From the motor itself, the vibration value of the motor is mainly related to the dynamic balance of the rotor.
From the external situation of the motor, the installation quality of the motor and the host machine, the middle situation, the lack of rigidity of the foundation, the natural frequency of the motor and the foundation is close to and so on will also cause the vibration value of the motor to exceed the standard.
Note: When the motor vibration value is qualified in air test and exceeds the limit after loading, the problems outside the motor should be checked first.
(1) Motor bearing reasons.
Some equipment manufacturers in the installation of motor couplings, the use of cold driving method (not the heating coupling after the hot sleeve method), resulting in bearing raceway and cage damage, resulting in motor vibration value exceeds the standard.
Incorrect lifting methods (such as quick landing of the motor and collision of the motor) in the process of user site lifting will also cause damage to the bearing raceway and cage, resulting in excessive vibration value of the motor.
When the motor is placed on the project site for a long time, the injector nozzle and oil pipe are missing, the motor bearing is rusting with water and the grease is deteriorating, all the above factors will cause the motor vibration value to exceed the standard.
(2) Insufficient rigidity of equipment foundation
The rigidity of the common base of the equipment is insufficient, or the concrete foundation under the common base is insufficient, and the vibration value measured after the motor is energized exceeds the standard. In this case, it is necessary to strengthen the foundation to solve the problem of excessive vibration value.
National standard GB10068-2008 "shaft center height of 56mm and above motor mechanical vibration measurement, evaluation limit value" stipulates that the rigid installation should meet the following requirements: The maximum vibration velocity measured on the bottom of the motor (or on the base near the bottom of a seated bearing or stator) in both horizontal and vertical directions shall not exceed 25% of the maximum vibration velocity measured on the adjacent bearing in either horizontal or vertical directions.
(3) The flatness of the base is out of tolerance
The common base plane is uneven, the motor is placed on the base or the motor is tightly on the base, and the vibration value of the motor exceeds the standard after electrification. The vibration value is normal after loosening all or part of the base bolt of the motor, but exceeds the standard when tightening again.
A. When the motor is installed on site, hit the bottom of the motor with a sledgehammer when it is in alignment.
B. When the motor foot is not flat or solid, tighten the motor foot bolt forcefully during installation.
The above conditions will cause deformation of the motor foot, abnormal force of the bearing, and excessive vibration value of the motor after energization.
When the motor base is processed in the factory, it is processed in the milling machine last time, so the motor foot should not be suspected of being uneven when leaving the factory.
When it is found that the motor foot is out of shape (naked eye observation and feeler check, check on the platform), the solution is to re-mill the motor foot plane.
(4) The deflection of the motor shaft changes
Generally occurs in the high voltage 2 pole motor, sliding bearing motor, in the user site (warehouse) placed for a long time, or after stopping, does not regularly rotate the motor shaft 180 °, resulting in a large deflection of the motor shaft (bending), after the power on the motor vibration value exceeds the standard.
To solve the problem of excessive vibration value of this kind of motor, it is generally necessary to do dynamic balance on the rotor again, which can reduce the vibration value of the motor.
(5) The natural frequency of the motor is close to that of the base
The overall natural frequency of the motor and the foundation is close to the 1 or 2 times frequency of the motor (the avoidance rate is not enough), and the vibration value will also exceed the standard after the motor is energized; It can be determined by vibration detection (spectrum analysis). In this case, it is necessary to strengthen the foundation to solve the problem of excessive vibration value.
(6) The vibration value of the motor in single test is qualified, but the vibration value with load exceeds the standard.
After the rotating parts of the main engine (rotor) and the rotor of the motor are connected, the alignment meets the standard requirements, but due to the large residual unbalance of the whole shafting system, the excitation force generated causes the vibration value of the motor to exceed the standard.
At this time, you can take off the coupling, rotate either one of the two couplings 180 degrees, and then connect the two couplings to test the machine, and the vibration value will drop.
(7) The problem of centering
There is no problem with the coupling between the motor and the main engine, but the deviation to the middle is large, resulting in excessive vibration value of the motor.
