The motor has the characteristics of simple structure, reliable operation, convenient use and low price. In order to ensure the normal operation of Opportunity, the running motor should be inspected according to the requirements of motor integrity quality standards, the axis of the running motor and the towed equipment should be aligned, there should be no obvious vibration during operation, and good ventilation and wings should be kept intact. The voltage and normal working current of the motor network must be observed and measured at any time. The voltage change should not exceed 5% of the rated voltage, and the rated load current of the motor should not always exceed the rated current to prevent overheating. At the same time, check whether the motor starting protection device is flexible and reliable. Check whether the temperature rise of all parts of the motor is normal, and also check the bearing temperature frequently. Sliding bearings shall not exceed 70 degrees, and rolling bearings shall not exceed 70 degrees. The sound of rolling bearing during operation should be clear and noiseless. For the operating environment of the motor, it is necessary to prevent smashing, rain and moisture. For those with harsh environment, those with frequent moving, frequent startup and overload operation, it is necessary to strengthen daily maintenance and find and eliminate hidden dangers in time.
I. Analysis and Treatment of Common Electrical Faults of Motors
(a) After the turn-on time, the motor cannot be started, but there is a buzz.
Possible reasons: (1) The power supply is not fully connected to start the single phase; (2) Motor overload; (3) being stuck by the tractor; (4) The rotor circuit of the wound motor is open or broken; (5) The position of the inner head end of the stator is wrong, or there is a broken line or short circuit.
Treatment: (1) Check each pair of contacts of power cord, motor lead-out, fuse and switch, find out the broken position and eliminate it; (2) No-load or half-load starting after unloading; (3) Check the towed machinery and troubleshoot it; (4) Check the engagement of each contactor of the brush, slip ring and starting resistor; (5) Re-judge the beginning and end of the three-phase and check whether there are bright wires and short circuits in the three-phase winding.
(2) The motor is difficult to start, and the rotation speed is low after the rated load is added.
Possible reasons: (1) Low power supply voltage; (2) It turned out that the angle joint was staggered and became a star joint; (3) The cage bar end of squirrel-cage rotor is off-welded, loose or broken.
Treatment: (1) increase the voltage; (2) Check the wiring mode of the nameplate and correct the wiring mode of the stator winding; (3) After inspection and symptomatic treatment.
(three) after the motor starts, it heats up more than the temperature rise standard or smokes.
Possible reasons: (1) The power supply voltage is too low, and the motor temperature rise is too high under rated load; (2) The motor is poorly ventilated or the ambient humidity is too high; (3) motor overload or single-phase operation; (4) The motor is frequently started or reversed too many times; (5) The stator and rotor rub against each other.
Treatment method: (1) measure no-load and load voltage; (2) Check the motor fan, clean the ventilation pipe, strengthen ventilation and reduce the ambient temperature; (3) After checking each phase current with a clamp ammeter, treat it symptomatically; (4) Reduce the number of positive and negative rotations of the motor, or replace the motor suitable for frequent starting and positive and negative rotation; (5) Treatment of menstrual illness after examination.
Low insulation resistance
Possible reasons: (1) The winding is wet or dripped into the motor; (2) There is dust and grease on the winding; (3) Insulation aging of stator winding.
Treatment method: (1) heat and dry the stator and rotor windings; (2) scrubbing the winding end with gasoline and drying; (3) Check and restore the outgoing line insulation or replace the insulation board of the junction box; (4) In general, all windings need to be replaced.
(5) The motor shell is charged:
Possible reasons: (1) insulation of motor lead-out wire or insulation board of junction box; (2) the winding end contacts the bushing; (3) The motor housing is not reliably grounded.
Treatment: (1) Restore the insulation of the motor lead or replace the insulation board of the junction box; (2) If the grounding phenomenon disappears after the end cover is removed, the end cover can be installed after the winding end is insulated; (3) The motor shell shall be reliably grounded according to the grounding requirements.
(6) Abnormal sound when the motor is running.
Possible reasons: (1) Wrong connection of stator winding, local short circuit or grounding, resulting in unbalanced three-phase current and noise; (2) There are foreign bodies in the bearing or there is a serious shortage of lubricating oil.
Treatment: (1) Check separately and prescribe the right medicine; (2) After cleaning the bearing, replace it with new lubricating oil with 1/2- 1/3 in the bearing chamber.
(7) Motor vibration
Possible reasons: (1) uneven motor installation foundation; (2) the motor rotor is unbalanced; (3) The pulley or coupling is unbalanced; (4) The shaft head of the rotating shaft is bent or the pulley is eccentric; (5) The motor fan is unbalanced.
