Troubleshooting 9 Common Motor Faults: Expert Methods and Tips

As industrial machines become more complex, motor faults can become a common issue that can lead to significant downtime and production losses.

But fear not, our comprehensive guide provides troubleshooting methods for a range of motor faults, from overheating and smoking to abnormal noises and low insulation resistance.

Whether you’re a seasoned engineer or a novice technician, our expert advice will help you identify and resolve motor faults quickly and efficiently, ensuring your machines are up and running in no time.

So, let’s dive in and discover the secrets to keeping your motors running smoothly.

The motor cannot be started.


  1. The motor’s power supply is not connected;
  2. An open circuit in the winding;
  3. Grounding or short circuit between phases in the winding;
  4. Incorrect wiring of the winding;
  5. Burnout of the motor’s melt;
  6. Incorrect wiring of the control equipment.


  1. Check the switch, melt, and each contact point and the outgoing wire head of the motor;
  2. To repair an open circuit, heat the affected part to the temperature allowed by the insulation grade to soften the paint, pick up the wire, repair the broken part with wires of the same specification, wrap with insulation, and then paint and let it dry;
  3. The same method is used for grounding or short circuit parts, but the affected parts are padded with insulation before painting and drying;
  4. To correct wiring errors, check the wiring diagram, heat the ends, and reconnect according to the correct method, which includes binding, insulation treatment, and painting;
  5. To resolve a burnout, determine the cause, eliminate the fault, and prepare a new melt according to the motor’s specifications;
  6. To correct incorrect wiring of the control equipment, simply correct the wiring.

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


  1. Single-phase starting of the motor;
  2. Overloading or jamming of the motor;
  3. Insufficient cross-sectional area of the melt;
  4. Short circuit in the connecting line between the power supply and the motor.


  1. Check the contact points of the power line, outgoing line of the motor, fuse, and switch, and repair any broken lines or incorrect connections that are found;
  2. Adjust the load to the rated value and resolve any faults in the towing mechanism;
  3. The melt may not protect the motor from overloading. Generally, the melt should be selected using the formula: Melt rated current = starting current / (2 to 3);
  4. Check for the short circuit point and repair it.

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


  1. Jamming or overloading of the motor;
  2. Incomplete connection of the power supply;
  3. Low voltage;
  4. Hard grease or too tight assembly in small motors.


  1. Check the equipment and resolve any faults;
  2. Replace the fuse melt and tighten loose screws of the terminal. Use a multimeter to check for disconnections or incorrect connections in the power line and repair as necessary;
  3. If a delta connection motor is incorrectly connected as a Y connection, it should be changed back to delta connection. If the power supply voltage is too low, contact the power supply department for a solution. If the voltage drop in the power line is too large and the voltage is too low, change to a thicker cable;
  4. Use appropriate grease to improve the assembly quality.

The motor housing is charged.


  1. Incorrect power line and grounding wire connections;
  2. Moisture in the motor winding and serious aging of the insulation;
  3. Grounding of the outgoing line with the junction box.


  1. Correct the errors;
  2. Dry the motor and replace the aged insulation;
  3. Wrap or renew the insulation on the 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. Low voltage in the power supply;
  2. Delta connection winding is incorrectly connected as Y connection;
  3. Open welding or fracture in the cage rotor;
  4. Overwinding during rewinding.


  1. Use a voltmeter or multimeter to check the input power voltage of the motor and resolve the issue;
  2. Change the Y connection back to delta connection;
  3. After checking, repair any open welding or fractures;
  4. Rewind the motor with the correct number of turns.

Low insulation resistance


  1. Moisture in the winding or water damage;
  2. Aging of the winding insulation.


  1. Heat the winding to dry it;
  2. After identifying the issue, the winding can be used continuously. Clean, dry, and repaint the winding. If the insulation is too old to operate safely, it should be replaced.

Abnormal noise during motor operation


  1. Worn or faulty bearings;
  2. Loose stator and rotor iron core;
  3. High or unbalanced voltage;
  4. Lack of lubricating grease in the bearings;
  5. Fan touching the hood or blockage in the air duct;
  6. Uneven air gap causing friction between the stator and rotor.


  1. Repair or replace the bearings;
  2. Identify the cause of vibration and re-compress the iron core for treatment;
  3. Measure the power supply voltage and address the causes of high voltage and imbalances;
  4. Clean the bearing and fill it with grease until it is half to two-thirds full in the bearing chamber;
  5. Correct the size of the fan and hood and repair them, clean the ventilation duct;
  6. Adjust the air gap to improve the assembly quality.

Motor overheating or smoking


  1. Overly high power supply voltage leading to saturation of the iron core magnetic flux density and increased motor temperature;
  2. Low power supply voltage resulting in high motor temperature rise under rated load;
  3. Friction between the stator and rotor iron cores;
  4. Overloading or high resistance in production machinery causing the motor to overheat;
  5. Frequent motor starting or excessive forward and reverse rotation;
  6. Fan failure or inadequate ventilation.


  1. If the power supply voltage is significantly above the standard, contact the power supply department for a solution;
  2. If the issue is caused by excessive voltage drop in the power line, replace it with a thicker power line;
  3. If the power supply voltage is too low, contact the power supply department to increase the voltage;
  4. Eliminate faults in the driving machinery and reduce resistance;
  5. If the rated current exceeds, reduce the load, replace the motor with a larger capacity, or take capacity pulling measures;
  6. Reduce the number of motor starts, forward and reverse rotations, or replace the appropriate motor;
  7. If necessary, check if the fan blade is loose or damaged and repair or replace it.

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


  1. Imbalanced power supply voltage;
  2. Failure in the winding, such as inter-turn short circuit or reverse connection of a group of coils;
  3. Uneven number of turns in the three-phase winding during rewinding.


  1. Measure the power supply voltage and identify the cause;
  2. Disassemble the motor, inspect the winding polarity and faults, and correct or eliminate the issues;
  3. Rewind the winding.

Professional Insights

Get Expert Advice on Metalworking Machines

Let our experts help you choose the right metalworking machine for your needs.

About The Author

Leave a Comment

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

Scroll to Top