The key points of the daily maintenance and inspection of electric motors are to detect the abnormal status of the equipment as early as possible, deal with it in a timely manner, and prevent the accident from expanding. Maintenance personnel can discover abnormal phenomena based on the operation and signals of the relay protection device, and they can also rely on their own experience to judge the signs of potential accidents.
- First, conduct a visual inspection.
Through visual inspection, the following abnormal phenomena can be detected: Check if the external fasteners of the motor are loose, if any components are damaged, and if there is oil contamination or corrosion on the equipment surface. Also, examine if there are any signs of discoloration, burn marks, or smoke at the contact points and connections of the motor. These phenomena may be caused by local overheating of the motor, poor conductor contact, or winding burnout. Check if the instrument readings are normal. If the voltmeter shows no indication or abnormal readings, it may indicate unbalanced power supply voltage, blown fuses, unbalanced three - phase resistance of the rotor, single - phase operation, or poor conductor contact. If the ammeter shows an excessive reading, it may indicate motor overload, bearing failure, or inter - turn short - circuit in the winding. If the motor stops running, possible causes include power outage, single - phase operation, low voltage, insufficient motor torque, excessive load, excessive voltage drop, burned - out bearings, or mechanical jamming.
- Use a stethoscope to listen to various noises of the motor.
By listening, you can hear electromagnetic noise, ventilation noise, mechanical friction noise, bearing noise, etc., which can help you determine the cause of the motor failure. Mechanical reasons for excessive noise include bearing failure, mechanical imbalance, loose fastening screws, improper coupling connection, and rubbing between the stator and rotor cores. Electrical reasons include unbalanced voltage, single - phase operation, winding open - circuit or breakdown faults, poor starting performance, and poor acceleration performance.
- Use your sense of smell to detect a burnt or foul odor.
The causes of such odors may be motor overheating, winding burnout, single - phase operation, winding faults, or bearing failures.
- Use your sense of touch to feel the motor casing surface for over - temperature and vibration.
Causes of vibration include unbalanced mechanical load, loose fastening components, insufficient strength of the motor foundation, improper coupling connection, uneven air gap or foreign matter intrusion, unbalanced voltage, single - phase operation, winding faults, and bearing failures.
Causes of over - temperature of the motor include overload, blocked cooling air ducts, single - phase operation, inter - turn short - circuit, excessive or low voltage, unbalanced three - phase voltage, poor acceleration characteristics leading to long starting time, rubbing between the stator and rotor, poor contact of the starter, frequent starting, braking or reverse - braking, high inlet air temperature, and mechanical jamming.
When estimating the temperature of the motor surface by hand, since everyone's perception is different and it is subjective, it should be judged based on experience.
Routine maintenance inspections are divided into daily inspections, monthly or regular patrol inspections, and annual inspections.
In daily inspections, mainly check the lubrication system, appearance, temperature, noise, vibration, and abnormal phenomena. Also, check the ventilation and cooling system, sliding friction conditions, and the fastening of each component, and carefully record the inspection results.
In monthly or regular inspections, mainly check if there are any loose parts in switches, wiring, and grounding devices, and if there are any damaged parts. If so, plans and repair measures should be proposed. Check the dust accumulation and clean it in time. Examine if there are any damages or aging problems in the lead - out wires and wiring. Test and record the insulation resistance of the motor winding.
In addition to the above - mentioned items, the annual inspection also includes disassembling the motor for core inspection, cleaning the oil and dirt, and checking the insulation.
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