I. Introduction Due to the long service life of most motors, and the fact that many operate in harsh environments year after year, motor burnout accidents are frequent and on the rise, seriously affecting the safe, reliable, and long-term operation of production. This article provides a brief analysis and introduction to the causes of motor burnout and corresponding countermeasures, hoping to be helpful to those engaged in electrical work and safety management.　　II. Causes and Countermeasures for Partial Burnout of Motor Windings 1. Due to poor sealing of the motor itself, coupled with leaks and spills in the environment, water or other corrosive liquids or gases can enter the motor, causing corrosion of the motor winding insulation. The most severely affected areas or the weakest points in the insulation may experience point-to-ground, phase-to-phase, or turn-to-turn short circuits, leading to partial burnout of the motor windings. Corresponding countermeasures: ① Minimize leaks and spills in the process and machinery; ② During maintenance, ensure proper sealing of every part of the motor, such as applying a small amount of 704 sealant to each flange, applying grease to bolts, and installing anti-splash boxes at junction boxes if necessary. Protective covers should be installed where the motor is exposed to easily intruded liquids and contaminants; ③ For motors operating in this environment, shorten the minor and intermediate repair cycles, and perform intermediate repairs promptly in severe cases. 2. Due to bearing damage, shaft bending, or other reasons, friction between the stator and rotor (commonly known as rotor rubbing) causes a rapid rise in core temperature, burning out slot insulation and turn-to-turn insulation, resulting in turn-to-turn short circuits or "explosion" to ground in the windings. In severe cases, it can cause stator core slotting, misalignment, shaft wear, and end cover failure. Bearing damage is generally caused by the following reasons: ① Improper bearing assembly, such as uneven tapping of the bearing inner ring during cold assembly, causing shaft wear, resulting in a loss of interference fit between the bearing inner ring and the bearing, or a decrease in interference fit, leading to inner ring slippage. Uneven tapping during motor end cover assembly can cause the end cover bearing housing and bearing outer ring to have an excessively loose fit, resulting in outer ring slippage. Both inner and outer ring slippage will cause a sharp rise in bearing operating temperature, leading to burnout. In particular, inner ring slippage will cause severe shaft wear and bending. However, intermittent outer ring slippage generally will not cause a sharp rise in bearing temperature, and intermittent outer ring slippage is permissible as long as the bearing is intact. ② The bearing cavity is not cleaned properly or the grease applied is not clean. For example, if small rigid substances in the bearing cage are not thoroughly cleaned, the bearing raceway will be damaged during operation, causing excessive temperature rise and burning out the bearing. ③ The bearing was replaced and re-machined. Excessive interference fit or excessive ellipticity after the motor end cover was nested caused insufficient or uneven ball clearance, leading to increased friction during operation, a rapid temperature rise, and eventual burnout. ④ Axial misalignment of the stator and rotor cores or insufficient precision after re-machining of the shaft caused the inner and outer rings of the bearing to be on different planes, resulting in the bearing experiencing "interference" during operation, leading to temperature rise and eventual burnout. ⑤ Excessive temperature rise of the motor body during operation, coupled with untimely replenishment of grease, caused bearing lack of lubrication and even burnout. ⑥ Mixing different types of grease caused bearing damage. ⑦ Manufacturing quality problems with the bearing itself, such as raceway rust, inflexible rotation, excessive clearance, cage deformation, etc. ⑧ The