In industrial transmission systems, the reduction motor, as the core power component, is widely used in various fields such as mechanical manufacturing, mining and metallurgy, chemical building materials, logistics and transportation. Its operating status directly affects the continuity and stability of the entire production process. In daily use, due to various factors such as working conditions, operating standards, and maintenance levels, the reduction motor is prone to various faults. If not diagnosed and properly repaired in a timely manner, it may lead to equipment shutdown, production interruption, increased operation and maintenance costs, and even safety hazards. Currently, many enterprises lack professional fault diagnosis and maintenance experience, and often have no way to deal with gearbox motor faults, delaying the repair time.
The faults of deceleration motors are mainly concentrated in the electrical system, mechanical structure, and lubrication system. Common faults mainly include winding faults, bearing faults, sealing faults, abnormal speed, and overload faults. Fault diagnosis should follow the principle of "appearance first, internal second; electrical first, mechanical second; static first, dynamic second", combined with fault phenomena and operating conditions, accurately locate the cause of the fault through intuitive observation, instrument detection, experience judgment, and other methods, and then take targeted maintenance measures to avoid blind disassembly leading to the expansion of the fault.
1、 Diagnosis and maintenance of winding faults (electrical core faults)
The winding, as the "heart" of the deceleration motor, has a high failure rate. Common faults include winding short circuit, insulation aging, winding open circuit, etc., which are often caused by factors such as dust intrusion, humid environment, overload operation, and improper wiring. The core diagnostic point is to combine visual observation with instrument detection to accurately determine the type of fault.
In terms of fault diagnosis, if the deceleration motor fails to start, trips during operation, heats up severely, and is accompanied by a burnt smell, it is mostly a winding short circuit fault. By visually observing the surface of the winding, if discoloration, adhesion, or burn marks are found on the winding coil, or if a multimeter is used to detect the winding resistance, and the resistance value is far below the standard value or even zero, it can be diagnosed as a short circuit. If the speed of the motor is unstable and there is leakage during operation, and the multimeter detects that the insulation resistance of the winding is lower than 1M Ω, it is mostly due to aging or damage of the winding insulation. Further inspection is needed to check whether there is dust accumulation or damage marks on the surface of the winding. The winding open circuit fault is manifested as the motor being unable to start and having no output torque. Use a multimeter to check the resistance of each phase of the winding. If the resistance of one phase is infinite, it can be determined that the winding of that phase is open circuit.
The repair method should be targeted according to the type of fault: for winding short circuits, if the short circuit range is small and does not cause coil burnout, the surface dust and debris of the winding can be cleaned, the damaged part can be repaired with insulating tape, and then re dried before being put into use; If the short circuit range is large and the coil is severely burned, the motor needs to be disassembled, the winding coil needs to be replaced, and suitable insulation materials (F or H grade) should be selected according to the original specifications. The coil should be rewound and dried. For insulation aging, it is necessary to thoroughly clean the dust and oil stains on the surface of the winding, reinforce the insulation layer, and replace the entire winding if the aging is severe. For winding open circuit, the open circuit point can be found and re welded for repair. If there are too many open circuit points, the winding coil needs to be replaced. After repair, the insulation resistance needs to be tested to ensure compliance with operating standards.
2、 Diagnosis and maintenance of bearing faults (mechanical core faults)
Bearings are the "hub" for the rotation of deceleration motors, and common faults include bearing wear, jamming, overheating, abnormal noise, etc., which are often caused by factors such as dust intrusion, insufficient lubrication, installation deviation, etc. Their faults can easily cause motor vibration, speed drop, and even shutdown. The diagnosis of bearing faults can be done through three methods: listening, watching, and measuring, which are easy to operate and do not require complex instruments.
When diagnosing faults, the first step is to use auditory judgment: if there is a "buzzing" abnormal sound, "rustling" friction sound, or "clanging" stuck sound when the motor is running, it is mostly due to bearing wear, insufficient lubrication, or dust intrusion; Secondly, through visual observation, if there is lubricating oil leakage, wear marks on the bearing surface, or surface discoloration caused by high temperature at the bearing end cover, a preliminary diagnosis of bearing failure can be made; Finally, through instrument testing: use a thermometer to measure the temperature of the bearing. If the temperature exceeds 80 ℃ and continues to rise, or use a multimeter to measure the vibration value of the bearing. If it exceeds the standard range, the bearing fault can be diagnosed.
The maintenance method should be combined with the severity of the fault: if the bearing is only slightly worn and lacks lubrication, the bearing end cover can be disassembled, the dust and oil on the bearing surface can be cleaned, special lubricating grease (dust resistant, high temperature resistant) can be replaced, the bearing can be reinstalled and the seal strengthened to ensure that no dust enters; If the bearing is severely worn, stuck, or the ball is damaged, it is necessary to replace it with a high-precision bearing of the same specification. During installation, adjust the coaxiality to avoid secondary wear caused by installation deviation; If the bearing chamber is damaged, it is necessary to repair the bearing chamber or replace the end cover to ensure that the bearing is installed firmly and rotates flexibly. After maintenance, a no-load test run is required to check the bearing temperature and vibration values to ensure compliance with operational requirements.
