How to deal with the fault of three-phase asynchronous motor
Release time：2020-05-08 15:43Number of views：Originate：
The faults of three-phase asynchronous motor can be generally divided into two categories. One is electrical faults, such as the faults of various types of switches, buttons, fuses, brushes, stator windings, rotors and starting equipment. The other is mechanical failure, such as bearing, fan blade, casing, coupling, end cover, bearing cover, shaft, etc. Follow the manufacturers of three-phase asynchronous motor to see the most common faults and solutions.
When the motor fails, there will be some abnormal phenomena
Such as temperature rise, excessive current, vibration and abnormal sound. In order to check and remove the motor fault, carefully observe the motor to understand the abnormal phenomenon after the fault. Then through the abnormal analysis of the causes, find out the fault, and finally eliminate the fault.
The following are common accumulated faults and maintenance methods of three-phase asynchronous motor
Seven common faults of motor
Motor does not rotate
Motor speed below rated
Motor case charging
Abnormal motor sound
Motor Bearing Overheating
Motor temperature too high
Too many sparks on slip ring of winding motor
● the motor does not rotate and the analysis power supply is not connected
If the power supply is not connected or in poor contact, the motor will not rotate. At this time, the electrician should check the switch, fuse, various contacts and connectors, and gradually check the fault for maintenance.
When starting, the fuse of the fuse will not rotate: find out the cause of the fuse, check the fault and match the fuse of the same specification according to the motor capacity;
The setting current of over-current relay is too small to turn off: at this time, the setting current should be increased appropriately;
If the driving mechanism is too loaded or stuck, it will not rotate: select the motor with large capacity or reduce the load, and check the condition of the driving mechanism;
Stator or rotor winding open circuit causes no rotation: open the junction box, and use the multimeter ohmmeter to check whether the motor winding is open circuit (broken wire). If there is an open circuit, an abnormal resistance value will occur. The motor needs to be opened to further check the disconnection point and the correct connection.
Inter turn short circuit of stator winding: the winding type of motor consists of multi turn coils. When the coil is shorted, the motor may not rotate. Use a multimeter to check and locate the shorted compartment. Disconnect the connecting wires of each coil of one phase of the motor, check the short circuit points in groups, find out and re insulate.
Stator winding short circuit to ground: check the grounding winding with megger or multimeter. If the insulation is damaged, re insulate it. If it is serious, replace the winding. If it is wet, it can be dried and then coated with insulating paint.
Stator winding connection error: remove the motor to find out the error and reconnect.
Poor contact of rotor slip ring of winding motor: slip ring correction indicates adjustment of carbon brush pressure.
● motor speed below rated value
Low power supply voltage: low voltage will cause insufficient motor power, so when the belt is loaded, the motor speed is lower than the rated value. At this time, you can use a voltmeter or multimeter to measure the input voltage of the motor.
Overload: at this time, the motor with larger capacity shall be selected or the load shall be reduced;
Broken bars of squirrel cage rotor: after removing the first 1 and 2 bars, disassemble the motor for inspection, find out the broken bars and weld them.
Single phase open circuit of wound rotor: use multimeter to find out the open circuit and reconnect;
Poor contact of starting resistance of wound rotor motor: repair the contact of rheostat or replace the rheostat;
Poor contact between the slip ring of the winding rotor and the carbon brush: adjust the pressure of the carbon brush and improve the contact surface of the slip ring of the carbon brush.
● motor housing charged
The reasons for the electrification of the three-phase asynchronous motor shell may be: This indicates that your motor shell is not grounded or damaged, after the grounding device is damaged, the motor winding is damped, the insulation is aging, resulting in poor insulation and leakage, or the lead is connected with the motor shell.
In this case, first check whether the grounding device of the motor is intact and re ground. Dry the motor and replace the winding with severely aged insulating material.
● motor abnormal sound
Two phase operation has buzzing sound: restart after shutdown. If it is two-phase operation, the motor will no longer rotate, find out the cause of phase loss and eliminate it;
Three phase current imbalance: check whether the three-phase power supply imbalance is caused by the power supply voltage or the motor itself, find out the causes and eliminate them;
Friction between the stator and the rotor: correct the rotor shaft, file the protruding part of the stator or rotor core, or renew the bearing;
Some screws or parts are loose: tighten screws and black gold connecting bolts;
Vibration: check whether the foundation is stable, tighten the screws at the bottom of the motor, and check the balance of the rotor.
Collision of fan blade shell: correct the blade and tighten the screws;
Serious oil shortage of bearing: clean the bearing and install new lubricating oil. The capacity shall not exceed 70% of the capacity.
● Motor Bearing Overheating
Bearings and shafts too loose (walking in the inner garden) or too tight: too loose or too tight will cause excessive friction, which will increase the temperature of the motor bearings. For the shaft too loose, the sleeve can be inserted; for the shaft too tight, the shaft can be reprocessed to the standard size;
The bearing and end cover are too loose (round) or too tight: when the bearing and end cover are too loose, insert the end cover, too tight is the standard size for reprocessing;
Too much or too little bearing lubricating oil or poor oil quality: add proper amount of lubricating oil or change oil;
Bearing damage: replace the bearing.
Motor temperature too low and too high
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