What are the reasons why the servo motor cannot rotate?

Three-phase AC servo motors are widely used, but after long-term operation, various faults may occur. Timely identifying the cause of servo motor faults and taking corresponding measures is an important task to prevent the expansion of faults and ensure the normal operation of equipment.

1、 After being powered on, the servo motor cannot rotate, but there is no abnormal noise, odor, or smoke.

1. Fault cause

① The power supply is not connected (at least two phases are not connected); ② Fuse blown (at least two phase blown); ③ The overcurrent relay is too small; ④ Control device wiring error.

2. Troubleshooting

① Check the power circuit switch, fuse, and junction box for any broken points and repair them; ② Check the model and cause of the fuse, and replace it with a new one; ③ Adjust the relay setting value to cooperate with the motor; ④ Correct wiring.

2、 There is a buzzing sound when the servo motor does not rotate after being powered on

1. Fault cause

① There is an open circuit in the rotor winding (one phase disconnection) or a loss of power in one phase of the power supply; ② The beginning and end of the winding lead are connected incorrectly or the winding is internally connected in reverse; ③ Loose power circuit contacts with high contact resistance; ④ The motor is overloaded or the rotor is stuck; 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 the 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 determine if each connector is false, and repair it; ④ Reduce load or detect and eliminate mechanical faults, ⑤ check whether the specified surface connection method is mistakenly connected; Whether the voltage drop is too large due to the thin power wire, correct it, and ⑥ reassemble it to make it flexible; Replace with qualified grease; ⑦ Repair the bearings.

3、 It is difficult to start the servo motor, 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 Misconnection of surface connection method motor; ③ Welding or fracture of the rotor; ④ Misconnection or reverse connection of local coils of the rotor; ⑤ Excessive increase in turns when repairing the motor winding; ⑥ motor overload 

2. Troubleshooting

① Measure the power supply voltage and try to improve it; ② Correction 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 Load shedding.

4、 The no-load current of the servo motor is unbalanced, with a large three-phase difference

1. Fault cause

① Winding end to end connection error; ② Unbalanced power supply voltage; ③ The winding has faults such as inter turn short circuit and coil reversal.

2. Troubleshooting

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

5、 Abnormal sound or abnormal noise when the servo motor is running

1. Fault cause

① Bearing wear or foreign objects such as sand particles in the oil; ② Loose rotor core; ③ Lack of oil in bearings; ④ The power supply voltage is too high or unbalanced.

2. Troubleshooting

① Replace or clean bearings; ② Maintain the rotor iron core; ③ Refuel; ④ Check and adjust the power supply voltage.

6、 The servo motor vibrates significantly during operation

1. Fault cause

① Excessive bearing clearance due to wear; ② Uneven air gap; ③ Unbalanced rotor; ④ Bending of the shaft; ⑤ The coaxiality of the coupling (pulley) is too low.

2. Troubleshooting

① Maintain bearings and replace them if necessary; ② Adjust the air gap to make it even; ③ Correct the dynamic balance of the rotor; ④ Straighten the rotating shaft; ⑤ Recalibrate to ensure compliance with regulations.

7、 Servo motor bearing overheating

1. Fault cause

① Excessive or insufficient grease; ② Poor oil quality with impurities; ③ Improper fit of bearings with journals or end caps (too loose or too 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 Excessive or small 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 with clean lubricating grease; ③ If it is too loose, it can be repaired with adhesive. If it is too tight, apply it to the vehicle and grind the inner hole of the journal 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 a new bearing; ⑧ Correct the motor shaft or replace the rotor.

8、 Servo motor overheats or even smokes

1. Fault cause

① The power supply voltage is too high; ② If the power supply voltage is too low and the motor is running with rated load, excessive current will cause the winding to heat up; ③ Improper use of hot disassembly method when repairing and dismantling windings can burn the iron core; ④ Motor overload or frequent starting; ⑤ Motor phase loss, two-phase operation; ⑥ Insufficient impregnation of the fixed winding after rewinding; ⑦ The surface of the motor may have excessive dirt or blocked ventilation ducts due to high ambient temperature.

2. Troubleshooting

① Reduce the power supply voltage (such as adjusting the tap of the power transformer); ② Increase the power supply voltage or replace the thick power supply wire; ③ Repair the iron core and eliminate faults; ④ Load shedding; Control starting according to the specified number of times; ⑤ Restore three-phase operation;