Motor overload failure means that the current carried by the motor during operation exceeds its design rating, causing the motor to overheat, be damaged, or stop working. The following are some characteristics of motor overload failure and possible causes:

Characteristics:

1. Overheating: The surface temperature of the motor rises abnormally, and there may even be a burning smell.

2. Excessive current: The current exceeds the rated current when the motor is running.

3. Speed reduction: The motor speed decreases, and in severe cases, it may stop.

4. Sound and vibration: Low sound and vibration occur when the motor is running.

5. Burnt smell and black smoke: When the motor is severely overloaded, there may be a burnt smell around the motor, even accompanied by black smoke.

6. Winding damage: The insulation part of the winding is black and brittle. In severe cases, the insulation layer is carbonized into powder.

Cause analysis:

1. Overload: The actual operating power of the motor exceeds the rated power, resulting in overload.

2. Phase-loss operation: One or more phases of the three-phase power supply of the motor are missing, causing unbalanced operation of the motor.

3. Voltage problem: The operating voltage exceeds the rated voltage allowable value, causing the motor winding to heat up.

4. Mechanical failure: If the bearing is damaged or the mechanical jams, the motor speed will drop or stagnate.

5. Misoperation during the test: If the stall test time is too long, or the test equipment capacity is insufficient, the motor winding will overheat.

6. Wiring error: The star-connected motor is mistakenly connected in a triangle connection, or the voltage is too high when testing the motor with a different frequency and voltage.

7. Power supply problem: The power supply voltage is too high or too low, causing the winding to heat up.

8. Impact load: The load suddenly increases, causing the motor speed to suddenly decrease.

9. Bearing system failure: Bearing damage or scavenging stops, causing the motor to overload.

Troubleshooting methods:

1. Check the load: Confirm whether the motor is correctly selected and matched to the load.

2. Measure the current: Use an ammeter or clamp meter to measure the actual power consumption of the motor and compare it with the rated value on the nameplate.

3. Check the protection device: Confirm whether the motor starter protection device is correctly installed and adjusted.

4. Clean the vents: Clean the motor surface and vents regularly to remove debris obstructing airflow.

5. Check the motor wiring: Make sure the motor wiring is correct and there are no wiring errors.

6. Check the power supply: Ensure the voltage is stable and within the allowable range.

Through the above characteristics and cause analysis, the motor overload fault can be effectively identified and handled to ensure the safe and stable operation of the motor.