Motor common fault analysis - Solutions - Huaqiang Electronic Network

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1. Starting Faults: When the device is turned on, the motor does not operate and makes no sound. This issue often stems from a mismatch between the starting component and the motor. For example, fans, exhaust fans, and washing machines typically use capacitors for starting, while refrigerators and freezers use a resistor-based phase-start method. If the capacitor or resistor in the starting circuit fails, the motor may not work properly. Before checking the motor itself, it’s essential to rule out issues with the starting components. In some cases, internal winding damage or short circuits can cause the motor to stop working. A simple way to test this is by using a multimeter to measure the resistance of each winding. For instance, in a double-bucket washing machine motor, if the resistance between AB is 95 ohms, BC is 130 ohms, and AC is 12 ohms, it indicates that C is the center line, AC is the running winding, and BC is the starting winding. If the resistance drops significantly, it may signal a short circuit or damaged winding. 2. Operational Faults: Motors can fail during operation due to mechanical or electrical issues. 2.1 Mechanical Failures: These include issues like bearing overheating, rotor-stator friction, or misalignment. A small air gap between the stator and rotor can lead to collisions. Worn bearings, deformed end caps, or uneven foundations can also cause vibration and noise. If the motor runs slowly, it could be due to low capacitor capacity, insufficient voltage, or damaged rotor bars. In washing machines, frequent direction changes can cause the rotor bars to break, leading to poor performance and overheating. 2.2 Electrical Faults: These involve issues like phase loss, unbalanced current, winding short-circuiting, or grounding. Phase loss occurs when one of the three phases is disconnected, causing the motor to run out of balance. This can result in excessive current and potential damage. Incorrect winding connections or imbalanced voltages can also cause problems. Ground faults can be detected using a megohmmeter, while short circuits can be identified through resistance testing. Overheating is another common problem, often caused by prolonged overload, poor ventilation, or internal winding damage. Turn-to-turn short circuits are particularly dangerous, as they create low-impedance loops that increase current and heat. If left unchecked, this can destroy the winding. In cage motors, broken rotor bars can cause irregular currents and increased noise. 3. Motor Maintenance: Proper care extends the life of the motor. Keep the environment dry and clean, and ensure the air intake is unobstructed. Regularly check the thermal protection system and lubricate the bearings every 5000 hours. Replace grease when necessary, and always follow manufacturer guidelines when rewinding. Disassemble the motor carefully to avoid damaging the windings, and document all specifications when replacing parts. By maintaining your motor regularly, you can prevent many common failures and ensure smooth operation.