Abstract: Motors are widely used in our region, covering every corner of all walks of life.
It plays an extremely important role in the process of production and life. However, due to the long service life of most motors, power
Machine burning accidents often occur and show an upward trend, which seriously affects the safety and guarantee of production and life.
Depend on, long-term operation. This paper analyzes and studies the causes of motor burning and the corresponding countermeasures.
Keywords: motor motor start-up failure
1 causes and countermeasures of local burning of motor windings
1. 1 Due to the poor seal of the motor itself, the environment leaked and the motor entered.
Water or other corrosive liquids or gases will corrode the insulation of motor windings, which is the most serious.
Short circuit to ground, phase-to-phase short circuit or turn-to-turn short circuit occurs at the weakest point of heavy parts or insulation, and from
Resulting in local burning of the motor winding.
Corresponding countermeasures: ① try to eliminate the leakage of process and mechanical equipment; ② Maintenance.
Pay attention to the sealing of all parts of the motor, for example, apply a small amount of 704 seal to each flange.
Glue and grease bolts. If necessary, install drip-proof boxes, such as motors, in junction boxes and other places.
Be well protected when exposed to places that are easy to invade liquids and dirt; ③ Yes, running in this environment.
Motor should shorten the period of minor repair and medium repair, and carry out medium repair in time when it is serious.
1.2 Friction between stator and rotor due to bearing damage and shaft bending (commonly known as bore sweeping).
The temperature of the iron core rises sharply, and the slot insulation and turn-to-turn insulation are burnt out, which leads to the separation of winding turns from the surface.
Short circuit or "shoot" to the ground. In severe cases, the stator core will be reversed, dislocated, the rotating shaft will be worn and the end cover will be damaged.
Scrapping, etc. Bearing damage is generally caused by the following reasons: ① improper assembly of bearings, such as cold assembly.
Uneven knocking of bearing inner ring leads to shaft wear, which leads to the loss of fit between bearing inner ring and bearing.
The interference amount or the interference amount is smaller, which leads to the phenomenon of inner ring running, and the guide rail hits unevenly when installing the motor end cover.
The loose fit between the bearing chamber of the end cover and the bearing outer ring leads to the deviation of the outer ring. Whether to run the inner loop
Even if the outer ring runs, the bearing temperature will rise sharply and burn, especially the inner ring.
Failure will lead to serious wear and bending of the rotating shaft. But this is not usually the case when the outer ring is operated intermittently.
Lead to a sharp rise in bearing temperature, as long as the bearing is in good condition, the phenomenon of intermittent running of the outer ring is allowed.
Yes ② The bearing cavity is not cleaned or the added grease is not clean. Such as in a bearing housing.
Small rigid materials are not completely cleaned, and the bearing raceway is damaged during operation, resulting in excessive temperature rise.
Burn the bearing. (3) Bearing replacement treatment, interference or ellipticity appears after motor end cover nesting.
The bearing ball clearance is too large, too small or uneven, which leads to the increase of friction when the bearing is running.
The temperature rises sharply until it burns. (4) Due to axial dislocation of stator and rotor cores or realignment of rotating shafts.
After machining, the accuracy is not enough, so that the inner and outer rings of the bearing are not on the same tangent plane, resulting in bearing transportation.
After eating "turtle essence", the temperature rises until it burns. ⑤ Because the temperature rise of motor body and shaft is too high.
Bearings are short of oil or even burned because they are not lubricated in time. ⑥ Due to different types of grease
Mixed use will lead to bearing damage. ⑦ The bearing itself has manufacturing quality problems, such as raceway rust,
Flexible rotation, excessive clearance, cage deformation, etc. ⑧ If the standby machine does not run for a long time, the grease will change.
Quality, bearing rust without intermediate repair.
Countermeasures: ① When disassembling the bearing, the bearing should be heated to 80℃~ 100℃,
If bearing heaters and transformer oil boilers are used, only in this way can bearing assembly be ensured.
Quality. (2) Before installing the bearing, it must be carefully cleaned, and no bearing cavity can be left.
If there are impurities, be sure to keep them clean when adding grease. ③ Try to avoid unnecessary rotating shaft machines.
Machining and motor end cover nesting work. (4) When assembling the motor, make sure that the stator and rotor cores are aligned.
, shall not be misplaced. (5) The motor shell shall be clean, the ventilation shall be ensured, and the cooling device shall not.
