If a motor suddenly stops running while it was running fine, you must first check for any significant changes in the load, whether there is any mechanical jamming, and whether anything is obstructing the load; remove any foreign objects immediately. First, make a preliminary assessment to determine if there are any major mechanical problems, and then consider the electrical details.
1. If possible, disconnect the motor and load coupling. Then, manually rotate the motor shaft to check for any jamming issues. First, rule out any internal contact between the motor and the casing, or dry running of the bearings due to lack of lubrication. If the equipment has been stored for a long time, check for oxidation, rust, or corrosion.
2. If it is a newly assembled motor and load, it is necessary to check whether the assembly is over-charged, and whether there is any misalignment in a certain direction, such as not being horizontally aligned, not being concentric, or the rotor being too tight or too loose.
3. If the motor has a driver or similar device, check the driver's historical alarm records to see what the alarm was and address the specific issue for more accurate and timely handling.
4. For newly installed systems, it is also necessary to reconsider whether the motor specification is too small, which may cause overload problems after running for a while. You can measure the load current after the next startup to see if it exceeds the rated motor current. It is possible that the motor is underpowered and stalled. If so, a higher power motor needs to be replaced.
5. From the perspective of the main circuit, there may be short circuits, phase loss, overcurrent, and overload. Motor control designs must consider these issues and include corresponding protection functions. You can first use a multimeter to measure the resistance of the three-phase motor when the power is off to check if it is balanced. Use a megohmmeter to measure the insulation resistance of the coil to ground; generally, it should be above 5 megohms to be considered normal. If the motor itself has an unbalanced three-phase structure or poor insulation to ground, it will need repair. Additionally, carefully check whether the overload, phase loss, overheat, and overcurrent protection devices are appropriately selected and whether their parameters are properly matched.
6. If it is a DC motor, check if severe wear of the carbon brushes or commutator is causing the overcurrent or overload alarm. If it is a permanent magnet motor, it is possible that demagnetization is causing the overcurrent or overload alarm.
7. If there are inverters, servo drives, or similar components, the problem may be caused by issues with the drive or encoder. In this case, you need to check the fault code. If you cannot find the fault code, you can only install a new machine of the same model for comparison testing.
8. The control circuit is more complex. If it's a relay control circuit, the relay coil might be worn out due to overheating, causing insufficient engagement, or the contacts might be faulty, increasing resistance over time and causing malfunctions. In this case, the corresponding self-holding or interlocking relay needs to be replaced. If it's a PLC or CNC system, it could be a software problem, such as a logic error, or a malfunction of an external interlocking switch. These issues need to be diagnosed and identified based on the circuit diagram.
9. Power supply voltage fluctuations may also cause the motor to stop working momentarily. Voltage breakdown of the motor is relatively rare, but it has been seen. However, severe voltage fluctuations are more likely to affect the control system, which can directly cause the control system to malfunction and the motor to stop working.
