There are many and complex reasons for the vibration of explosion proof low voltage motor. explosion proof low voltage motors with more than 8 poles will not cause vibration due to manufacturing quality issues of explosion proof low voltage motors. Vibration is commonly found in 2-6 pole explosion proof low voltage motors, GB10068-2000. "Vibration Limits and Test Methods for Rotating explosion proof low voltage Motors" stipulates the vibration limits, measurement methods, and determination criteria for rigid foundations of explosion proof low voltage motors with different center heights on a rigid foundation. According to this standard, it can be determined whether the explosion proof low voltage motor complies with the standard.
The hazards of motor vibration
Vibration in an electric motor can shorten the insulation of windings and the lifespan of bearings, affect the normal lubrication of sliding bearings, and the vibration force will cause the insulation gap to expand, allowing external dust and moisture to invade, resulting in a decrease in insulation resistance and an increase in leakage current, and even lead to insulation breakdown and other accidents. In addition, the vibration generated by the motor can easily cause the water pipes of the cooler to crack, the welding points to open up, and at the same time, it will cause damage to the load machinery, reduce the accuracy of the workpiece, cause fatigue in all the mechanical parts affected by vibration, loosen or break the anchor bolts, and cause abnormal wear of the carbon brushes and slip rings of the motor. In severe cases, it may even lead to severe brush fire and burn out the insulation of the collector ring. The motor will generate a lot of noise, and this situation usually occurs from time to time in DC explosion proof low voltage motors.
Ten reasons for motor vibration
It is caused by the imbalance of the rotor, coupler, coupling and drive wheel (brake wheel).
2. Loose core supports, failed or loose inclined keys and pins, and loose rotor binding can all cause imbalance in the rotating parts.
3. The shaft system of the interlocking part is misaligned, the centerlines do not coincide, and the centering is incorrect. The main cause of this kind of malfunction is poor alignment and improper installation during the installation process.
4. The centerlines of the interlocking parts are consistent in the cold state, but after running for a period of time, due to the deformation of the rotor support points, foundation, etc., the centerlines are damaged again, thus causing vibration.
5. Faults in the gears and couplings associated with explosion proof low voltage motor, such as poor gear meshing, severe tooth wear, poor lubrication of the mating wheels, skewed or misaligned couplings, incorrect tooth shape and pitch, excessive clearance or severe wear of the gear couplings, will all cause certain vibrations.
6. Defects in the structure of the explosion proof low voltage motor itself: The journal is elliptical, the rotating shaft is bent, and the clearance between the shaft and the bearing bush is too large or too small The stiffness of the bearing housing, the base plate, a certain part of the foundation, or even the entire explosion proof low voltage motor installation foundation is insufficient.
7. Installation issues: The explosion proof low voltage motor is not firmly fixed to the base plate, the anchor bolts are loose, and the bearing housing is loose to the base plate, etc.
Excessive or insufficient clearance between the shaft and the bearing bush can not only cause vibration but also lead to abnormal lubrication and temperature of the bearing bush.
9. The load driven by explosion proof low voltage motor conducts vibration, such as the vibration of fans and water pumps driven by explosion proof low voltage motor. Cause explosion proof low voltage motor to vibrate.
10. Stator wiring error of AC explosion proof low voltage motor, short circuit of rotor winding of wound-rotor asynchronous motor, inter-turn short circuit of excitation winding of synchronous explosion proof low voltage motor The excitation coil connection of the synchronous explosion proof low voltage motor is incorrect. The rotor bars of the squirrel-cage asynchronous motor are broken. The deformation of the rotor core causes uneven air gaps between the stator and rotor, resulting in unbalanced magnetic flux in the air gap and thus causing vibration.
Vibration causes and typical cases
There are mainly three causes of vibration: electromagnetic reasons; Mechanical reasons; The reasons are related to the electromechanical hybrid aspect.
