AC motors are inevitably malfunctioning due to friction, vibration, insulation aging, etc. during operation. If these faults are inspected, discovered and eliminated in time, they can effectively prevent accidents.
First, the failure check of the asynchronous motor
1. Listening to the sound, carefully looking for the fault point AC asynchronous motor is running, if you find a thin hum, there is no change in height, it is a normal sound, if the sound is thick, and there are sharp.The buzz is a precursor to a failure and should be considered for the following reasons:
(l) Core loosening The vibration of the motor during operation, the change of temperature will be high and low, which will deform the iron core fixing bolt, causing the silicon steel sheet to loosen and generate large electromagnetic noise.
(2) Rotor noise The sound produced by the rotation of the rotor, generated by the cooling fan, is a kind of humming sound, which is like the humming sound when the drum is hit. This is the speed change of the motor in sudden start, stop, reverse brake, etc. In the case, the acceleration torque causes the loosening of the rotor core and the shaft, and the lighter can continue to be used, and the heavy one can be opened for inspection and repair.
(3) Bearing noise In the operation of the motor, attention must be paid to the culture of the bearing sound. One end of the screwdriver is touched on the bearing cover, and the other end is attached to the ear. The sound inside the motor can be heard, different parts, different faults. , there are different voices. For example, the squeak is caused by the irregular movement of the gun inside the bearing, which is related to the clearance of the bearing and the state of the grease. The hum is the metal friction sound, which is generally caused by the lack of oil in the bearing. The bearing should be disassembled to add grease.
2. Using olfactory sensation, it is analyzed that the faulty motor has no odor during normal operation. If it smells different, it is a fault signal, such as burnt smell, which is caused by the insulation of the barbecue, and with the increase of the temperature of the motor, when it is serious, It will smoke; if it is oily, it is mostly the lack of oil in the bearing, and the odor of oil and gas evaporation when it is close to the dry grinding state.
3. Using the feel, check the fault, touch the outer casing of the TV by hand, you can roughly judge the level of the temperature rise. If you touch the motor casing with your hand, you will feel very hot. The temperature value is very high. Check the cause, such as excessive load, high voltage, etc. And then troubleshoot for the cause.
Second, the cause of common faults
1. The motor does not have a starting torque, or it cannot start when it is empty, and an abnormal sound is emitted. Reasons: (1) The three-phase power supply circuit (including the knife switch and the lead stator winding) has a phase disconnection, resulting in single-phase start. (2) The power supply voltage is too low. (3) The bearing is excessively worn, so that the rotor is close to one side of the stator, causing the stator and the rotor to be different, and the air gap is not uniform.
2. The starting torque of the motor is small, and it cannot be started when there is load. When the load increases, the motor stops, sometimes it emits strong noise and local heat. Reason: The grid voltage is low, the winding has a turn-to-turn short circuit, and there is a disconnection or de-soldering phenomenon in the rotor winding. After the start, the one-phase disconnection causes single-phase operation.
3. The starting current is large, and it is unbalanced, and the sound is loud, causing the protection device to operate and cut off the power. Cause: The stator winding wiring method may be incorrect, and the winding is grounded to the ground.
