Ten causes of Motor Vibration
1. Rotor, coupling, coupling, transmission wheel (brake wheel) caused by the imbalance.
2. Core support loose, oblique key, pin failure loose, rotor tie not tight will cause part of the rotation imbalance.
3. Linkage part of the shafting misalignment, Central Line does not coincide, centering is not correct. The main cause of this failure is the installation process, malalignment, improper installation.
4. The Central Line of linkage part is coincident in the cold state, but after running for a period of time, because of the deformation of Rotor Fulcrum, foundation and so on, the Central Line is destroyed, so the vibration is produced.
5. The gears and couplings connected with the motor are malfunctioning, the gears are not properly engaged, the teeth of the gears are badly worn, the wheels are badly lubricated, the couplings are askew and out of place, the teeth of the gear couplings are not in the right shape, the teeth spacing is not correct, the clearance is too large or the wear is serious, creates a certain amount of vibration.
6. The structural defects of the motor itself, the ellipse of the shaft neck, the bending of the rotating shaft, the too large or too small clearance between the shaft and the bearing Bush, the rigidity of the bearing seat, the foundation plate, some part of the foundation and even the whole installation foundation of the motor is not enough. Kill.
7.Installation problems, the motor and the foundation plate between the fixed is not solid, the foot bolts loose, loose between the bearing block and the foundation plate, etc. .
8. Too Large or too small clearance between bearing and Bush can not only cause vibration but also cause abnormal lubrication and temperature of Bush.
9. Motor-driven load conduction vibration, such as motor-driven Fan, water pump vibration, resulting in motor vibration.
10. AC Motor stator wiring error, winding type asynchronous Motor Rotor winding short circuit, Synchronous Motor Excitation Winding Inter turn short circuit, synchronous motor excitation coil connection error, cage type asynchronous motor rotor broken bar, the air gap of stator and rotor is uneven due to the deformation of rotor core, which leads to the unbalance of air gap flux and vibration. The vibration of electric motor will shorten the life of winding insulation and bearing, affect the normal lubrication of sliding bearing, and the vibration force will enlarge the insulation gap and cause the outside dust and water to invade into it, it causes the decrease of insulation resistance and the increase of leakage current, and even causes insulation breakdown and other accidents. In addition, the vibration produced by the electric motor can easily cause the water pipe of the cooler to crack and the welding point to open, at the same time, it can cause the mechanical damage of the load, reduce the precision of the work piece, and cause the fatigue of all the mechanical parts that are subjected to vibration, it will make the foundation screw loose or break, the motor will cause the abnormal wear of the carbon brush and the slip ring, even there will be serious brush fire and burn the insulation of the collector ring, the motor will produce a lot of noise, this kind of situation also often occurs in the direct current motor.
The causes of vibration and typical cases of vibration are mainly three cases: electromagnetic reasons; mechanical reasons; electromechanical reasons.
1, electromagnetic reasons (1) power: three-phase voltage imbalance, three-phase motor phase operation. (2) for the stator, the core of the stator is oval, eccentric and loose, the stator windings are broken, ground broken, inter-turn short circuit, wiring error, and the three-phase current of the stator is unbalanced. EXAMPLE: the Boiler Room Seal Fan Motor repair found before the stator core has red powder, suspected stator core loose phenomenon, but not within the scope of the standard overhaul of the project, so did not deal with, after the overhaul, the electrical machinery occurs the ear-piercing scream, after the replacement of a stator troubleshooting. (3) Rotor Fault: the core of the rotor becomes elliptical, eccentric and loose. Rotor Cage Bar and end ring open welding, rotor cage bar broken, wire winding error, poor brush contact and so on. For example: during the operation of saw motor without teeth in sleeper section, it was found that the motor stator current oscillated back and forth, and the motor vibration increased gradually, there are 7 breaks in the rotor cage bars, and the two serious side and end rings have all been broken. If it is not found in time, it may cause the bad accident of stator burning.