standby machine has not been used for a long time, resulting in deteriorated grease and rusted bearings without intermediate repair. Corresponding countermeasures: ① When disassembling and assembling bearings, they should generally be heated to 80℃～100℃, such as by using a bearing heater or boiling in transformer oil. Only in this way can the assembly quality of the bearing be guaranteed. ② Before installing bearings, they must be thoroughly cleaned. No impurities should remain in the bearing cavity, and the grease must be clean before adding it. ③ Avoid unnecessary shaft machining and motor end cover nesting. ④ When assembling the motor, ensure the stator and rotor cores are aligned and not misaligned. ⑤ The motor casing must be clean and of its original color. Ventilation must be guaranteed, the cooling system must be free of scale, and the fan blades must be in good working order. ⑥ Do not mix different types of lubricating grease. ⑦ Before installing bearings, conduct a comprehensive and thorough inspection to ensure their integrity. ⑧ For motors that have not been used for a long time, a necessary disassembly inspection must be performed before use, and the bearing grease must be replaced. 3. Due to the long winding ends or localized damage, friction with the end cover or other accessories can cause partial burning of the windings. Corresponding countermeasures: When replacing motor windings, the windings must be wound according to the original specifications. During motor maintenance, no rigid objects are allowed to touch the windings. When removing the rotor core, the rotor must be lifted to prevent friction between the stator and rotor cores. When using open flames, the windings must be isolated from the flames and a certain distance must be maintained. Before reinstalling the motor, the integrity of the windings must be carefully checked and confirmed. 4. Due to prolonged overload or overheating operation, the winding insulation ages rapidly, and carbonization at the weakest point of the insulation causes inter-turn short circuits, phase-to-phase short circuits, or short circuits to ground, leading to partial burnout of the windings. Corresponding countermeasures: ① Avoid overload operation of the motor as much as possible. ② Ensure the motor is clean and well-ventilated. ③ Avoid frequent motor starts; if necessary, perform a dynamic balancing test on the motor rotor. 5. The motor winding insulation is subjected to mechanical vibration (such as large current impact during startup, vibration of the driven equipment, motor rotor imbalance, etc.), causing defects such as inter-turn loosening and insulation cracks in the windings. The destructive effect accumulates continuously, and thermal expansion and contraction cause friction on the windings, thus accelerating insulation aging, ultimately leading to the destruction of the first carbonized insulation and even burnout of the windings. Corresponding countermeasures: ① Avoid frequent starts as much as possible, especially for high-voltage motors. ② Ensure that the vibration values ​​of the driven equipment and motor are within the specified range. III. Causes and Countermeasures for Burnout (or Overheating) of One or Two Phases of a Three-Phase Asynchronous Motor Winding If one or two phases of a motor winding burn out (or overheat), it is generally due to single-phase operation. A detailed theoretical analysis will not be provided here, only a brief explanation. Figure 1 shows the case of a three-phase asynchronous motor winding in a delta connection: [img=514,161]http://co.163.com/neteaseivp/resource/paper/doc/2006581147073192632/image001.jpg[/img] Figure 2 Schematic diagram of single-phase operation of a Y-connected motor. When a phase is lost for any reason (as shown in Figure 1b), although the motor can still continue to run, the speed decreases and the slip increases. Phases B and C become series connected and then parallel to phase A. Under constant load, the current in phase A becomes excessive. After prolonged operation, the winding