Treatment method: (1) level the motor base and fix it when the time is ripe; (2) Static or dynamic balance of the rotor; (3) balancing the pulley or coupling; (4) straighten the rotating shaft, align the pulley, and then insert it into the sleeve for re-rotation; (5) Static fan.
Second, the analysis and treatment of common motor faults
(A) stator and rotor core fault maintenance
Stator and rotor are made of mutually insulated silicon steel sheets, which are the magnetic circuit parts of the motor. Damage and deformation of stator and rotor cores are mainly caused by the following reasons.
(1) Excessive wear or poor assembly of bearings will cause the stator and rotor to rub against each other and damage the surface of the iron core, which will lead to short circuit between silicon steel sheets, increase the iron loss of the motor, and make the temperature rise of the motor too high. At this time, tools such as a fine file should be used to remove burrs, eliminate short circuits of silicon steel sheets, clean them, coat them with insulating paint, and heat and dry them.
(2) When dismantling the old winding, the force is too large, so that the inverted slot is skewed and opened outward. At this time, tools such as small pliers and wooden hammer should be used for trimming to reset the cogging, and hard insulating materials such as green paper and bakelite should be added between silicon steel sheets with gaps that are not easy to reset.
(3) The iron core surface rusts due to moisture and other reasons. At this time, it needs to be polished with sandpaper and coated with insulating paint after cleaning.
(4) The high temperature caused by winding grounding burns the iron core or teeth. You can use tools such as chisel or scraper to remove deposits, coat them with insulating dysprosium and dry them.
(5) The combination of iron core and frame is loose, and the original positioning screw can be tightened. If the positioning screw fails, the positioning hole can be re-drilled on the base, tapped and tightened.
(2) Bearing troubleshooting
The rotating shaft is supported by the bearing, which is the heaviest part and easy to wear.
(1) fault check
Inspection in operation: when the rolling bearing is short of oil, the sound of bone and bone will be heard. If the valve stem is discontinuous, it may be that the bearing steel ring is broken. When the bearing is mixed with sand and other sundries or the bearing parts are slightly worn, it will produce slight noise.
Inspection after disassembly: firstly, check whether the bearing roller and the inner and outer steel rings are damaged, corroded and scarred, then hold the bearing inner ring with one hand and make the bearing smooth, and push the outer steel ring with the other hand. If the bearing is in good condition, the outer steel ring should rotate smoothly, without vibration and obvious jamming, and the outer steel ring will not go backwards after stopping, otherwise the bearing can not be used any more. Grasp the outer ring with the left hand and the inner ring with the right hand, and push hard in all directions. If you feel loose when pushing, it is seriously worn.
(2) Fault repair
Rust spots on the outer surface of the bearing can be wiped off with No.00 sandpaper, and then cleaned with gasoline; Or the bearing is cracked, the inner and outer rings are broken or the bearing is excessively worn, and a new bearing should be replaced. When replacing a new bearing, choose the same bearing as the original model.
(3) Troubleshooting of rotating shaft
(1) axis bending
If the bending is not big, it can be repaired by grinding the shaft diameter and slip ring; If the bending exceeds 0.2 mm, the shaft can be placed under a press, and the bending part can be pressurized and corrected, and the corrected shaft surface can be cut and polished by a lathe; If the bending is too large, a new shaft needs to be replaced.
(2) journal wear
When the wear of important official neck is not great, a layer of chromium can be plated on the journal and then ground to the required size; When there is more wear, surfacing welding can be carried out on the journal, and then cutting and polishing can be carried out on the lathe; If the journal is excessively worn, rotate the journal for 2-3mm, then rotate a sleeve on the journal while it is hot, and then rotate it to the required size.
(3) Shaft crack or fracture
When the depth of transverse cracks in important official does not exceed 10%- 15% of the shaft diameter, and the longitudinal cracks do not exceed 10% of the shaft length, it can be remedied by surfacing welding, and then finished turning to the required size. If the crack of the shaft is serious, it needs to be replaced with a new shaft.
(4) Maintenance of shell and end cover
If the shell and end cover have cracks, they should be repaired by surfacing welding. If the bearing boring clearance is too large, resulting in loose fit of the bearing end cover, generally, a punch can be used to evenly punch the bearing hole wall, and then the bearing can be driven into the end cover. For high-power motors, bearings with the required size can also be finally processed by patching or electroplating.
With the wide use of motors in industrial and mining fields, the timely maintenance and repair of motors have been highly valued by leaders and technicians at all levels. Only by strengthening the daily maintenance and repair of motors can we create more wealth for the society economically and safely.