Mechanical reasons:
1. The journal is elliptical or curved. When the motor rotates, the gravitational force of the rotor will produce interference vibration, and its vibration frequency is usually twice the working frequency of the motor. The bending of the shaft causes the unbalanced weight to rotate around the static equilibrium position at an angular velocity, and the result is the same as the unbalance of the rotor. When turning, a dial gauge can be used to measure the ovality of the journal or the curvature of the shaft. The journal ellipse must be rounded after welding or brush plating, and the shaft must be corrected when the shaft is bent;
2. The armature is unbalanced. As the unbalanced mass produces centrifugal force when rotating, the rotating force acts on the bearing, causing vibration of the motor and foundation. When the air gap is uneven, the main rod is not tightly fixed, or the base and end cover are poor in rigidity, the vibration will increase. Therefore, when checking the unbalance of the rotor, the dynamic balance must be rebalanced;
3. The manufacturing error or operation deformation of important supporting parts of the base and end cover. Because the shape and position error of important rotor support parts such as frame and end cover is out of tolerance, especially when large and medium-sized motors are running for a long time, the frame, end cover and other important support parts are deformed, causing the bearing to interfere with the force during the operation of the motor. , Causing the motor to vibrate;
4. The radial clearance of the bearing is too large, and the outer ring and the end cover are loose. When assembling, the bearing should be inspected to pass. The matching of bearings, journals and bearing seats must meet the requirements, otherwise, spraying or brushing processes must be used for treatment to avoid vibration caused by poor bearing work. For worn bearings, the vibration and noise frequencies of the motor during operation are relatively high, and it is easier to judge. If this situation is found, the bearing should be replaced;
Electrical reasons:
1. Uneven air gap. Due to the uneven disassembly air gap, unilateral magnetic tension will be generated when the motor is running, and its effect is equivalent to an increase in the deflection of the motor shaft. Therefore, ensuring the average disassembly of the air gap is a necessary measure to avoid vibration;
2. The rotor coil is damaged. Due to the damage of the rotor coil, the radial force of the rotor is not uniform when the motor is running, and the consequence is similar to the imbalance of the rotor;
3. Electromagnetic force. This electromagnetic force is mainly caused by the longitudinal oscillation of the magnetic flux under the pole shoes, usually with tooth frequency, especially when the stator is also open to the cogging, the magnetic flux pulsation increases, and it is easier to form an alternating magnetic pulling force.
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