of this phase will inevitably overheat and burn out. Figure 2 shows the case of a three-phase asynchronous motor with a Y-connected winding: After a phase loss (as shown in Figure 2b), the motor can still continue to run, but the speed will decrease significantly, the slip will increase, and the rate at which the magnetic field cuts the conductor will increase. At this time, the B-phase winding is open-circuited, and the A and C-phase windings become connected in series and the current is too large. After running for a long time, both phase windings will burn out simultaneously. [img=551,218]http://co.163.com/neteaseivp/resource/paper/doc/2006581147073192632/image002.jpg[/img] Figure 1 Schematic diagram of a motor with a Y-connection and a single phase loss. It should be noted that if a stopped motor is missing one phase of the power supply and then switched on, it will generally only produce a humming sound and will not start. This is because when a symmetrical three-phase AC current is applied to the motor, a circular rotating magnetic field is generated in the stator core. However, when one phase of the power supply is missing, a single-phase pulsating magnetic field is generated in the stator core, which cannot generate starting torque for the motor. Therefore, a motor cannot start when a phase is missing. However, during operation, the motor generates an elliptical rotating magnetic field with high three-phase harmonic components in the air gap. Therefore, a running motor can still operate after a phase loss, but the magnetic field becomes distorted, and harmful current components increase sharply, ultimately leading to winding burnout. Corresponding countermeasures: Regardless of whether the motor is static or dynamic, the direct harm of single-phase operation is overheating or even burnout of one or two phase windings. Simultaneously, overcurrent operation of the power cable accelerates insulation aging. Especially in static conditions, a single phase loss will generate a locked-rotor current several times the rated current in the motor windings. The winding burnout speed is faster and more severe than a sudden single-phase loss during operation. Therefore, while performing routine maintenance and repairs on the motor, a comprehensive inspection and testing of the corresponding MCC functional units is essential. In particular, the reliability of the load switch, power lines, and static and dynamic contacts must be carefully checked. Single-phase operation must be prevented. IV. Summary of common problems, see attached table. V. To standardize motor maintenance and ensure maintenance quality, the following motor process card is established: Low-voltage AC asynchronous motor maintenance process card [table=98%][tr][td=2,1,87]Equipment Name[/td][td=3,1,212][/td][td=1,1,96]Maintenance Unit[/td][td=4,1,216][/td][/tr][tr][td=2,1,87]KKS Code[/td][td=3,1,212][/ [td][td=1,1,96]Work Supervisor[/td][td=4,1,216][/td][/tr][tr][td=2,1,87]Equipment Model[/td][td=3,1,212][/td][td=1,1,96]Work Members[/td][td=4,1,216][/td][/tr][tr][td=2,1,87]Maintenance Time[/td][td=8,1,525]Year Month Day Hour Minute ———— [Year, Month, Day, Hour, Minute][/td][/tr][tr][td=10,1,612] Work Tools [/td][/tr][tr][td=1,1,48]Serial Number[/td][td=3,1,192]Name[/td][td=2,1,156]Model Specifications[/td][td=1,1,48]Quantity[/td][td=1,1,48]Unit[/td][td] =2,1,120]Remarks[/td][/tr][tr][td=1,1,48]1[/td][td=3,1,192]□Hand-operated hoist[/td][td=2,1,156][/td][td=1,1,48]2[/td][td=1,1,48]pieces[/td][td=2,1,120][/td][/tr][tr][td=1, 1,48]2[/td][td=3,1,192]□Steel Wire Rope[/td][td=2,1,156][/td][td=1,1,48]2[/td][td=1,1,48]Pieces[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]3[/td][td=3,1,192]□U-Shaped Ring[/td] [td=2,1,156][/td][td=1,1,48]4[/td][td=1,1,48]each[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]4[/td][td=3,1,192]□Special tool for removing and installing rotors[/td][td=2,1,156][/td][td=1,1,4] 8]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]5[/td][td=3,1,192]□Special tools for pulling out the wheel and fan