Typical Stop Loss Case of Brushless Motor
Feb 6, 2019
  • Brushless DC motor is composed of motor main body and actuator. It is a typical electromechanical integration product. Since the BLDCM operates in an automatic manner, it will not add a starting winding to the rotor like the synchronous motor starting under heavy load under frequency conversion speed regulation, nor will it oscillate and out of step when the load changes suddenly. Nowadays, rare earth Nd-Fe-B (Nd-Fe-B) materials with high magnetic energy product are widely used as permanent magnets for medium and small capacity brushless DC motors. Therefore, the volume of the rare earth permanent magnet brushless motor is smaller than that of the same capacity three-phase asynchronous motor by one base number.

  • Brushless DC motor is widely used, but after a long period of operation, various faults will occur. It is an important work to judge the cause of the fault and deal with it in time to prevent the fault from expanding and ensure the normal operation of the equipment.

The main failures and analysis are as follows:

I. motor encoder alarm

1. Cause of failure

Wiring error;

Electromagnetic interference;

3. Hardware damage caused by mechanical vibration.

(4) pollution caused by environmental pollution;

2. Troubleshooting

Check wiring and eliminate errors;

(2) Check whether the shield is in place, check whether the wiring is reasonable and solve, if necessary add filter to improve;

Check mechanical structure and improve it;

Check whether the encoders are polluted or corroded (dust, oil dirt, etc.), and strengthen the protection.

3. Installation and wiring standards

(1) use the original cable as far as possible.

(2) separate cables from them as far as possible, especially high pollution wiring.

(3) use internal power as much as possible. If switching power is used, the filter should be used to ensure that the power reaches the cleanliness level.

(4) always connect the public to the ground;

The encoder housing is insulated from the machine structure and connected to the cable shielding layer.

If the encoder can not be insulated, the cable shield layer can be connected to the encoder housing and drive frame grounding (or dedicated terminals).

Two. Broken shaft of motor

1. Cause of failure

(1) unreasonable mechanical design results in excessive radial load.

(2) dead ends or severe transient overload.

3. The motor and reducer are not concentric when assembling.

2. Troubleshooting

(1) check the large radial load capacity of motor samples and improve the mechanical design.

Second, check the operation of the load side, confirm the actual process requirements and improve it.

Check whether the load is stable, whether there is vibration, and improve the accuracy of mechanical assembly.

Three. No load current of motor, unbalanced three-phase.

1. Cause of failure

The winding ends of the winding are wrong.

2. Unbalanced supply voltage;

3. Windings exist inter turn short circuit and coil reverse connection.

2. Troubleshooting

First, check and correct.

Second, measure the power supply voltage and try to eliminate the imbalance.

Eliminate winding fault.

Four. When the motor is running, the noise is abnormal.

1. Cause of failure

(1) bearing wear or foreign particles in oil.

(2) loose core of rotor;

3. Bearing is short of oil.

(4) the supply voltage is too high or unbalanced.

2. Troubleshooting

Replacing bearings or cleaning bearings;

2. Overhaul rotor core;

(3) refueling;

Check and adjust the supply voltage.

Five. The motor is difficult to start. When the load is rated, the speed of the motor is lower than the rated speed.

1. Cause of failure

(1) the power supply voltage is too low.

Secondly, the motor is misconnected by face connection.

3. The rotor is welded or broken.

4. The local coil of the rotor is wrongly connected and reversed.

(3) increasing the number of turns when repairing motor windings;

Motor overload.

2. Troubleshooting

First, measure the power supply voltage and try to improve it.

Second, correct the connection.

Check welding and breakage and repair.

(4) correct the wrong connection.

Correct the number of turns;

Six. The motor can not rotate after electrifying, but it does not smell loudly, nor does it smell and smoke.

1. Cause of failure

(1) the power is not connected (at least two phases fail).

Fuse fuses (at least two phases).

The overcurrent relay is too small.

4. Wrong wiring of control equipment.

2. Troubleshooting

Check whether there is breakpoint in the power circuit switch, fuse and junction box, and repair.

Second, check the fuse type and fuse causes, replace the new fuse.

Adjust the relay setting value to match the motor.

3. Correct wiring.

Seven. The motor vibrates in operation.

1. Cause of failure

Due to excessive wear bearing clearance;

(2) the air gap is uneven.

3. Rotor imbalance;

(4) bending of the rotating shaft;

(5) the coaxality of the coupling (belt pulley) is too low.

2. Troubleshooting

First, repair the bearing and replace it when necessary.

Second, adjust the air gap to make it uniform.

3. Correct rotor dynamic balance.

Straightening the shaft;

(5) recalibrate to make it conform to the regulations.

Eight. The motor does not turn to buzz after power on.

1. Cause of failure

(1) the rotor winding has a circuit breaker (one phase disconnection) or a power loss in one phase.

2. The winding end of the winding lead is connected to the wrong end or the inner side of the winding is reversed.

(3) the contact point of the power circuit is loose, and the contact resistance is large.

(4) motor load is too large or rotor is jammed.

The power supply voltage is too low.

Small motor assembly is too tight or grease in bearings is excellent.

The bearing is jammed.

2. Troubleshooting

First, check the broken points to repair.

Check the polarity of the winding; judge whether the end of the winding is correct.

Tighten loose connection screws and use multimeter to determine whether the joints are false or not.

Reduce load or detect and eliminate mechanical failure.

_Check whether the prescribed surface connection is incorrectly connected; if the voltage drop is too large due to too fine power conductor, correct it.

Reassembly to make it flexible; replace qualified oils and fats;

Repair bearings.

Nine. Bearing Overheating

1. Cause of failure

(1) too much or too little grease.

(2) oil is not good enough to contain impurities.

3. Improper alignment of bearing and journal or end cover (loose or too tight);

The inner hole of the bearing is eccentrically and rubbed with the shaft.

(5) the motor end cover or bearing cover is not levelled.

The coupling between the motor and the load is not corrected or the belt is too tight.

The bearing clearance is too large or too small.

The motor shaft is bent.

2. troubleshooting

1. Grease (volume 1/3-2/3) according to regulations.

Replace clean lubricating grease.

(3) too loose can be repaired with adhesive, too tight to the car, grinding the neck or end cover hole to make it suitable.

Fourth, repair the bearing cover, eliminate the rub point; pay more attention to the training of micro signal technology.


Re adjust and adjust belt tension;

Replacement of new bearings;

Correct the motor shaft or replace the rotor.

Ten. Motor overheating or even smoking

1. Cause of failure

(1) the power supply voltage is too high.

2. The power supply voltage is too low, and the motor runs with rated load.

(3) when repairing and removing the winding, the thermal disassembly method is improper and the burn iron core is used.

(4) motor overload or frequent start;

The motor is short of phase and runs in two phases.

After winding, it is not enough to paint the winding.

The environment temperature is high, the surface of the motor is much dirty, or the ventilation channel is blocked.

2. Troubleshooting

(1) reduce the power supply voltage (for example, adjust the tap changer of the power transformer);

(2) increasing the supply voltage or changing the power supply wire;

3. Troubleshooting iron core;

Reduce load; control starting according to prescribed times.

Restore three phase operation;

Two times of dipping and vacuum dipping process.

Cleaning motor, improving environment temperature and adopting cooling measures.

Analysis of ten typical damage causes of servo motors

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