3、 Diagnosis and maintenance of sealing faults (suitable for dust/humid working conditions)
Sealing failure is a common fault of deceleration motors, especially in dusty and humid environments, which can easily lead to dust intrusion, lubricating oil leakage, and internal component damage. Common faults include lubricating oil leakage, dust accumulation, and water ingress inside the motor. Diagnosis and maintenance should focus on key sealing parts.
When diagnosing faults, visually observe the sealing parts of the motor. If lubricating oil leaks out or dust accumulates at the bearing end cover, junction box, or shaft extension, or if there is abnormal noise or unstable speed during motor operation, it is often caused by aging or damage to the sealing components. Touch the sealing area with your hand, and if you feel that the seal is loose or hard, or if you observe cracks or deformation in the seal, it can be determined as a sealing failure. In addition, if there is water accumulation or dust accumulation inside the motor, it can also be diagnosed as seal failure.
The maintenance method is centered on "strengthening sealing and replacing damaged parts": replacing aging and damaged sealing rings and dust-proof retaining rings, focusing on optimizing the sealing structure of key parts such as bearing end caps, junction boxes, and shaft extensions; Clean the dust and oil stains in the sealed gaps to ensure a smooth and tight sealing surface; The sealing failure of the junction box requires replacement of the sealing gasket and dust cover, re tightening of the wiring terminals to prevent dust from entering; If the gap between the shell is too large, it needs to be sealed and reinforced to avoid seal failure. After maintenance, a sealing test is required to ensure that no dust or water vapor enters before putting it into use.
4、 Diagnosis and maintenance of abnormal speed and overload faults
During the operation of a deceleration motor, abnormal speed and overload faults are common, often caused by factors such as load fluctuations, power mismatch, electrical faults, etc., manifested as too fast, too slow, unstable speed, or motor overheating, tripping, etc. If not dealt with in a timely manner, it can easily lead to motor burnout.
When diagnosing faults, the first step is to check the motor load. If the load exceeds the rated load and the motor overheats or trips, it is often an overload fault. The current value can be detected through an ammeter. If the current exceeds the rated current, a diagnosis can be made; If the motor speed is unstable, difficult to start, and accompanied by insufficient torque, it is often caused by abnormal power supply voltage, winding failure, or load jamming; If the motor speed is too fast and there is no load fluctuation, it is mostly an electrical control failure (such as abnormal frequency conversion control).
The maintenance method needs to be targeted: for overload faults, the load should be checked first, dust blockage should be cleared, and the load should be adjusted to the rated range. If the motor power reserve is insufficient, the motor with the appropriate power should be replaced; Unstable speed requires checking the power supply voltage to ensure voltage stability, troubleshooting winding faults, repairing insulation or replacing windings; If it is a variable frequency control motor, it is necessary to check the parameters of the variable frequency equipment, adjust the frequency and torque adaptation values, and avoid speed fluctuations caused by abnormal parameters. At the same time, it is necessary to check the motor cooling system, clean the dust accumulation on the cooling ribs, ensure smooth heat dissipation, and avoid overheating causing abnormal speed.
5、 Common troubleshooting and maintenance precautions
When repairing a deceleration motor, it is necessary to follow the principle of "safety first, standardized operation" to avoid safety accidents or secondary failures during the repair process. Firstly, the power supply should be cut off before maintenance, and a "Do not close, under maintenance" sign should be hung. Wait for the motor to completely cool down before disassembling to prevent electric shock and burns; Secondly, when disassembling the motor, follow the standard procedures, mark the components properly, and avoid component loss or installation misalignment; During the maintenance process, use accessories of the same specifications and models, especially bearings, seals, and winding coils, to ensure compatibility with the motor operating conditions; After maintenance, a no-load test run is required to detect parameters such as motor speed, temperature, and vibration. After confirming that there are no abnormalities, the motor can be put into load operation.
Industry experts remind that in daily operation and maintenance, enterprises should establish a fault diagnosis ledger, record fault phenomena, diagnostic processes, maintenance methods, and replacement parts, summarize fault patterns, and take preventive measures in advance. At the same time, strengthen the professional training of operation and maintenance personnel, enhance their fault diagnosis and maintenance capabilities, and avoid blind disassembly leading to the expansion of faults. For complex faults that cannot be self diagnosed and repaired, it is necessary to contact professional maintenance personnel and combine professional instrument testing to ensure the quality of maintenance.
Currently, with the continuous upgrading of deceleration motor technology, fault diagnosis methods have become more convenient. Many enterprises adopt intelligent monitoring equipment to monitor motor operating parameters in real time, warn of potential faults in advance, and reduce downtime caused by faults. Next, relevant industries will further improve the fault diagnosis standards for deceleration motors, promote convenient and efficient diagnosis and maintenance technologies, help enterprises reduce operation and maintenance costs, and enhance production continuity.
