Three-phase asynchronous motor rotor imbalance is due to the mass eccentricity of the rotor component or the rotor component defects, it is a common failure of rotating machinery. According to statistics, about 70% of failures in rotating machinery are related to rotor imbalance. Today, Dalan Motor Xiaobian led everyone to see what caused the rotor imbalance.
First, the design problem:
(1) The design of the geometry of the rotating body is asymmetric, and the center of gravity is not on the axis of rotation.
(2) There is an unprocessed surface inside or outside the motor rotor, causing uneven mass distribution.
(3) The mating surface of the part on the shaft is rough or the fit tolerance is not suitable, resulting in radial or axial oscillation. When it is too loose, the rotor bore expands to cause eccentricity at high speeds.
(4) The key on the shaft is fitted in the keyway to form a partial metal gap.
(5) The rotating parts on the shaft are not symmetrically installed, and there is a fitting clearance.
Second, material defects:
(1) Castings have pores, which result in non-uniform internal structure of the material. The thickness of the material is inconsistent. For example, the welded structure has asymmetrical quality because of different thicknesses.
(2) Material is poor, easy to wear, deformation caused by uneven quality distribution.
Third, processing and assembly errors:
(1) Molding defects on welding and casting.
(2) Cutting error in cutting.
(3) Accumulation of the fitting error during assembly of the impeller causes displacement of the center of gravity. Therefore, it is necessary to perform a dynamic balance for each impeller attached to the high-speed rotor.
(4) The heat treatment of the material does not meet the requirements of the conditions, or the residual stress is not eliminated and the distortion during welding is used to permanently deform the rotor.
(5) Asymmetrical quality due to inconsistent parts. Such as: screw depth or screw length is inconsistent.
(6) Coupling misalignment. For one of the rotors, a parallel misalignment is equivalent to adding an unbalanced load to the rotor. Therefore, it also shows an imbalanced characteristic.
Fourth, the dynamic balance method is wrong: For the flexible rotor, the vibration mode at its operating speed is significantly different from its first-order vibration mode. Therefore, the rotor is only dynamically balanced at low speeds, and large vibrations still occur at high speeds.
----- Editor: Dalan Oil Pump Motor 02 - Procurement Consultant
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