blades[/td][td=2,1,156][/td][td=1,1,48]1 each[/td][td=1,1,48]set[/t] d][td=2,1,120][/td][/tr][tr][td=1,1,48]6[/td][td=3,1,192]□Bearing puller[/td][td=2,1 ,156][/td][td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td= 1,1,48]7[/td][td=3,1,192]□Hex wrench[/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]8[/td][td=3,1,192]□Sledgehammer[/ td][td=2,1,156]8 pounds[/td][td=1,1,48]1[/td][td=1,1,48][/td][td=2,1,120][/td][ /tr][tr][td=1,1,48]9[/td][td=3,1,192]□Hand hammer[/td][td=2,1,156]1.5 pounds[/td][td=1,1, 48]1[/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1,1,48]10[/td][td =3,1,192]□Oil pan[/td][td=2,1,156][/td][td=1,1,48]2[/td][td=1,1,48][/td][td=2, 1,120][/td][/tr][tr][td=1,1,48]11[/td][td=3,1,192]□ Copper Rod[/td][td=2,1,156]Ф60, Red Copper[/td][td=1,1,48]1[/td][td=1,1,48]Piece[/td][td=2,1,120][/td][/tr][tr][td=1, 1,48]12[/td][td=3,1,192]□ Electrician's Tool Set[/td][td=2,1,156]24 pieces[/td][td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]13[/td][td=3,1,192]□ Tapping wrench[/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]handle[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]14[/td][td=3,1,192]□ box wrench[/td][td=2,1,156]8-12[/td][ td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]15[ /td][td=3,1,192]□ Adjustable wrench[/td][td=2,1,156]18[/td][td=1,1,48][/td][td=1,1,48][/t d][td=2,1,120][/td][/tr][tr][td=1,1,48]16[/td][td=3,1,192]□Grill handle[/td][td=2,1, 156][/td][td=1,1,48]1[/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1 17 [td] [td=3,1,192]□ Crowbars[/td] [td=2,1,156] Large and Small[/td] [td=1,1,48] 2 each[/td] [td=1,1,48] 18 [td] [td=3,1,192]□ Blower/Suction Fan [td=2,1,156]220V, 1000W[/td][td=1,1,48]1[/td][td=1,1,48]unit[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]19[/td][td=3,1,192]□ Wire reel[/td][td=2,1,156]220 V-belt leakage current protector[/td][td=1,1,48]1[/td][td=1,1,48]piece[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]20[/td][td=3,1,192]□ Brush[/td][td=2,1,156]2 inches[/td][td=1,1,48]2[/td][td=1,1,48]piece[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]21[/td][td=3,1,192]□ Bearing heater[/td][td= 2,1,156]DKQ-V, 220V[/td][td=1,1,48]1[/td][td=1,1,48]pcs[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]22[/td][td=3,1,192]□Flashlight [/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1,1,48]23[/td][td=3,1,192]□道木[/ td][td=2,1,156][/td][td=1,1,48]2[/td][td=1,1,48]root[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]24[/td][td=3,1,192]jack[/t d][td=2,1,156]32T[/td][td=1,1,48]1[/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1,1,48]25[/td][td=3,1,192]□Expansion clamp[/ td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]26[/td][td=3,1,192]□screwdriver[/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]handle[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]27[/td][td=3,1,192]□inner and outer micrometer[ /td][td=2,1,156]0.01mm, 0-25mm～225-250mm[/td][td=1,1,48]1[/td][td=1,1,48]set[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]28 [/td][td=3,1,192]□Meter shaker[/td][td=2,1,156]3121, 1000V[/td][td=1,1,48]1[/td][td=1,1,48]block[/td][td=2,1,120][/td][/tr][tr][td=1 ,1,48]29[/td][td=3,1,192]□Thermometer[/td][td=2,1,156]JIC6802[/td][td=1,1,48]1[/td][td=1,1,48]piece[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]30[/td][td=3,1,192]□Vibration Analyzer[/td][td=2,1,156]EMT220ANC[/td][td=1,1,48]1[/td][td=1,1,48]piece[/td][td=2,1,120][/td] [/tr][tr][td=1,1,48]31[/td][td=3,1,192]□ Listening needle[/td][td=2,1,156]800mm, copper[/td][td=1,1,48]1[/td][td=1,1,48]root[/td][td=2,1,120] [/td][/tr][tr][td=1,1,48][/td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr ][tr][td=1,1,48][/td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td= 1,1,48][/td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1,1,48][/ td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=1,1,48][/td][td=3, 1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=10,1,612] Consumed materials [/td][/tr][tr] [td=1,1,48]Serial