As a highly reliable power equipment, asynchronous motor maintenance often seems overlooked. However, the principle of "prevention is better than cure" is crucial for motors. A sound and comprehensive maintenance procedure can effectively prevent failures, extend equipment life, and ensure production continuity.
I. Daily and Periodic Maintenance Content
In-Operation Inspections:
Listen to the Sound: There should be no unusual noise during smooth operation. A heavy "humming" sound may indicate overload or phase loss; a periodic "gurgling" sound may indicate bearing damage; an uneven friction sound may indicate stator and rotor rubbing.
Measure Vibration: Excessive vibration is a sign of mechanical or electrical imbalance and requires instrumentation.
Smell: A strong odor of insulating varnish is a clear sign of winding overheating and requires immediate shutdown and inspection.
Check Current: Use a clamp meter to measure the three-phase current to verify that it is balanced and within the rated value. Severe imbalance in the three-phase current is a significant precursor to faults (such as phase loss or inter-turn short circuit).
Regular Inspections During Shutdown:
Cleaning: Thoroughly remove dust and oil from the inside and outside of the housing, as well as between the heat sink ribs, to ensure proper heat dissipation.
Insulation Resistance Test: Use a megohmmeter to measure the insulation resistance between the winding and ground (housing) and between phases. The value should be no less than 1MΩ (refer to the manufacturer's specifications for specific values).
Bearing Inspection and Lubrication: Check the bearings for looseness and abnormal noise. Regularly replace or refill with the specified brand of grease based on operating hours or manufacturer requirements, using 1/2 to 2/3 of the bearing cavity. Excessive grease may cause overheating.
Tightening Inspection: Check the anchor bolts, end cover bolts, and wiring terminals for looseness.
II. Common Fault Symptoms and Cause Analysis
Unable to start and no sound:
Cause: Power is not connected (circuit breaker tripped, fuse blown), motor lead wire is broken, or internal winding is open.
Unable to start and there is a buzzing sound:
Cause: This is a typical "stall" phenomenon. Possible causes include: missing power phase (single-phase operation), excessive or stuck load, broken rotor bars (squirrel cage type), and bearing damage and seizure.
Low speed and rapid temperature rise after startup:
Causes: Excessive load, low power supply voltage, broken rotor bars (manifested by periodic fluctuations in the speed and ammeter needles), and single-phase operation.
Abnormal noise and vibration during operation:
Causes: Excessive bearing wear clearance, unstable base installation, coupling misalignment, fan blade contact with the housing, and poor rotor dynamic balancing.
Motor overheating:
Electrical causes: Overload, excessively high or low power supply voltage, missing phase operation, inter-turn or inter-phase short circuits in the winding, and frequent starting.
Mechanical causes: Increased friction due to poor bearing lubrication or damage.
Environmental causes: Excessive ambient temperature and blocked ventilation ducts.
III. Fundamental Maintenance Recommendations
Establishing a motor "health record" that records every maintenance, inspection, and repair is the foundation for predictive maintenance. For critical equipment, condition monitoring technologies such as vibration analysis and infrared thermal imaging can be introduced to detect early signs of failure before they occur.
Systematic maintenance and accurate fault diagnosis of asynchronous motors are not rocket science, but rather a management art based on meticulous observation and standardized operation. Investing minimal time and cost in preventive maintenance is far less costly than the production downtime and expensive repairs caused by sudden failures.
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Aolong Motor Technology