I. Reasons related to electromagnetism
1. Power supply aspect: Unbalanced three-phase voltage, three-phase motor running with a missing phase.
2. Stator aspect: The stator core becomes elliptical (official account: Pump Manager), eccentric, loose; The stator winding experiences broken wires, ground breakdown, inter-turn short circuits, incorrect wiring, and unbalanced three-phase currents of the stator.
For example: Before the maintenance of the explosion proof low voltage motor sealed fan in the boiler room, red powder was found in the stator core, and it was suspected that the stator core was loose. However, it was not within the scope of the standard major overhaul, so it was not dealt with. After the major overhaul, during the trial run of the explosion proof low voltage motor, a shrill screeking occurred. The fault was eliminated after replacing one stator.
3. Rotor failure: The rotor core becomes elliptical, eccentric, or loose. The rotor cage bars are unwelded to the end rings, the rotor cage bars are broken, the winding is incorrect, and the brush contact is poor, etc.
For example: During the operation of the toothless saw explosion proof low voltage motor in the sleeper section, it was found that the stator current of the explosion proof low voltage motor was swinging back and forth. The vibration of the explosion proof low voltage motor is gradually increasing. Judging from the phenomenon, there is a possibility that the rotor cage bars of the explosion proof low voltage motor may have weld opening and breakage. After disassembling the explosion proof low voltage motor, it was found that there were 7 breaks in the rotor cage bars. The two severe ones had completely broken both sides and end rings. If not discovered in time, it may cause a serious accident of stator burnout.
Ii. Mechanical reasons
1.explosion proof low voltage motor itself:
Rotor imbalance, shaft bending, slip ring deformation, uneven air gap between stator and rotor, inconsistent magnetic center of stator and rotor, bearing failure, poor foundation installation, insufficient strength of mechanical structure, resonance, loose anchor bolts, explosion proof low voltage motor fan damage.
Typical case After the upper bearing of the factory condensate pump explosion proof low voltage motor was replaced, the motor's shaking increased, and there were slight signs of the rotor and stator scraping. After a careful inspection, it was found that The rotor lifting height of the explosion proof low voltage motor was incorrect, and the magnetic centers of the rotor and stator were not aligned. After readjusting the thrust head screw cap, the vibration fault of the explosion proof low voltage motor was eliminated. The vibration of the explosion proof low voltage motor lifted by the cross-line hoist ring has been relatively large since the maintenance, and there is a sign of gradual increase. When the explosion proof low voltage motor fell off the hook, it was found that the vibration of the explosion proof low voltage motor was still very large, and there was a lot of axial movement. After disassembly, it was found that the rotor core was loose and there was also a problem with the rotor balance. After replacing the spare rotor, the fault was eliminated and the original rotor was returned to the factory for repair.
2. Regarding the fit with couplings:
Coupling damage, poor coupling connection, inaccurate alignment of the coupling center, mechanical imbalance of the load, system resonance, etc. The shaft system of the linkage part is not aligned, the centerlines do not coincide, and the centering is incorrect. The main cause of this kind of malfunction is poor alignment and improper installation during the installation process. There is another situation where the centerlines of some interlocking parts are consistent in the cold state, but after running for a period of time, due to the deformation of the rotor support points, foundation, etc., the centerlines are damaged again, thus causing vibration.
For example:
A. The vibration of the circulating water pump explosion proof low voltage motor has been relatively large during operation. There are no problems with the explosion proof low voltage motor upon inspection, and everything is normal even under no-load conditions. The pump team believed that the explosion proof low voltage motor was operating normally. Eventually, it was found that the alignment center of the explosion proof low voltage motor was too different. After the pump team re-aligned it, explosion proof low voltage motor Vibration Elimination.