Number[/td][td=3,1,192]Name[/td][td=2,1,156]Model[/td][td=1,1,48]Quantity[/td][td=1,1,48]Unit[/td][td=2,1,120]Remarks[/td][/tr][tr][td=1,1,48]1[/td][td=3,1,192]□Grease[/td][td=2,1,156]Same as the grease used in the motor[/td][td=1,1,48]4[/td][td=1,1,48]Kg[/td][td=2,1,120][/ td][/tr][tr][td=1,1,48]2[/td][td=3,1,192]□ Cleaning Agent[/td][td=2,1,156]Ace 25[/td][td=1,1,48]25[/td][td=1,1,48]kg[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]3[/td][td=3,1,192]□ Plastic Sheet[/td][td=2,1,156]Width 1m[/td][td=1,1,48]10[/td][td=1,1,48]m[/td][td=2,1, 120][/td][/tr][tr][td=1,1,48]4[/td][td=3,1,192]□Insulating plastic tape[/td][td=2,1,156]Yellow, green, red[/td][td=1,1,48]1 each[/td][td=1,1,48]roll[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]5[/td][td=3,1,192]□High-voltage self-adhesive tape[/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]reel[/td][t d=2,1,120][/td][/tr][tr][td=1,1,48]6[/td][td=3,1,192]□Oxygen, B Alkynes[/td][td=2,1,156][/td][td=1,1,48]1 each[/td][td=1,1,48]bottle[/td][ td=2,1,120][/td][/tr][tr][td=1,1,48][/td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,12 0][/td][/tr][tr][td=1,1,48][/td][td=3,1,192][/td][td=2,1,156][/td][td=1,1,48][/td][td=1,1,48][/td][td=2,1,120][/td][/tr][tr][td=10,1,612] Spare parts required for maintenance [/td][/tr][tr][td=1,1,48]Serial number[/td][td=3,1,192]Name[/td][td=2,1,156]Model[/td][td=1,1,48]Quantity[/td][ [td=1,1,48]Unit[/td][td=2,1,120]Remarks[/td][/tr][tr][td=1,1,48]1[/td][td=3,1,192]□Load-side bearing[/td][td=2,1,156][/td][td=1,1,48]1[/td][td=1,1,48]Disc[/td][td=2,1,120][/td][/tr][tr][td=1,1,48]2[/td][td=3,1,192]□Non-load-side bearing[/td][td=2,1,156][/td][td=1,1,48]1[/ [td][td=1,1,48]Disk[/td][td=2,1,120][/td][/tr][tr][td=10,1,612] Safety Measures and Precautions [/td][/tr][tr][td=1,1,48]Serial Number[/td][td=3,1,192]Danger Point[/td][td=5,1,300]Prevention Measures[/td][td=1,1,72]Visa Point[/td][/tr][tr][td=1,1,48]1[/td][td=3,1,192]□Personal Injury[/td][td=5,1,300]Power outage, voltage testing, and warning signs; fences should be erected if necessary. Work can only proceed after voltage is depleted. Do not enter energized areas; maintain a safe distance from energized equipment. [td=1,1,72][/td][/tr][tr][td=1,1,48]2[/td][td=3,1,192]□Injury from tools and equipment[/td][td=5,1,300]Use tools and protective equipment correctly.[/td][td=1,1,72][/td][/tr][tr][td=1,1,48]3[/td][td=3,1,192]□Equipment damage[/td][td=5,1,300]Do not touch unrelated equipment. [td=1,1,72][/td][/tr][tr][td=1,1,48]4[/td][td=3,1,192]□Work without a permit[/td][td=5,1,300]Work can only be carried out after a work permit is obtained[/td][td=1,1,72][/td][/tr][tr][td=1,1,48]5[/td][td=3,1,192]□Electronic interference[/td][td=5,1,300]Turn off mobile phones and other communication devices[/td][td=1,1,72][/ [td][/tr][tr][td=1,1,48][/td][td=3,1,192][/td][td=5,1,300][/td][td=1,1,72][/td][/tr][tr][td=10,1,612] Overhaul Items and Process Requirements [/td][/tr][tr][td=1,1,48]Serial Number[/td][td=2,1,168]Overhaul Procedure[/td][td=6,1,324]Process Standards and Precautions[/td][td=1,1,72]Visa Point[/td][/tr][tr][td=1,1,72] [td][/tr][tr][td=1,9,48]Overhaul Procedure[/td][td=2,1,168]□ Junction Box Removal[/td][td=6,1,324]First, confirm isolation, prepare for the work, verify the motor number and copy the nameplate, and mark the parts to be disassembled accordingly.[img=2,2]http://co.163.com/neteaseivp/resource/paper/doc/2006581147073192632/image003.gif[/img] [td=1,1,72][/td][/tr][tr][td=2,1,168]□ Junction Box Inspection[/td][td=6,1,324][img=2,2]http://co.163.com/neteaseivp/resource/paper/doc/2006581147073192632/image003.gif[/img]Check for any leaks or improper sealing. The boxes should be free of dirt. Inspect the sealing rings for aging or damage in sequence (replace if necessary).[/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□ Lead Wire Inspection[/td][td=6,1,324]Check the lead wire insulation and the soldering of the copper lugs and conductors. The conductors should be unbroken and well-insulated. Check the lead wires for overheating, discoloration, deformation, wear, and peeling of the coating. [td=1,1,72][/td][/tr][tr][td=2,1,168]□Remove the anchors and wheel couplings, and lift[/td][td=6,1,324]The lifting operation shall be directed by a professional.