【 Coreless motor 】The cause of the specific vibration of the DC geared motor

DC geared motor often vibrates, what is the reason for it?

  1. Mechanical reasons

1. The journal is elliptical or the rotating shaft is bent. When the motor rotates, interference vibrations occur due to the gravity of the rotor, and the vibration frequency is usually double the operating frequency of the motor. The bending of the shaft creates an unbalanced weight that rotates around the statically balanced position at angular velocity, with the same result as rotor unbalance. The journal ellipse or shaft bending can be measured by dial gauge when cruising, the journal ellipse must be rounded after welding or brush plating, and the shaft must be corrected when bending;

2. The armature is unbalanced. Due to the effect of the centrifugal force generated by the unbalanced mass during rotation, there is a rotational force acting on the bearing, which causes the vibration of the motor and the foundation. When the air gap is uneven, the main pole is not tightly fixed or the stiffness of the base and end cover is poor, the vibration will be aggravated, so when the rotor is found to be unbalanced, the dynamic balance must be re-balanced;

3. Manufacturing errors or deformation of important supporting parts of the base and end cover. Due to the deviation of the shape and position error of the mating surface of the important supporting parts of the rotor such as the base and end cover, especially the deformation of the important supporting parts such as the base and end cover after the operation of large and medium-sized motors for a long time, the bearing of the motor produces interference force during operation, 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. At the time of assembly, the bearing should be inspected and qualified. The fit between the bearing and the journal and the bearing seat must meet the requirements, otherwise it must be treated by spraying or brushing to avoid vibration caused by poor bearing work. For wear bearings, the frequency of vibration and noise is higher when the motor is running, and it is easier to judge, and the bearing should be replaced when this situation is found;

  Second, the electrical reason

1. The air gap is uneven. Due to the uneven disassembly air gap, unilateral magnetic pull occurs when the motor is running, which is equivalent to the deflection of the motor shaft. Therefore, ensuring that the air gap is disassembled evenly is a necessary measure to avoid vibration.

2. The rotor coil is damaged. Due to the damage of the rotor coil, the rotor is subjected to uneven radial force when the motor is running, and the consequences are similar to rotor imbalance.

3. Electromagnetic force. This electromagnetic force is mainly caused by the longitudinal oscillation of the magnetic flux under the pole shoe, and usually has a tooth frequency, especially when the stator is also a tooth groove, the magnetic flux pulse is added, and it is easier to form an alternating magnetic tension.