After the pulley of the induced draft fan in the boiler room was replaced, vibration occurred during the trial operation of the explosion proof low voltage motor, and the three-phase current of the explosion proof low voltage motor increased simultaneously. After inspecting all circuits and electrical components and finding no problems, it was finally discovered that the pulley was unqualified. After replacement, the vibration of the explosion proof low voltage motor was eliminated, and at the same time, the three-phase current of the explosion proof low voltage motor also returned to normal.
Iii. Reasons for explosion proof low voltage motor Mixing
The vibration of explosion proof low voltage motors is often due to uneven air gaps, which cause unilateral electromagnetic pulling force. This unilateral electromagnetic pulling force further increases the air gap, and this electromechanical hybrid effect is manifested as the vibration of explosion proof low voltage motors.
2. Axial movement of the explosion proof low voltage motor is caused by the electromagnetic pulling force resulting from the rotor's own gravity, installation level, or incorrect magnetic center, leading to axial movement of the explosion proof low voltage motor. It causes an increase in the vibration of the explosion proof low voltage motor. In severe cases, shaft wear occurs at the bearing bush root, causing the temperature of the bearing bush to rise rapidly.
There is something wrong with the gears and couplings associated with explosion proof low voltage motor. This kind of malfunction is mainly manifested as poor gear meshing, severe wear of gear teeth, poor lubrication of the mating wheels, skewing and misalignment of the couplings, incorrect tooth shape and pitch, excessive clearance or severe wear of the gear couplings, all of which will cause certain vibrations.
The structural defects and installation problems of the explosion proof low voltage motor itself. This kind of fault is mainly manifested as an elliptical journal, bending of the rotating shaft, excessive or insufficient clearance between the shaft and the bearing bush, insufficient rigidity of the bearing housing, base plate, a certain part of the foundation or even the entire explosion proof low voltage motor installation foundation, The explosion proof low voltage motor is not firmly fixed to the base plate, the anchor bolts are loose, and the bearing housing is loose to the base plate, etc. Excessive or insufficient clearance between the shaft and the bearing bush can not only cause vibration but also lead to abnormal lubrication and temperature of the bearing bush.
The load driven by explosion proof low voltage motor conducts vibration.
For example: The steam turbine of explosion proof low voltage motor vibrates, and the fans and pumps driven by explosion proof low voltage motor vibrate. Cause explosion proof low voltage motor to vibrate.
How to find out the cause of vibration?
To eliminate the vibration of an electric motor, it is first necessary to identify the cause of the vibration. Only by finding the cause of the vibration can targeted measures be taken to eliminate it.
Before the motor stops, use a vibration meter to check the vibration conditions of all parts. For parts with significant vibration, test the vibration values in detail in the vertical, horizontal and axial directions. If the anchor bolts or bearing end cover screws are loose, they can be directly tightened. After tightening, measure the vibration size again and observe whether it has been eliminated or reduced. Secondly, check whether the three-phase voltage of the power supply is balanced Check if the three-phase fuse has burned out. The single-phase operation of the motor can not only cause vibration but also make the temperature of the explosion proof low voltage motor rise rapidly. Observe whether the pointer of the ammeter swings back and forth. When the rotor bar breaks, the current swings. Finally, check whether the three-phase current of the explosion proof low voltage motor is balanced. If any problem is found, contact the operating personnel in time to stop the operation of the explosion proof low voltage motor. So as not to burn out the explosion proof low voltage motor.
2. If the vibration of the explosion proof low voltage motor is not resolved after the surface phenomenon is treated, continue to disconnect the power supply, loosen the coupling, and mechanically separate the explosion proof low voltage motor from the connected load. Single-rotation explosion proof low voltage motor. If the explosion proof low voltage motor itself does not vibrate, it indicates that the vibration source is caused by misaligned couplings or mechanical loads If the explosion proof low voltage motor vibrates, it indicates that there is a problem with the explosion proof low voltage motor itself. Additionally, the power-off method can be adopted to distinguish whether it is an electrical cause.
explosion proof low voltage motor https://www.juyueenergy.com/Low-voltage-motor
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