9 Common Faults of Motor and the Troubleshooting Methods

The motor cannot be started.


1) The power supply is not connected;

2) Open circuit of winding;

3) Winding grounding or phase to phase short circuit;

4) Winding wiring error;

5) Melt burnout;

6) Wrong wiring of control equipment.


1) Check the switch, melt, each contact point and the outgoing wire head of the motor;

2) Heat the open circuit part to the temperature allowed by the insulation grade to soften the paint, then pick up the wire, repair the broken part with wires of the same specification, wrap the insulation, and then paint and dry;

3) The treatment method is the same as above, except that the grounding or short-circuit parts are padded with insulation, and then painted and dried;

4) Check the wiring diagram, heat the end and connect it again according to the correct connection method (including binding, insulation treatment and painting);

5) Find out the cause, eliminate the fault, and prepare new melt according to the motor specification;

6) Correct the wiring.

After the motor is pulled into the power supply, the melt is burnt off.


1) Single phase start;

2) The motor is overloaded or stuck;

3) The melt cross-sectional area is too small;

4) The connecting line between the power supply and the motor is short circuited.


1) Check the contact points of power line, motor outgoing line, fuse and switch, and repair after finding out the broken line or false connection fault;

2) Adjust the load to the rated value and eliminate the fault of the towed mechanism;

3) The melt does not protect the motor from overload.

Generally, the melt should be selected according to the following formula;

Melt rated current = starting current / (2 ~ 3);

4) Check the short circuit point and repair it.

The motor does not start and buzzes after being powered on.


1) The motor is stuck or overloaded;

2) The power supply fails to be fully connected;

3) The voltage is too low;

4) For small motors, the grease is hard or the assembly is too tight.


1) Check the equipment and eliminate faults;

2) Replace the fuse melt; Tighten the loose screws of the terminal;

Check the disconnection or false connection fault of the power line with a multimeter, and then repair it;

3) If the △ connection motor is wrongly connected to Y connection, it should be changed back to △  connection.

If the power supply voltage is too low, contact the power supply department for solution;

If the voltage drop of the power line is too large and the voltage is too low, the thick cable should be changed;

4) Select the appropriate grease to improve the assembly quality.

The motor housing is charged.


1) Wrong power line and grounding wire;

2) The motor winding is damp and the insulation is seriously aged;

3) The outgoing line is grounded with the junction box.


1) Correct errors;

2) The motor shall be dried and the aged insulation shall be renewed;

3) Wrap or update the insulation of outgoing line and repair the junction box.

It is difficult to start the motor. After adding the rated load, the motor speed is lower than the rated speed.


1) The power supply voltage is too low;

2) △ the connecting winding is wrongly connected into Y connection;

3) Open welding or fracture of cage rotor;

4) Too many turns during rewinding.


1) Check the input power voltage of the motor with a voltmeter or multimeter, and then deal with it;

2) Change the Y connection back to △ connection;

3) Repair after checking the open welding or fracture;

4) Rewind according to the correct number of winding turns.

Low insulation resistance


1) The winding is damp or wetted by water;

2) Winding insulation aging.


1) Heat and dry;

2) After identification, it can be used continuously, cleaned, dried and repainted;

If the insulation is aged and cannot operate safely, the insulation shall be replaced.

Abnormal noise during motor operation


1) The bearing is worn and faulty;

2) Loose stator and rotor iron core;

3) The voltage is too high or unbalanced;

4) The bearing lacks lubricating grease;

5) The fan touches the hood or the air duct is blocked;

6) The air gap is uneven and the stator and rotor rub against each other.


1) Repair or replace new bearings;

2) Check the cause of vibration and re compress the iron core for treatment;

3) Measure the power supply voltage, check the causes of high voltage and imbalance, and deal with them;

4) Clean the bearing and fill it with grease to make it full of 1 / 2 ~ 2 / 3 of the volume of the bearing chamber;

5) Repair the fan and hood to make them correct in size; Clean the ventilation duct;

6) Adjust the air gap to improve the assembly quality.

Motor overheating or smoking


1) The power supply voltage is too high, which makes the magnetic flux density of the iron core supersaturated, resulting in the rise of the motor temperature;

2) The power supply voltage is too low and the motor temperature rise is too high under rated load;

3) The stator and rotor iron cores rub against each other;

4) The motor is overloaded or the drag of production machinery is too large, causing the motor to heat up;

5) The motor starts frequently or has too many times of forward and reverse rotation;

6) Fan failure, poor ventilation.


1) If the power supply voltage exceeds the standard a lot, contact the power supply department for solution;

2) If it is caused by excessive voltage drop of the power line, the thicker power line can be replaced;

If the power supply voltage is too low, contact the power supply department to increase the power supply voltage;

3) Check the cause of the fault. If the bearing clearance exceeds the limit, replace the bearing;

If the rotating shaft is bent, it needs to be straightened;

When the iron core is loose or deformed, the iron core shall be handled to eliminate the fault;

4) Eliminate the fault of driving machinery and reduce the resistance;

According to the current instructions, if the rated current exceeds, reduce the load, replace the motor with large capacity or take capacity pulling measures;

5) Reduce the starting, forward and reverse rotation times of the motor, or replace the appropriate motor;

6) Check whether the fan blade is not fixed or whether the fan blade is damaged if necessary.

When the motor runs at no-load, the current is unbalanced and varies greatly


1) Unbalanced power supply voltage;

2) Winding failure, such as inter turn short circuit, reverse connection of a group of coils, etc;

3) During rewinding, the number of turns of three-phase winding is uneven.


1) Measure the power supply voltage and find out the cause;

2) Disassemble the motor, check the winding polarity and fault, and correct or eliminate the fault;

3) Winding rewinding.

Expert Help and Customized Price Quotes

Need a price quote or have questions? Contact us and let us know your detailed requirements. Our experts will provide you with personalized assistance and a competitive price quote.

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *