Analysis and treatment of common faults of the hot

2022-08-20
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Analysis and treatment of common faults of three-phase asynchronous motors

three phase asynchronous motors are widely used, but after long-term operation, various faults will occur. Timely judging the cause of the fault and handling it accordingly is an important work to prevent the expansion of the fault and ensure the normal operation of the equipment

I. the motor cannot rotate after being powered on, but there is no abnormal sound, odor and smoke

1. fault cause ① power supply is not connected (at least two phases are not connected); ② Fuse fusing (at least two phases fusing); ③ The overcurrent relay is adjusted too small; ④ Wrong wiring of control equipment

2. Troubleshooting ① check whether there are breakpoints at the power circuit switch, fuse and junction box, and repair them; ② Check the fuse model and cause, and replace the fuse; ③ Adjust the setting value of the relay to match the motor; ④ Correct the wiring

II. The motor does not rotate after being powered on, and then the fuse burns out

1. Fault cause ① lack of one phase power supply, or the fixed dry coil is connected in the opposite direction; ② Phase to phase short circuit of stator winding; ③ Stator winding grounding; ④ Stator winding wiring error; ⑤ The fuse section is too small; ⑤ The power line is short circuited or grounded

2. Troubleshooting ① check whether one phase of the knife switch is not closed well, but one phase of the power circuit is disconnected; Eliminate reverse connection fault; ② Find out the short-circuit point and repair it; ③ Eliminate grounding; ④ Find out the wrong connection and correct it; ⑤ Replace the fuse; ③ Eliminate the grounding point

III. the motor does not rotate after being powered on, and there is a buzzing sound

l. cause of fault ① stator and rotor windings have open circuit (one phase is disconnected) or one phase of the power supply loses power; ② The beginning and end of the winding outgoing line are connected incorrectly or the internal connection of the winding is reversed; ③ The contact of power circuit is loose and the contact resistance is large; ④ The motor load is too large or the rotor is stuck; ⑤ The power supply voltage is too low; ⑥ The assembly of small motors is too tight or the grease in the bearings is too hard; ⑦ The bearing is stuck

2. Troubleshooting ① find out the breaking point and repair it; ② Check the polarity of the winding; Judge whether the end of the winding is correct and the performance has no change compared with that of poly4 fluoroethylene; ③ Tighten the loose wiring screws, use a multimeter to judge whether each joint is false, and repair it; ④ Reduce the load or find out and eliminate mechanical faults, ⑤ check whether the specified surface connection method is wrongly connected to y; Whether the voltage drop is too large due to the too thin power conductor, correct it, ⑥ reassemble it to make it flexible; Replace qualified grease; ⑦ Repair the bearing

IV. the motor is difficult to start, and the motor speed is much lower than the rated speed at rated load

1. Fault cause ① the power supply voltage is too low; ② The motor of face connection method is wrongly connected as y; ③ Open welding or fracture of cage rotor; ④ Local coils of stator and rotor are wrongly connected and inversely connected; ③ Too many turns are added when repairing the motor winding; ⑤ The motor is overloaded

2. Troubleshooting ① measure the power supply voltage and try to improve it; ② Correct the connection method; ③ Check open welding and breakpoints and repair them; ④ Find out the wrong connection and correct it; ⑤ Restore the correct number of turns; ⑥ Load shedding

v. the no-load current of the motor is unbalanced, and the three-phase difference is large

1. Fault cause ① when rewinding, the turns of the three-phase windings of the stator are not equal; ② Wrong connection of winding ends; ③ Unbalanced power supply voltage; ④ There are faults such as inter turn short circuit and coil reverse connection in the winding

2. Troubleshooting ① rewind the stator winding; ② Check and correct; ③ Measure the power supply voltage and try to eliminate the imbalance; ④ Clear the winding fault

VI. when the motor is unloaded and overloaded, the ammeter pointer is unstable and swings

1. Fault cause ① the cage rotor guide bar is disconnected or broken; ② Winding rotor fault (one phase open circuit) or poor contact of brush and collector ring short circuit device

2. Troubleshooting ① find out the broken bar and repair it or replace the rotor; ② Check the circuit around the rotor and repair it

VII. The no-load current of the motor is balanced, but the value is large

1. Fault cause ① when repairing, the number of turns of the stator winding is reduced too much; ② The power supply voltage is too high; ③ Y is connected to the motor by mistake; ④ During motor assembly, the rotor is installed reversely, so that the stator core is not aligned and the effective length is shortened; ⑤ The air gap is too large or uneven; ⑥ When removing the old winding during overhaul, the iron core was burnt due to improper use of thermal disassembly method