There may be dirt, and the blades should be kept intact. 6. It is forbidden to mix all kinds of lubricating grease. ⑦ Install the bearing.
Before loading, it is necessary to conduct a comprehensive and careful integrity check. ⑧ For motors that are not used for a long time,
Before use, necessary disassembly inspection must be carried out to update the bearing grease.
1.3 The end cover or other accessories are worn due to the winding end being too long or partially damaged.
Friction, resulting in local winding burning out.
Corresponding countermeasures: when the motor winding is updated, the wires must be embedded according to the original data. When overhauling the motor
No rigid objects are allowed to touch the winding. When the motor rotor pulls the core, the rotor must be lifted to prevent the stator and rotor core from rubbing against each other. When using an open flame, the winding must be isolated from the open flame and guaranteed.
There is a certain distance. Before reassembling the motor, carefully check the integrity of the winding.
Confirmed.
1.4 due to long-term overload or overheating operation, winding insulation aging is accelerated, and insulation is the most
The phenomenon of turn-to-turn short circuit, phase-to-phase short circuit or short circuit to ground caused by weak carbonization makes the winding local
The department burned down.
Corresponding countermeasures: ① Try to avoid motor overload operation. ② Ensure that the motors are clean and connected in parallel.
The wind dissipates heat well. ③ Avoid frequent starting of the motor, and dynamically balance the motor rotor when necessary.
Experiment.
1.5 motor winding insulation is affected by mechanical vibration (e.g., large current impact during starting, caused by dragging).
For vibration, motor rotor imbalance, etc. ), make the winding turn-to-turn relaxation, insulation cracks, etc.
Bad phenomena and destructive effects are accumulating, and the winding rubs due to thermal expansion and cold contraction, thus accelerating.
In order to avoid insulation aging, it will eventually lead to the first carbonization insulation damage until the winding is burned.
Countermeasures: ① Try to avoid frequent starting, especially for high-voltage motors. 2 guarantee to become
The vibration values of the dragging equipment and motor are within the specified range.
2 Three-phase asynchronous motor one or two-phase winding burning (or overheating) causes and countermeasures
If the single-phase or two-phase winding of the motor is burnt out (or overheated), it is generally because.
Caused by open-phase operation. No matter what causes the motor to be out of phase, the motor can continue to run.
Ok, but the speed decreases and the slip becomes larger, in which B and C are connected in series and then merged with A.
Under the condition of constant load, a certain phase current is too large, and the phase winding is inevitable after long-term operation.
Overheating and burning.
The winding of three-phase asynchronous motor is Y-shaped: after the power supply is out of phase, the motor
It can continue to run, but the same speed is obviously reduced, the slip rate is increased, and the speed of magnetic field cutting conductor is increased.
When the speed increases, the phase B winding is disconnected, and the phase A and phase C windings are connected in series and pass through.
Excessive current and long-term operation will cause two-phase windings to burn out at the same time.
Under special circumstances, if the stopped motor is short of one-phase power supply for closing, it will only be sent.
Hum, can't start, this is because the motor is connected with symmetrical three-phase alternating current.
A circular rotating magnetic field is generated in the stator core, but when the phase power supply is lacking, a circular rotating magnetic field is generated in the stator core.
The purpose is single-phase pulsating magnetic field, which can not make the motor produce starting torque. Therefore, the power supply is out of phase.
When the motor cannot be started. However, in operation, three-phase harmonics will be generated in the air gap of the motor.
It has a high elliptical rotating magnetic field, so the running motor can still transport after it is out of phase.
Turn is only the distortion of magnetic field, and the harmful current component increases sharply, which eventually leads to the winding burning out.
Corresponding countermeasures: No matter whether the motor is static or dynamic, the lack of phase operation brings direct
The harm is that the single-phase or two-phase winding of the motor is overheated or even burned out. At the same time, due to electricity
Overcurrent operation of cable accelerates insulation aging. Especially in the static state, the missing phase will be in the motor winding.
Produce a locked-rotor current that is several times the rated current. The burning speed of its winding is faster than that in operation.
But lack of phase is faster and more serious. So when we carry out routine maintenance and overhaul of the motor,
The corresponding MCC functional unit of the motor must be thoroughly overhauled and tested. special
The reliability of load switch, power supply circuit and static and dynamic contacts must be carefully checked. Put an end to open-phase operation.
In a word, both electrical workers and managers should proceed from reality.
Effectively implement equipment maintenance and repair, ensure the normal operation of production, and promote
Economic construction has developed smoothly.