[/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□Straighten the wheel couplings[/td][td=6,1,324]When heating the wheel couplings, the temperature shall not exceed 200℃.[/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□Remove the fan cover and remove the fan[/td][td=6,1,324]First remove the fan cover, and then use a special tool to push the fan out. [td=1,1,72][/td][/tr][tr][td=2,1,168]□ Remove the load-side and non-load-side end covers[/td][td=6,1,324] Lift the motor shafts on both sides to prevent stress on the end covers, and use the set screws to push the end covers out. [/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□ Bearing Inspection[/td][td=6,1,324] The bearing's inner and outer slideways, balls, or rollers should be free of peeling, pitting, rust, overheating, scratches, and aging wear. [/td][td=1,1,72]W1[/td][/tr][tr][td=2,1,168]□ Motor Assembly[/td][td=6,1,324] Proceed in the reverse order of disassembly. [td=1,1,72]W2[/td][/tr][tr][td=1,3,48]Reassembly Inspection[/td][td=2,1,168]□Motor Test[/td][td=6,1,324]Insulation resistance and DC resistance tests shall be performed in accordance with the regulations. [/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□Motor Placement[/td][td=6,1,324]After placement, restore the grounding wire and power supply wire. [/td][td=1,1,72][/td][/tr][tr][td=2,1,168]□No-Load Motor Test Run[/td][td=6,1,324]Return the work permit. During the test run, the vibration, temperature, and sound conditions shall meet the requirements of the regulations, and the motor rotation direction shall be checked to ensure it is correct. [td=1,1,72]H1[/td][/tr][/table]Maintenance Record Card Major: _ Date: Year __ Month __ Day [align=center][table=98%][tr][td=1,1,49] System [/td][td=2,1,235][/td][td=1,1,120] Equipment Name [/td][td=1,1,237][/td][/tr][tr][td=5,1,641] Working Conditions Before Maintenance : [/td][/tr][tr][td=5,1,641] Maintenance Status: [/td][/tr][tr][td=5,1,641] Analysis of Problems Found: [/td][/tr][tr][td=5,1,641] Replacement Parts Record (Specifications): [/td][/tr][tr][td=5,1,641] Trial Run Status: [table][tr][td=2,1,156]Operating Current[/td][td=1,1,78]Phase A[/td][td=1,1,78][/td][td=1,1,78]Phase B[/td][td=1,1,78][/td][td=1,1,78]Phase C[/td][td=1,1,78][/td][/tr][tr][td=1,2,78]Motor Vibration[/td][td=1,1,78] Load side[/td][td=1,1,78]―[/td][td=1,1,78][/td][td=1,1,78]⊥[/td][td=1,1,78][/td][td=1,1,78]⊙[ /td][td=1,1,78][/td][/tr][tr][td=1,1,78]Non-load side[/td][td=1,1,78]―[/td][td=1,1,78][/td][td=1, 1,78]⊥[/td][td=1,1,78][/td][td=1,1,78]⊙[/td][td=1,1,78][/td][/tr][tr][td=1,2,78]Motor bearing temperature[/td][td=1,1,78]Load side[/td][td=1,1,78][/td][td=1,2,78]Motor body temperature[/td][td=1,2,78][/td][td=1,2,78] Motor bearing noise [td=1,1,78]Load side[/td][td=1,1,78][/td][/tr][tr][td=1,1,78]Non-load side[/td][td=1,1,78][/td][td=1,1,78]Non-load side[/td][td=1,1,78][/td][/tr][/table][/td][/tr][tr][td=2,1,186] Signature of the person in charge of the work: [td=3,1,455][/td][/tr][tr][td=2,1,186] Work Reviewer's Signature: [/td][td=3,1,455][/td][/tr][tr][td=2,1,186] Equipment Department Head's Signature: [/td][td=3,1,455][/td][/tr][tr][td=5,1,641] Remarks: [/td][/tr][/table][/align] IV. Conclusion From its trial production in 1987 to March 2002, over a period of 15 years, the Kingboard Group suffered over 1,300 instances of motor burnout, averaging over 80 instances per year, with repair costs alone exceeding 2 million yuan. Of these, 77% were caused by poor maintenance (such as water ingress into the motor, insufficient bearing lubrication, and poor ventilation), improper repair (such as improper bearing disassembly and assembly, incomplete defect elimination, and incomplete accessories), substandard machining precision (such as insufficient machining precision after welding of the shaft, and excessive interference fit of the end cap), and harsh operating environment (such as severe leaks and spills on-site, and water-flushing of the motor). It is hoped that the above analysis will be helpful and informative for those working in electrical engineering. Appendix: Common Faults and Troubleshooting Methods for Three-Phase Asynchronous Motors [table=98%][tr][td=1,1,36]Serial Number[/td][td=1,1,144]Fault Phenomenon[/td][td=1,1,216]Fault Cause[/td][td=1,1,252]Troubleshooting Method[/td][/tr][tr][td=1,1,36]1[/td][td=1,1,144]The motor cannot rotate after power is applied, but there is no abnormal noise, odor, or smoke.