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; ③ Replace the rotor or adjust the air gap; ⑤ Repair the iron core or recalculate the winding, and appropriately increase the number of turns

VIII. The noise of the motor is abnormal during operation, with abnormal noise

1. Fault cause ① the rotor rubs against the stator insulating paper or slot wedge; ② Bearing wear or foreign matters such as sand in oil; ③ The stator and rotor iron core is loose; ④ The bearing is short of oil; ⑤ Fill the air duct or wipe the fan hood, ⑥ rub the stator and rotor iron cores; ⑦ The power supply voltage is too high or unbalanced; ⑧ The stator winding is wrongly connected or short circuited

2. so it is called conditional yield strength or yield strength for short σ 0.2 troubleshooting ① trim the insulation and cut down the slot wedge; ② Replace the bearing or clean the bearing; ③ Repair stator and rotor iron cores; ④ Refuel; ⑤ Clean the air duct; Reinstall the device; ⑥ Eliminate scratches, and if necessary, the small rotor in the car; ⑦ Check and adjust the power supply voltage; ⑧ Eliminate stator winding fault

IX. the motor vibrates greatly during operation

1. Cause of fault ① excessive bearing clearance due to wear; ② Uneven air gap; ③ The rotor is unbalanced; ④ The rotating shaft is bent; ⑤ Deformation or looseness of iron core; ⑥ The coupling (pulley) center is not corrected; ⑦ The fan is unbalanced; ⑧ Insufficient strength of casing or foundation; ⑨ The anchor screw of the motor is loose; ⑩ Open welding and open circuit of cage rotor; The wound rotor is open circuit; Add stator winding fault

2. Troubleshooting ① repair the bearing and replace it if necessary; ② Adjust the air gap to make it even; ③ Correct the rotor dynamic balance; ④ Straighten the rotating shaft; ⑤ Correct the overlapping iron core, ⑥ recalibrate it to make it meet the requirements; ⑦ Repair the fan, correct the balance and correct its geometry; ⑧ Reinforce; ⑨ Tighten the anchor screws; ⑩ Repair the rotor winding; Repair the stator winding

X. Bearing Overheating

1. Fault cause ① too much or too little grease; ② Poor oil quality with impurities; ③ The bearing is improperly matched with the journal or end cover (too loose or tight); ④ The inner hole of the bearing is eccentric and rubs 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 The bearing clearance is too large or too small; ⑧ The motor shaft is bent

2. Troubleshooting ① add grease as required (1//3 of volume); ② Replace the clean lubricating grease; ③ If it is too loose, it can be repaired with adhesive, and if it is too tight, the axle journal or the inner hole of the end cover can be ground to make it suitable; ④ Repair the bearing cover and eliminate the rubbing points; ⑤ Reassemble; ⑥ Recalibrate and adjust the belt tension; ⑦ Replace with new bearings; ⑧ Correct the motor shaft or replace the rotor

Xi. The motor is overheated and even smokes

1. Fault cause ① the power supply voltage is too high, which greatly increases the heating of the iron core; ② The power supply voltage is too low, the motor operates with rated load, and excessive current will cause the winding to heat up; ③ When repairing and removing the winding, the improper hot disassembly method will burn the iron core; ④ The stator and rotor cores rub against each other; ⑤ The cheaper the motor is, the better. Overload or frequent starting; ⑥ Broken bars of cage rotor; ⑦ The motor is out of phase and operates in two phases; ⑧ After rewinding, the winding is not fully impregnated; ⑨ High ambient temperature, more dirt on the motor surface, or blocked ventilation duct; ⑩ Motor fan failure, poor ventilation; Stator winding fault (phase to phase, turn to turn short circuit; internal connection error of stator winding)

2. Troubleshooting ① reduce the power supply voltage (such as adjusting the tap of the power supply transformer). If it is caused by the wrong connection method of the motor Y, it should be corrected that chitin is the only natural high molecular polymer method with positive charge in nature; ② Increase the power supply voltage or change the thick power supply wire; ③ Repair the iron core and eliminate faults; ④ Eliminate the rubbing points (adjust the air gap or bump, turn the rotor); ⑤ Load shedding; Control the starting according to the specified number of times; ⑥ Check and eliminate rotor winding faults; ⑦ Restore three-phase operation; ⑧ Adopt the technology of twice dipping paint and vacuum dipping paint; ⑨ Clean the motor, improve the ambient temperature, and take cooling measures; ⑩ Check and repair the fan, and replace it if necessary; Repair the stator winding and eliminate the fault

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