the ear, and the bearing running sound can be heard. If the bearing is running normally, its sound is continuous and small "sand" sound, there will be no change in height and friction and metal friction.
If the following sounds occur, it is abnormal:
(1) There is a "beep" sound when the bearing is running. This is the metal friction sound, which is generally caused by the lack of oil in the bearing. The bearing should be disassembled and filled with a proper amount of grease.
(2) If there is a "beep" sound, this is the sound that is emitted when the ball rotates. Generally, it is caused by dry grease or lack of oil. It can be filled with proper amount of grease.
(3) If there is a "snake" sound or a "click" sound, it is the sound generated by the irregular movement of the balls in the bearing. This is caused by the damage of the balls in the bearing or the long-term use of the motor, and the grease is dry.
c. If the transmission mechanism and the transmission mechanism emit sounds that are continuous rather than high and low, they can be handled in the following situations.
(1) The periodic "beep" sound is caused by the unevenness of the belt joint.
(2) Periodic "beep" sound, caused by loose coupling between the coupling or pulley and the shaft, and wear of the key or keyway.
(3) Uneven collision sound is caused by the fan blade colliding with the fan cover.
The fault can also be judged and prevented by smelling the smell of the motor. Open the junction box and sniff with your nose. Look for a burnt smell. If a special paint smell is found, the internal temperature of the motor is too high. If a heavy paste or burnt smell is found, the insulation layer may be broken or the winding may be burnt. If there is no taste, it is necessary to measure the insulation resistance between the winding and the outer casing to less than 0.5 mega megameter, and it is necessary to carry out drying treatment. The resistance is zero, indicating that it is damaged.
Touching the temperature of some parts of the motor can also determine the cause of the malfunction.
In order to ensure safety, the back of the hand should be touched by the hand to touch the motor casing and the surrounding part of the bearing.
If the temperature is abnormal, the reasons may be as follows.
(1). Poor ventilation. Such as the fan is off, the air duct is blocked.
(2). Overload. The current is too large to overheat the stator windings.
(3). Stator winding turn-to-turn short circuit or three-phase current imbalance.
(4). Frequent start or brake.
(5). If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.
The motor bearing stipulates that the maximum temperature of the rolling bearing does not exceed 95 °C,
and the maximum temperature of the sliding bearing does not exceed 80 °C. And the temperature rise does not exceed 55 ° C
(temperature rise is the bearing temperature minus the ambient temperature at the test).