2, mechanical reasons (1) motor itself: Rotor Imbalance, Shaft Bending, Slip Ring Deformation, air gap imbalance between stator and rotor, magnetic center inconsistency between stator and Rotor, bearing failure, poor foundation installation, Mechanical Structure Strength Insufficient, resonance, loose foundation screw, damaged motor and fan. Typical case: After the factory condensate pump motor replaced the upper bearing, the motor sloshing increased, and the rotor and stator have slight signs of scanning bore. After careful inspection, it was found that the rotor lifting height of the motor was not correct, and the rotor and stator magnetic center were not aligned, the vibration fault of the motor is eliminated after adjusting the spare cap of the thrust head screw. After repair, the vibration of the lifting coil motor has been on the high side, and there are signs of gradual increase. When the motor dropped its hook, it was found that the vibration of the motor was still very large, and there was a large series of axial movements. It was found that the rotor core was loosened after disassembly, rotor balance is also a problem, replacement of spare rotor after the fault is eliminated, the original rotor repair factory. (2) with respect to coupling: coupling damage, coupling connection is not good, coupling to find the center is not accurate, load mechanical imbalance, system resonance. Linkage part of the shafting misalignment, Central Line does not coincide, centering is not correct. The main cause of this failure is the installation process, malalignment, improper installation. There is also a case, that is, some linkage part of the central line is coincident in the cold state, but after running for a period of time because of the Rotor Fulcrum, foundation deformation, the central line is destroyed, resulting in vibration. A, circulating water pump motor, running vibration has been on the high side, motor check without any problem, no load is also all normal, pump class think motor operation is normal, finally check out motor find center is too much, pump class from new find right, elimination of motor vibration. B, after replacing the belt pulley of the induced draft fan in the boiler room, the motor vibrates during the trial operation and the three-phase current of the motor increases at the same time. After checking all the circuits and electrical components without any problems, it is found that the belt pulley is not up to standard and the motor vibration is eliminated after the replacement, at the same time, the three-phase current of the motor is also back to normal.
3, Motor Mixing Reason (1) motor vibration is often air gap uneven, causing unilateral electromagnetic pull, and unilateral electromagnetic pull and further increase the air gap, this kind of mechanical-electrical mixing performance for motor vibration. (2) the axial series movement of the motor causes the axial series movement of the motor due to the electromagnetic pulling force caused by the gravity of the rotor itself or the installation level and the incorrect magnetic force center, which causes the vibration of the motor to increase, and in serious cases, the bearing is ground, causes the bearing Bush temperature to rise rapidly. There is something wrong with the gears and couplings connected with the motor. This kind of trouble mainly displays for the gear to bite bad, the gear tooth attrition is serious, to the wheel lubrication bad, the coupling is askew, the dislocation, the gear type coupling tooth shape, the tooth distance is wrong, the clearance is too big or the attrition is serious, will cause the certain vibration. (4) defects in the structure of the motor itself and problems in its installation. This kind of fault mainly displays for the axle journal Ellipse, the rotating axle is bent, the gap between the axle and the axle Bush is too big or too small, the rigidity of the bearing base, the foundation plate, some part of the foundation or even the whole motor installation foundation is not enough, the motor and the foundation plate are not fixed firmly, the base bolt is loose, the bearing seat and the foundation plate are loose. But the clearance between the axle and the bearing Bush is too big or too small not only can cause the vibration but also can cause the bearing Bush lubrication and the temperature to produce the unusual. (5) the load driven by the motor conducts the vibration. For example: TURBO-GENERATOR TURBINE VIBRATION, motor-driven fan, water pump vibration, resulting in motor vibration.
How to find out the cause of vibration in order to eliminate the vibration of motor, the first thing to do is to find out the cause of vibration, only to find out the cause of vibration, can take targeted measures to eliminate motor vibration. 1. Before the motor is shut down, check the vibration of each part with the vibration meter. For the parts with larger vibration, test the vibration value in three directions of vertical and horizontal axis in detail. If the foundation screw is loose or the end cover screw is loose, then it can be fixed directly, and the vibration of the motor can be measured after fastening to observe whether it has been eliminated or reduced. Secondly, it is necessary to check whether the three-phase voltage of the power supply is balanced and whether the three-phase fuse has been burnt out.