1. Motor vibration source and identification
(1) Whether the rotor working speed is close to the critical speed. By calculating the torsional rigidity of the motor shaft and whether the torsional vibration frequency of the motor is close to the critical speed of the motor, the angular frequency of the pump and the frequency of the power grid, the resonance can be generated. In particular, when the motor is used for the first time, the vibration failure should be analyzed and calculated. The working speed of the motor rotor should be at least 25% lower than the critical speed or about 40% higher than the critical speed. In the analysis, it is also necessary to take into account that the mass of the motor rotor can not be simplified into a concentrated mass, but is distributed along the axis, so the critical speed should be analyzed to the second and third order critical speed.
(2) Unbalance of motor rotor.
The unbalance of the motor rotor is the main and common cause of vibration, such as: 17#, 19# motor, with the speed vibrometer (displacement meter) measured the motor vibration speed of 9.8-l0mm/s, according to the IS02372 vibration speed standard, Class III machinery should be less than 4.5mm/s, and in the 9.8-l0mm/s state, the motor amplitude measured by the vibrometer reached 0.30mm. In order to find out the unbalance degree of the motor rotor, we made two pairs of steel frames on the site to erect two parallel rails (pay attention to the steel frame should have sufficient stiffness), the upper surface of the rail was treated into a smooth clean surface, and the rail surface was adjusted and fixed with a level. During the inspection, the motor rotor is placed on the two rails, and the rotor is rolled back and forth several times by hand. After each time it is stationary, mark the bottom of the rotor. Paste the adhesive on the symmetric point of the biased position, and then rotate the rotor several times until the rotor can be stopped at any position to confirm that the motor rotor has reached a static balance state. Replace the paste with equivalent mass to complete the balance of the motor rotor. If the above method can not solve the problem, it is necessary to make the motor rotor dynamic balance test. After the balance weight of 45-5g is added to the rotor side of the two motors, the amplitude value is reduced to 0.05mm, and the vibration speed value measured by the displacement meter is about 2.1mm /s.
(3) For the motor that has been normally used for a period of time, the cause of vibration should be checked whether the bearing clearance is too large, whether the shaft seat fixing screw is loose, whether the shaft is worn and bent, or a certain part of the winding short circuit, the air gap is uneven, and the annular gap between the rotor and the stator should not exceed 10%.
It is particularly noteworthy that when the amplitude value of the motor is close to the standard value, that is, it is still considered to be within the qualified range, the amplitude value of the motor will often exceed the standard after loading, because the vibration factors of the entire deep well pump transmission system are the result of mutual influence and joint action.
