Characteristics and Main Causes of Rotor Shaft Unbalance
Characteristics of rotor shaft imbalance
(1) Common characteristics of vibration frequency band: Unbalance problem is generally dominated by high frequency shift vibration, and generally its frequency shift vibration is greater than or equal to 80% of its pass frequency vibration.
(2) The unbalanced force has a certain specificity, the centripetal force is basically symmetrical in the axial direction, and the trajectory of the shaft and the supporting bearing is similar to a circle. However, because the vertical support bending stiffness of the bearing with seat exceeds the vertical direction, the normal trajectory of the shaft and the support bearing is elliptical, that is, the horizontal vibration is 1.5 to 2 times larger than the vertical vibration under normal circumstances. Beyond this standard, any problems may arise, especially the coseismic problem.
(3) Compared with radial vibration, when the imbalance problem is dominant, the axial vibration (lateral and longitudinal) is much higher than the radial vibration (outside the suspended wall rotor).
(4) The unbalance problem of the suspended rotor shaft is specific. Generally speaking, the axial and radial vibrations are very large. At the same time, there is static unbalance and unbalance of the coupling couples. Thus, balance correction often requires 2 floor plans.
(5) Unbalanced vibration rotor vibration phase difference is smooth and repeated many times.
(6) The imbalance will also increase the coseismic amplitude. If the rotor operating speed is close to the resonance point of the system software resonance frequency, a small amount of unbalanced vibration will increase by 10 to 50 times.
(7) The phase difference of the rotor imbalance is mainly manifested. The vertical and capacity phase angle of the same rolling bearing is about 90 °, and the phase angle of the bearings on both sides in the same direction is the same.
There are many main reasons for rotor imbalance, which can be divided into initial imbalance, gradual imbalance, sudden imbalance, arbitrary imbalance and so on.
a) Static data imbalance:-The quality axis of the rotor shaft does not overlap with the rotating axis, and there is a certain axial force. However, the quality axis in the rotor length L is parallel to the rotation axis, so it will cause imbalance in a separate plane. The rolling bearings at both ends in the centripetal effect area have the same size and orientation, and need to be balanced and corrected by a separate plan view.
B) Symmetrical imbalance:-The quality axis of the rotor shaft does not overlap with the rotating axis, but crosses the center of gravity of the rotor. The centripetal force generated is the same and acts on the rolling bearings on both sides 180 degrees in reverse.
c) Specific unbalance:-The mass axis and the rotation axis of the rotor do not intersect, are not parallel or overlap, and the centripetal force generated by the unbalance acts on two planes. It can be felt that dynamic imbalance is a combination of static data imbalance or even imbalance, which is often the case in production operations.
Insert the insulating layer slot paper: the size and length of the insulating layer material must be consistent, the insertion posture must be consistent, and it must be ensured that the insertion is not easy to move.
Rotor shaft winding: the symmetrical winding method of double flying forks is selected, and it is stipulated that the supporting force of upper and lower flying forks is basically the same, and the stacking of wrapped wires is symmetrical and consistent.
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Rotor shaft
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2024-01-02
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