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Servo motor ten fault analysis, after reading you are also an expert!

Three-phase AC servo motors are widely used, but after long-term operation, various failures will occur. To determine the cause of the failure in time and deal with it accordingly is an important task to prevent the expansion of the failure and ensure the normal operation of the equipment.


Ⅰ. Motor encoder alarm

1. Reasons for failure

①Wiring error;

②Electromagnetic interference;

③Encoder hardware damage caused by mechanical vibration;

④Pollution caused by the on-site environment;

2, troubleshooting

①Check the wiring and eliminate errors;

②Check whether the shielding is in place, check whether the wiring is reasonable and solve it, if necessary, add a filter to improve it;

③Check the mechanical structure and improve it;

④Check whether the inside of the encoder is polluted or corroded (dust, oil, etc.), and strengthen protection;

3. Installation and wiring standards

①Try to use the original cable;

②Separate the cable to keep it away from the contaminated wiring as far as possible, especially the highly contaminated wiring;

③Always use the internal power supply as much as possible. If you use a switching power supply, you should use a filter to ensure that the power supply reaches the cleanliness level;

④ Always ground the common terminal;

⑤Keep the encoder shell insulated from the machine structure and connect it to the cable shielding layer;

⑥If the encoder cannot be insulated, the cable shield can be connected to the ground (or dedicated terminal) on the encoder housing and the drive frame.


Ⅱ. Motor shaft broken

1. Reasons for failure

①Unreasonable mechanical design leads to excessive radial load force;

②The load end is stuck or is severely overloaded;

③When assembling the motor and the reducer, they are not concentric.

2, troubleshooting

①Check the maximum radial load force that the motor sample can bear, and improve the mechanical design;

②Check the operation of the load side, confirm the actual process requirements and make improvements;

③Check whether the load is running stably, whether there is vibration, and improve the accuracy of mechanical assembly.


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

1. Reasons for failure

①The winding ends are connected wrongly;

②The power supply voltage is unbalanced;

③The winding has faults such as short circuit between turns and reverse coil connection. 

2, troubleshooting

①Check and correct;

②Measure the power supply voltage and try to eliminate the imbalance;

③ Eliminate winding faults.


Ⅳ. When the motor is running, the noise is abnormal and there are abnormal noises

1. Reasons for failure

①Bearing wear or foreign matter such as sand particles in the oil;

②The rotor core is loose;

③The bearing is short of oil;

④The power supply voltage is too high or unbalanced.  

2, troubleshooting

①Replace the bearing or clean the bearing;

②Overhaul the rotor core;

③Come on;

④Check and adjust the power supply voltage


Ⅴ. It is difficult to start the motor. When the rated load, the motor speed is much lower than the rated speed

1. Reasons for failure

①The power supply voltage is too low;

②Wrong connection of the surface connection method;

③The rotor is welded or broken;

④Wrong connection or reverse connection of the rotor local coil;

③To increase the number of turns when repairing the motor windings;

⑤The motor is overloaded.

2, troubleshooting

①Measure the power supply voltage and try to improve;

②Correct the connection method;

③Check and repair open soldering and breakpoints;

④Identify the wrong connection and correct it;

⑤Restore the correct number of turns;

⑥ Load reduction.


Ⅵ. The motor can't rotate after power on, but there is no abnormal noise, no strange smell and smoke?

1. Reasons for failure

①The power supply is not connected (at least two phases are not connected);

②The fuse is blown (at least two phases are blown);

③The overcurrent relay is adjusted too small;

④The wiring of the control equipment is wrong.

2, troubleshooting

①Check whether there are breakpoints at the power circuit switch, fuse, and junction box, and repair it;

②Check the fuse type, the cause of fusing, and replace it with a new one;

③Adjust the setting value of the relay to cooperate with the motor;

④ Correct the wiring.


Ⅶ. The motor vibrates greatly during operation

1. Reasons for failure

①The bearing clearance is too large due to wear;

②Uneven air gap;

③The rotor is unbalanced;

④The shaft is bent;

⑤The coaxiality of the coupling (pulley) is too low.

2, troubleshooting

①Check the bearing and replace if necessary;

②Adjust the air gap to make it uniform;

③Correct the rotor dynamic balance;

④Straighten the shaft;

⑤Recalibrate to make it meet the requirements.


Ⅷ. The motor does not rotate and there is a buzzing sound after power-on

1. Reasons for failure

①The rotor winding has an open circuit (one-phase disconnection) or one phase of the power supply loses power;

②The beginning and end of the winding lead wire is connected wrongly or the winding is connected reversely;

③The power circuit contacts are loose and the contact resistance is large;

④The motor load is too large or the rotor is stuck;

⑤The power supply voltage is too low;

⑥The small motor assembly is too tight or the grease in the bearing is too hard;

⑦The bearing is stuck.

2, troubleshooting

①Find the breakpoint and fix it;

②Check the polarity of the winding; determine whether the end of the winding is correct;

③Tighten the loose wiring screws, use a multimeter to judge whether each connector is falsely connected, and repair it;

④Reduce load or detect and eliminate mechanical failures;

⑤Check if the specified surface connection method is wrongly connected; if the voltage drop is too large due to the power wire is too thin, correct it;

⑥Reassemble to make it flexible; replace qualified grease;

⑦Repair the bearing.


Ⅸ. he bearing is overheated?

1. Reasons for failure

①Too much or too little grease;

②The oil quality is not good and contains impurities;

③Improper fit between bearing and journal or end cover (too loose or too tight);

④The inner bore of the bearing is eccentric and rubs against the shaft;

⑤The motor end cover or bearing cover is not installed flat;

⑥The coupling between the motor and the load is not calibrated, or the belt is too tight;

⑦The bearing clearance is too large or too small;

⑧The motor shaft is bent.

2, troubleshooting

①Add grease as required (1/3-2/3 of the volume);

②Replace clean grease;

③If it is too loose, it can be repaired with adhesive. If it is too tight, it can be used to grind the shaft journal or the inner hole of the end cover to make it fit;

④Repair the bearing cover to eliminate rubbing points;


⑥Recalibrate and adjust the belt tension;

⑦Replace with new bearings;

⑧ Correct the motor shaft or replace the rotor.


Ⅹ. The motor is overheated or even smoking?

1. Reasons for failure

①The power supply voltage is too high;

②The power supply voltage is too low, the motor is running with rated load, and the current is too high to cause the winding to heat up;

③When repairing and removing the windings, the hot disassembly method is improperly used, which will burn the iron core;

④The motor is overloaded or starts frequently;

⑤The motor is running in two phases due to lack of phase;

⑥After rewinding, it is determined that the winding paint is not sufficiently dipped;

⑦High ambient temperature, the surface of the motor is dirty, or the air duct is blocked.

2, troubleshooting

①Reduce the power supply voltage (such as adjusting the tap of the power supply transformer);

②Increase the power supply voltage or change a thicker power supply wire;

③Examine and repair the iron core and eliminate the fault;

④Reduce the load; control the start according to the specified number of times;

⑤Resume three-phase operation;

⑥Using secondary dipping and vacuum dipping process;

⑦Clean the motor, improve the ambient temperature, and adopt cooling measures.