Common faults and maintenance methods of 11 three-phase asynchronous motors
As a professional in the maintenance industry, I should not be unfamiliar with equipment such as three-phase asynchronous motors, right? For common faults and corresponding maintenance measures of such equipment, Xiaoyi has compiled some content to share with everyone. Let's take a look together!
1, Abnormal noise and abnormal noise during motor operation
1. Cause of malfunction
① Friction between rotor and stator insulation paper or slot wedges;
② Wear of bearings or foreign objects such as sand particles in the oil;
③ Loose iron core of stator and rotor;
④ Lack of oil in bearings;
⑤ Filling the air duct or wiping the fan cover;
⑥ Friction between the stator and rotor iron cores;
⑦ High or unbalanced power supply voltage;
⑧ Misconnection or short circuit of stator winding.
2. Troubleshooting
① Trim insulation and lower groove wedges;
② Replace bearings or clean bearings;
③ Repair the stator and rotor iron cores;
④ Cheer up;
⑤ Clean the air duct; Reinstall the device;
⑥ Eliminate scratches and, if necessary, small rotors inside the vehicle;
⑦ Check and adjust the power supply voltage;
⑧ Eliminate stator winding faults.
2, Excessive vibration during motor operation
1. Cause of malfunction
① Due to excessive clearance between worn bearings;
② Uneven air gap;
③ Unbalanced rotor;
④ Bending of the shaft;
⑤ Deformation or loosening of the iron core;
⑥ The center of the coupling (pulley) is not calibrated;
⑦ Fan imbalance;
⑧ Insufficient strength of the casing or foundation;
⑨ Loose motor foundation screws;
⑩ Open welding circuit of cage rotor; Open circuit of wound rotor; Fault in stator winding.
2. Troubleshooting
① Repair bearings and replace them if necessary;
② Adjust the air gap to make it even;
③ Correct rotor dynamic balance;
④ Straighten the shaft;
⑤ Correct overlapping iron cores;
⑥ Recalibrate to comply with regulations;
⑦ Repair the fan, correct balance, and correct its geometric shape;
⑧ Reinforce;
⑨ Tighten the foundation screws;
⑩ Repair the rotor winding; Repair the stator winding.
3, After being powered on, the motor cannot rotate, but there is no abnormal noise, odor, or smoke
1. Cause of malfunction
① Power supply not connected (at least two phases not connected);
② The fuse is blown (at least two phases are blown);
③ The overcurrent relay is set too small;
④ Control device wiring error.
2. Troubleshooting
① Check if there are any broken points at the power circuit switch, fuse, and junction box, and repair them;
② Check the fuse model, cause of melting, and replace it with a new fuse;
③ Adjust the relay setting value to match with the motor;
④ Correct wiring.
4, After being powered on, the motor does not rotate and the fuse burns out
1. Cause of malfunction
① One phase power supply is missing, or the fixed dry coil is connected in the opposite direction;
② Short circuit between stator windings;
③ Grounding of stator winding;
④ Stator winding wiring error;
⑤ The cross-section of the fuse is too small;
⑥ Short circuit or grounding of power line.
2. Troubleshooting
① Check if one phase of the knife switch is not properly closed, or if one phase of the power circuit is disconnected; Eliminate reverse connection faults;
② Identify the short circuit point and repair it;
③ Eliminate grounding;
④ Identify and correct incorrect connections;
⑤ Replace the fuse;
⑥ Eliminate grounding points.
5, There is a buzzing sound when the motor does not rotate after being powered on
1. Cause of malfunction
① Open circuit in stator and rotor windings (one phase disconnected) or loss of power in one phase of the power supply;
② Wrong connection at the beginning and end of the winding lead or reversed connection inside the winding;
③ Loose power circuit contacts with high contact resistance;
④ Excessive motor load or rotor jamming;
⑤ The power supply voltage is too low;
⑥ Small electric motors are assembled too tightly or the grease inside the bearings is too hard;
⑦ The bearing is stuck.
2. Troubleshooting
① Identify breakpoints and repair them;
② Check the polarity of the winding; Determine whether the end of the winding is correct;
③ Tighten the loose wiring screws, use a multimeter to check if each joint is false, and repair it;
④ Reduce load or detect and eliminate mechanical faults;
⑤ The inspection is still in accordance with the regulations Δ The connection method was mistakenly connected as Y; Is the voltage drop too high due to the power supply wire being too thin, and should it be corrected;
⑥ Reassemble to make it flexible; Replace with qualified grease;
⑦ Repair the bearings.
6, The no-load current of the motor is unbalanced, and there is a large difference among the three items
1. Cause of malfunction
① When rewinding, the number of turns in the stator three-phase winding is not equal;
② Wrong connection of winding ends;
③ Power supply voltage imbalance;
④ The winding has faults such as inter turn short circuit and coil reverse connection.
