Analysis of the causes of AC servo motor damage

Three-phase AC servo motors are widely used, but various faults may occur after long-term operation. Timely judgment of the cause of the fault and appropriate handling are important to prevent the expansion of the fault and ensure the normal operation of the equipment.

I. The motor does not rotate after power-on, but there is no abnormal sound, smell, or smoke.

1. Fault causes: ① Power supply not connected (at least two phases not connected); ② Fuse blown (at least two phases blown); ③ Overcurrent relay set too small; ④ Control equipment wiring error.

2. Troubleshooting: ① Check the power circuit switch, fuse, and junction box for disconnections and repair; ② Check the fuse model and cause of failure, replace the fuse; ③ Adjust the relay setting value to match the motor; ④ Correct the wiring.

II. The motor does not rotate after power-on, but there is a humming sound.

1. Fault causes: ① Open circuit in the rotor winding (one phase disconnected) or one phase of the power supply is lost; ② Incorrect connection of the winding leads or reversed winding inside; ③ Loose contact in the power circuit, high contact resistance; ④ Excessive motor load or rotor jamming; ⑤ Too low power supply voltage; ⑥ Too tight assembly of small motor or too hard grease in the bearing; ⑦ Bearing jammed.

2. Troubleshooting: ① Identify and repair the break; ② Check the winding polarity; determine if the winding ends are correct; ③ Tighten loose wiring screws, use a multimeter to determine if any joints are falsely connected, and repair; ④ Reduce the load or find and eliminate mechanical faults; ⑤ Check if the specified connection method is incorrectly connected; whether the voltage drop is too large due to the thin power cord, correct it; ⑥ Reassemble to make it flexible; replace qualified grease

⑦ Repair the bearings.

III. The motor starts with difficulty, and the motor speed is much lower than the rated speed under rated load.

1. Fault causes: ① Too low power supply voltage; ② Incorrect motor connection method; ③ Rotor open welding or fracture; ④ Partial rotor coil misconnected or reversed; ⑤ Too many turns added during motor winding repair; 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 breaks and repair; ④ Find the misconnected part and correct it; ⑤ Restore the correct number of turns; ⑥ Reduce the load.

IV. The no-load current of the motor is unbalanced, and the three phases have a large difference.

1. Fault causes: ① Incorrect connection of the winding ends; ② Unbalanced power supply voltage; ③ Turn-to-turn short circuit, coil reversal, etc., in the winding.

2. Troubleshooting: ① Check and correct; ② Measure the power supply voltage and try to eliminate the imbalance; ③ Eliminate the winding fault.

V. Abnormal noise during motor operation

Fault causes: ① Bearing wear or foreign matter such as sand grains in the oil; ② Loose rotor core; ③ Lack of oil in the bearing; ④ Too high or unbalanced power supply voltage.

Troubleshooting: ① Replace or clean the bearing; ② Repair the rotor core; ③ Add oil; ④ Check and adjust the power supply voltage.

VI. Excessive vibration during motor operation

Fault causes: ① Excessive bearing clearance due to wear; ② Uneven air gap; ③ Rotor imbalance; ④ Bent shaft; ⑤ Low coaxiality of coupling (pulley).

Troubleshooting: ① Repair the bearings and replace them if necessary; ② Adjust the air gap to make it uniform; ③ Correct the rotor dynamic balance; ④ Straighten the shaft; ⑤ Recalibrate to meet the specifications.

VII. Overheating of the bearing

1. Fault causes: ① Too much or too little grease; ② Poor oil quality containing impurities; ③ Improper fit between bearing and journal or end cover (too loose or too tight); ④ Eccentric bearing bore, rubbing against the shaft; ⑤ Motor end cover or bearing cover not installed flat; ⑥ Coupling between motor and load not calibrated, or belt too tight; ⑦ Too large or too small bearing clearance; ⑧ Bent motor shaft.

2. Troubleshooting: ① Add lubricating grease according to regulations (1/3-2/3 of the volume); ② Replace clean lubricating grease; ③ If too loose, use adhesive to repair, if too tight, machine the journal or end cover bore to make it suitable; ④ Repair the bearing cover to eliminate rubbing points; ⑤ Reassemble; ⑥ Recalibrate and adjust belt tension; ⑦ Replace new bearings; ⑧ Correct the motor shaft or replace the rotor.

VIII. Motor overheating and even smoking

Fault causes: ① Too high power supply voltage; ② Too low power supply voltage, the motor runs with rated load, and the excessive current causes the winding to overheat; ③ Improper use of hot removal method when repairing and removing the winding, burning the iron core; ④ Motor overload or frequent starting; ⑤ Motor missing phase, two-phase operation; ⑥ Insufficient impregnation of stator winding after rewinding; ⑦ High ambient temperature, many surface contaminants on the motor, or blocked ventilation duct;

Troubleshooting: ① Reduce the power supply voltage (e.g., adjust the tap of the power transformer); ② Increase the power supply voltage or replace the thicker power cord; ③ Repair the iron core and eliminate the fault; ④ Reduce the load; control the number of starts according to the regulations; ⑤ Restore three-phase operation; ⑥ Use secondary impregnation and vacuum impregnation technology; ⑦ Clean the motor, improve the ambient temperature, and adopt cooling measures;