[/td][td=1,1,216]1. Power supply is not connected (at least two phases are not connected); 2. Fuse is blown (at least two phases are blown); 3. Wiring error in control equipment; 4. The motor is damaged.[/td][td=1,1,252]1. Check the power circuit switch, fuses, and junction box for any breaks and repair them; 2. 1. Check the fuse type and cause of failure, and replace the fuse; 2. Check the motor and repair it. The motor does not turn after power is applied, and then the fuse blows. 1. One phase of power supply is missing, or one stator coil is reverse-connected; 2. Stator winding phase-to-phase short circuit; 3. Stator winding grounded; 4. Stator winding wiring error; 5. Fuse cross-section is too small; 6. Power line short circuit or grounding. 1. Check if one phase of the disconnect switch is not properly closed, or if one phase of the power circuit is broken; eliminate reverse connection faults; 2. Locate the short circuit point and repair it; 3. Eliminate grounding; 4. Locate the incorrect connection and correct it; 5. Replace the fuse; 6. Eliminate grounding points. [td=1,1,36]3[/td][td=1,1,144]The motor does not turn after power is applied, but makes a humming sound.[/td][td=1,1,216]1. There is an open circuit in the stator or rotor windings (one phase is broken) or one phase of the power supply is lost; 2. The winding leads are connected incorrectly at the beginning and end or the winding internal connections are reversed; 3. The power circuit contacts are loose, resulting in high contact resistance; 4. The motor is overloaded or the rotor is stuck; 5. The power supply voltage is too low; 6. The small motor is assembled too tightly or the grease in the bearing is too hard, causing the bearing to stick.[/td][td=1,1,252]1. Locate the break point and repair it; 2. Check the winding polarity; determine if the winding start and end are correct; 3. Tighten loose wiring bolts, use a multimeter to determine if each connection is falsely connected, and repair it; 4. 5. Check if the specified delta connection is mistakenly connected as a Y connection; check if the voltage drop is too large due to the power supply wire being too thin, and correct it; 6. Reassemble to make it flexible; replace with qualified grease and repair the bearings. [/td][/tr][tr][td=1,1,36]4[/td][td=1,1,144]The motor is difficult to start, and the motor speed is often lower than the rated speed when under rated load. [/td][td=1,1,216]1. The power supply voltage is too low; 2. The delta connection is mistakenly connected as a Y connection; 3. The squirrel cage rotor is unwelded or broken; 4. The stator and rotor coils are partially misconnected or reversed; 5. The motor is overloaded. [/td][td=1,1,252]1. Measure the power supply voltage and try to improve it; 2. Correct the connection; 3. Check for unwelded and broken points and repair them; 4. 5. Reduce load. The motor's no-load current is unbalanced, with a large difference between the three phases. 1. Incorrect winding connection; 2. Unbalanced power supply voltage; 3. Winding faults such as inter-turn short circuit or reverse coil connection. 1. Check and correct; 2. Measure power supply voltage and try to eliminate the imbalance; 3. Eliminate winding faults. The motor's no-load current is balanced, but the value is high. 1. Power supply voltage is too high; 2. 1. A Y-connected motor is mistakenly connected as a Δ-connection; 2. The air gap is too large or uneven. 3. Check the power supply and try to restore the rated voltage; 4. Change the connection to a Y-connection; 5. Replace the rotor or adjust the air gap. 6. The motor makes abnormal noises during operation. 