AC motor common faults and their causes

In the operation of AC motors due to insulation, aging, friction, vibration and other reasons, it is inevitable that failure occurs. We can effectively prevent accidents by checking, detecting and rectifying these faults in a timely manner.

One, asynchronous motor fault check

1. Listen to the sound and carefully find the point of failure. When the AC asynchronous motor is running, if it finds a small squeak, it doesn't change suddenly, it is a normal sound; on the contrary, if the sound is thick, and there are sharp squeaks and squeaks, it is faulty. Aura, consider the following reasons:

(l) Loose cores, vibration of the motor during operation, and changes in temperature will cause deformation of the iron core fixing bolts, resulting in loosening of the silicon steel sheet and large electromagnetic noise.

(2) Rotor noise The sound produced by the rotation of the rotor, generated by the cooling fan, is a kind of buzzing noise, which is like the buzzing sound when the drum is beaten. This is the sudden start, stop, and reverse braking of the motor. Under the circumstances, the acceleration torque causes the rotor iron core to loosen with the shaft, and the lighter ones can continue to use, and the heavy ones are opened for inspection and repair.

(3) Bearing noise During operation of the motor, attention must be paid to the culture of bearing noise. Touch the end of the screwdriver on the bearing cover and the other end to the ear. You can hear the internal sound of the motor, different parts, and different faults. There are different voices. Such as squeaking sound, is the irregular movement of the roller inside the bearing, it is related to the bearing clearance, grease status. The buzzing sound is metal friction sound, which is generally caused by the lack of oil in the bearing, so the bearing should be disassembled and grease added.

2. The use of olfactory, analysis of faulty motor in normal operation is no peculiar smell; if you smell the difference, it is the fault signal: such as Jiaozhewei, is issued by the insulation barbecue, and with the increase of motor temperature, serious Smoke is also emitted when the oil is burnt; most of the oil is bearing oil, and the odor of vaporization of oil and gas occurs near the state of dry grinding.

3. Use your hand to check for problems. Touch the shell of the TV with your hand to roughly determine the temperature rise. If you touch the motor shell with your hand, it will feel very hot and the temperature value is very high. You should check the reasons, such as: overload, high voltage, and then eliminate the cause. malfunction.

Second, the cause of common failures

1. The motor does not start torque, or it can not start when no load, and an abnormal sound is emitted. Reasons: (l) The three-phase power supply circuit (including the knife switch and the wire-wound stator winding) has one phase of power failure, causing single-phase startup. (2) The power supply voltage is too low. (3) The excessive wear of the bearing causes the rotor to approach one side of the stator, causing the stator and rotor to be of different concentricity and uneven air gap.

2. The motor starting torque is small, and it cannot be started when there is load. When the load increases, the motor stops, and sometimes it emits strong noise and local heating. Causes: The grid voltage is low, the windings have short circuits in the turns, and the rotor windings are broken or disconnected. After the start-up, one-phase breakage causes single-phase operation.

3. The starting current is large and unbalanced and the sound is loud, causing the protection device to operate and cut off the power supply. Cause: The stator winding wiring method may not be correct and the windings are insulated against the ground.

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