2. Troubleshooting
① Rewind the stator winding;
② Check and correct;
③ Measure the power supply voltage and try to eliminate imbalance;
④ Quenching winding fault.
7, When the motor is unloaded or overloaded, the ammeter pointer becomes unstable and swings
1. Cause of malfunction
① Welding or breakage of cage rotor guide bars;
② Winding rotor fault (one phase open circuit) or poor contact of brush and collector ring short circuit device.
2. Troubleshooting
① Identify broken bars and repair or replace rotors;
② Check the rotor winding circuit and repair it.
8, The no-load current of the motor is balanced, but the value is large
1. Cause of malfunction
① When repairing, the number of turns in the stator winding is reduced too much;
② The power supply voltage is too high;
③ The Y-connected motor was mistakenly connected as Δ;
④ During motor assembly, the rotor is reversed, causing the stator core to be misaligned and reducing the effective length;
⑤ Excessive or uneven air gap;
⑥ Improper use of hot dismantling method during major overhaul and dismantling of old windings resulted in burning of the iron core.
2. Troubleshooting
① Rewind the stator winding and restore the correct number of turns;
② Try to restore the rated voltage;
③ Change to Y;
④ Reassemble;
⑤ Replace the new rotor or adjust the air gap;
⑥ Repair the iron core or recalculate the winding, and increase the number of turns appropriately.
9, The motor is difficult to start, and at rated load, the speed is significantly lower than the rated speed
1. Cause of malfunction
① The power supply voltage is too low;
② Δ The motor is mistakenly connected to Y;
③ Welding or fracture of cage rotor;
④ Wrong or reversed connection of local coils in the stator and rotor;
⑤ Excessive increase in turns when repairing motor windings;
⑥ Motor overload.
2. Troubleshooting
① Measure the power supply voltage and try to improve it;
② Correct the connection method;
③ Check for open welds and breakpoints and repair them;
④ Identify and correct any misconnections;
⑤ Restore the correct number of turns;
⑥ Reduce load.
10, Electric motor overheating or even smoking
1. Cause of malfunction
① Excessive power supply voltage greatly increases the heating of the iron core;
② If the power supply voltage is too low and the motor is running under rated load, excessive current will cause the winding to heat up;
③ Improper use of hot dismantling method when repairing and dismantling windings can burn the iron core;
④ Friction between the stator and rotor iron cores;
⑤ Motor overload or frequent starting;
⑥ Cage rotor broken bars;
⑦ Motor phase loss, two-phase operation;
⑧ Insufficient impregnation of the fixed winding after rewinding;
⑨ The surface of the electric motor is dirty or the ventilation duct is blocked due to high ambient temperature;
⑩ Motor fan malfunction, poor ventilation; Fault in stator winding (short circuit between phases and turns; internal connection error in stator winding).
2. Troubleshooting
① Reduce the power supply voltage (such as adjusting the tap of the power transformer), if motor Y Δ If the connection is caused by an error, the connection should be corrected;
② Increase the power supply voltage or replace the thick power supply wire;
③ Repair the iron core and eliminate faults;
④ Eliminating friction points (adjusting air gaps or bumping the rotor);
⑤ Load reduction; Control starting according to the specified number of times;
⑥ Check and eliminate rotor winding faults;
⑦ Restore three-phase operation;
⑧ Adopting secondary impregnation and vacuum impregnation processes;
⑨ Clean the motor, improve the ambient temperature, and adopt cooling measures;
⑩ Check and repair the fan, replace it if necessary; Repair the stator winding and eliminate the fault.
11, Overheating of motor bearings
1. Cause of malfunction
① Excessive or insufficient lubricating grease;
② Poor oil quality with impurities;
③ Improper fit of bearings with journals or end caps (too loose or too tight)
④ Eccentricity of the bearing inner hole, rubbing against the shaft;
⑤ The motor end cover or bearing cover is not installed flat;
⑥ The coupling between the motor and the load is not calibrated, or the belt is too tight;
⑦ Excessive or insufficient bearing clearance;
⑧ The motor shaft is bent.
2. Troubleshooting
① Add lubricating grease according to regulations (1/3-2/3 of the volume);
② Replace clean lubricating grease;
③ If it is too loose, it can be repaired with adhesive. If it is too tight, apply it to the car and grind the inner hole of the shaft neck or end cover to make it suitable;
④ Repair the bearing cover and eliminate friction points;
⑤ Reassemble;
⑥ Recalibrate and adjust the belt tension;
⑦ Replace with new bearings;
⑧ Correct the motor shaft or replace the rotor.
