When a fault occurs in the operation of the motor, the four methods of seeing, listening, smelling and touching can be used to prevent and eliminate the fault in time to ensure the safe operation of the motor.
1. look
Observe whether there is any abnormality during the operation of the motor, which is mainly manifested in the following situations.
1. When the stator winding is short-circuited, you may see smoke from the motor.
2. When the motor is seriously overloaded or running without phase, the speed will slow down and there will be a heavy "humming" sound.
3. The motor maintenance network is running normally, but when it stops suddenly, you will see sparks from the loose wiring; the fuse is blown or a part is stuck.
4. If the motor vibrates violently, it may be that the transmission device is stuck, the motor is not fixed properly, or the anchor bolts are loose.
5. If there are discoloration, burn marks and smoke traces at the contact points and connections in the motor, it may indicate local overheating, poor contact at conductor connections, or burnt windings.
2. listen
When the motor is running normally, it should emit a uniform and light "hum" sound, without noise or special sound.
If there is too much noise, including electromagnetic noise, bearing noise, ventilation noise, mechanical friction sound, etc., it may be a precursor or phenomenon of failure.
1. For electromagnetic noise, if the motor makes a high and low and heavy sound, there may be the following reasons:
(1) The air gap between the stator and the rotor is not uniform. At this time, the sound fluctuates from high to low and the interval between high and low sounds remains unchanged. This is caused by the wear of the bearing and the non-concentricity of the stator and the rotor.
(2) The three-phase current is unbalanced. This is due to misgrounding, short circuit or poor contact of the three-phase windings. If the sound is dull, it means that the motor is seriously overloaded or running with a lack of phase.
(3) The iron core is loose. During the operation of the motor, the fixing bolts of the iron core are loosened due to vibration, resulting in the loosening of the silicon steel sheet of the iron core and making noise.
2. For bearing noise, it should be monitored frequently during the operation of the motor.
The monitoring method is: put one end of the screwdriver against the bearing installation part, and the other end close to the ear, and you can hear the sound of the bearing running. If the bearing is in normal operation, the sound will be a continuous and small "rustling" sound, without fluctuating highs and lows and metal friction sounds.
If the following sounds appear, it is abnormal:
(1) There is a "squeak" 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 proper amount of grease.
(2) If there is a "chirp" sound, this is the sound made when the ball rotates. Generally, it is caused by dry grease or lack of oil, and an appropriate amount of grease can be added.
(3) If there is a "click" or "creak" sound, it is the sound produced 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 dryness of the grease.
3. If the transmission mechanism and the driven mechanism make continuous sound instead of fluctuating high and low, it can be dealt with in the following situations.
(1) The periodic "crack" sound is caused by the unevenness of the belt joint.
(2) The periodic "booming" sound is caused by the looseness between the coupling or the pulley and the shaft and the wear of the key or keyway.
(3) The uneven collision sound is caused by the blades colliding with the fan cover.
3. smell
Faults can also be judged and prevented by smelling the smell of the motor.Open the junction box and sniff.
Check to see if there is a burnt smell. If you find a special paint smell, it means that the internal temperature of the motor is too high; if you find a heavy burnt smell or burnt smell, it may be that the insulation layer has been broken down or the winding has been burned.
If there is no smell, it is necessary to use a megohmmeter to measure that the insulation resistance between the winding and the casing is lower than 0.5 megabytes, and it must be dried. If the resistance is zero, it means it is damaged.
4. touch
The cause of the fault can also be judged by touching the temperature of some parts of the motor.
In order to ensure safety, the back of the hand should be used to touch the motor casing and the parts around the bearing when touching by hand.
If abnormal temperature is found, the reasons may be as follows:
1. Poor ventilation. For example, the fan falls off, the ventilation channel is blocked, etc.
2. Overload. As a result, the current is too large and the stator windings are overheated.
3. Turn-to-turn short circuit of the stator winding or unbalanced three-phase current.
4. Frequent starting or braking.
5. If the temperature around the bearing is too high, it may be caused by bearing damage or lack of oil.
