Inspection and elimination of common faults of the

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Inspection and elimination of common faults of AC motor. If these faults are checked and found in time, the material can be more effectively prohibited and eliminated, and accidents can be effectively prevented

I. fault inspection of asynchronous motor

1 Listen to the sound and find out the fault point carefully. During the operation of AC asynchronous motor, if a thin buzzing sound is found, and there is no change from high to low, it is a normal sound. If the sound is thick, and there is a sharp buzzing and hissing sound, it is a precursor of the fault. The following reasons should be considered:

(L) the vibration of the motor with loose iron core during operation, and the change of temperature from high to low, will deform the iron core fixing bolts, resulting in the loosening of silicon steel sheets, Generate large electromagnetic noise

(2) rotor noise the sound generated by the rotor rotation is a kind of whine generated by the cooling fan, which is like the thumping sound when the drum is beating. This is caused by the loose fit between the rotor core and the shaft caused by the acceleration torque when the motor changes speed suddenly, stops, reversely brakes, etc. the light one can continue to use, and the heavy one can be disassembled for inspection and repair

(3) bearing noise during the operation of the motor, attention must be paid to the bearing sound culture. Touch one end of the screwdriver on the bearing cover and stick the other end to the ear. You can hear the sound changes inside the motor. Different parts and different faults have different sounds. Such as creaking, which is caused by the irregular movement of the rolling gun in the bearing and is related to the bearing clearance and grease status. The hissing sound is the sound of metal friction, which is generally caused by the lack of oil in the bearing. The bearing should be disassembled to add grease, etc

2. Using bromine sense, it is analyzed that there is no peculiar smell in the normal operation of the faulty motor. If strange smell is detected, it is a fault signal, such as burnt smell, which is caused by the barbecue of insulation, and will smoke with the increase of motor temperature in serious cases; For example, the smell of oil burning is mostly caused by the lack of oil in the bearing and the peculiar smell caused by the evaporation of oil and gas when approaching the dry grinding state

3. Use the hand feeling to check the fault. The important requirement of the hand, especially the high stiffness precision spring, is to touch the shell of the TV with high testing accuracy, which can roughly judge the temperature rise. If the hand feels very hot when touching the motor shell, and the temperature value is very high, check the causes, such as excessive load and high voltage, and then eliminate the fault according to the causes

II. The cause of common faults is the earliest

1 The motor has no starting torque, or cannot be started under no-load, and makes abnormal sound. Cause:

(L) one phase of three-phase power supply circuit (including knife switch and lead stator winding) is powered off, resulting in single-phase startup

(2) the power supply voltage is too low

(3) the bearing is excessively worn, which makes the rotor close to the stator, resulting in non concentricity between the stator and the rotor and uneven air gap

provide a good environment for project construction 2 The starting torque of the motor is small, so it cannot be started when there is load. When the load increases, the motor stops, sometimes makes strong noise, and local heating. Cause: the electric voltage is low, the winding has inter turn short circuit, the rotor winding is broken or desoldered, and one phase is broken after startup, resulting in single-phase operation

3. The starting current is large, unbalanced and loud, causing the protection device to act and cut off the power supply. Cause: the wiring method of stator winding may be incorrect, and the insulation of winding to ground is aging

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