7. The motor makes abnormal noises during operation. 8. The stator and rotor insulation is low or the slot wedges rub against each other; 9. The bearings are worn or there are foreign objects such as sand in the oil; 10. The stator or rotor core is loose; 11. The bearings are short of oil; 12. The air duct is blocked or the fan is rubbing against the shroud; 13. The stator and rotor cores rub against each other; 14. The power supply voltage is too high or unbalanced; 15. The stator windings are incorrectly connected or short-circuited. [td=1,1,252]1. Trim insulation and reduce slot wedges; 2. Replace or clean bearings; 3. Inspect stator and rotor cores; 4. Lubricate; 5. Clean air ducts and reinstall fan covers; 6. Remove scratches, and machine a smaller rotor if necessary; 7. Check and adjust power supply voltage; 8. Eliminate stator winding faults.[/td][/tr][tr][td=1,1,36]8[/td][td=1,1,144]Excessive motor vibration during operation.[/td][td=1,1,216]1. Excessive bearing clearance due to wear; 2. Uneven air gap; 3. Rotor imbalance; 4. Bent shaft; 5. Deformed or loose core; 6. Unaligned coupling (pulley); 7. Unbalanced fan; 8. Insufficient strength of casing or foundation; 9. 10. Loose motor foundation bolts; 11. Open circuit, broken circuit, or broken rotor winding in the squirrel cage rotor; 12. Stator winding fault. [td=1,1,252]1. Inspect the bearings and replace them if necessary; 2. Adjust the air gap to make it uniform; 3. Correct the rotor dynamic balance; 4. Straighten the shaft; 5. Correct the overlapping core; 6. Recalibrate to meet specifications; 7. Inspect the fan, correct its balance and geometry; 8. Reinforce; 9. Tighten the foundation bolts; 10. Repair the rotor winding; 11. Repair the stator winding. [td=1,1,36]9[/td][td=1,1,144]Bearing overheating. [td=1,1,216]1. Too much or too little grease; 2. 1. Poor oil quality containing impurities; 2. Improper fit between bearing and journal or end cover; 3. Eccentric bearing cover inner hole causing friction with shaft; 4. Unaligned coupling between motor and load, or excessively tight belt; 5. Excessive or insufficient bearing clearance; 6. Bent motor shaft. [td=1,1,252]1. Add lubricating grease as specified (one-third to two-thirds of volume); 2. Replace with clean lubricating grease; 3. If too loose, repair with adhesive; 4. Repair bearing cover to eliminate rubbing points; 5. Reassemble; 6. Realign and adjust belt tension; 7. Replace with new bearing; 8. Straighten motor shaft or replace rotor. [td=1,1,36]1010[/td][td=1,1,144]Motor overheating or even smoking. [td=1,1,216]1. 1. The power supply voltage is too high, greatly increasing the heating of the iron core; 2. The power supply voltage is too low, and the motor is running under rated load, resulting in excessive current and overheating of the windings; 3. Stator and rotor iron cores rub against each other, causing the motor to overload or start frequently; 4. Broken bars in the squirrel-cage rotor; 5. One phase missing in the motor, operating on two phases; 6. High ambient temperature, excessive dirt on the motor surface, or blocked ventilation ducts; 7. Motor fan failure, poor ventilation; 8. Stator winding fault (phase-to-phase, turn-to-turn short circuit; incorrect internal connection of the stator winding). [td=1,1,252]1. Reduce the power supply voltage (e.g., adjust the tap of the power supply transformer). If the problem is caused by incorrect Y or Δ connection of the motor, the connection should be corrected. 2. Increase the power supply voltage or change the phase power supply wires; 3. Eliminate rubbing points (adjust the air gap or file/machine the rotor), reduce the load, and control the starting according to the specified number of times; 4. Check and eliminate rotor winding faults; 5. Restore three-phase operation; 6. 7. Clean the motor, improve the ambient temperature, and take cooling measures; 8. Inspect and repair the fan, replacing it if necessary; 9. Inspect the stator windings and eliminate faults.