Electromagnetic vibration caused by uneven air gap
When the center of the stator of the motor does not coincide with the axis of the rotor, the air gap between the stator and the rotor will appear eccentric. This air gap eccentricity is often fixed at a certain position, and it does not change its position with the rotation of the rotor.
1. Eccentric electromagnetic vibration characteristics of static air gap
The vibration increases with the increase of the eccentric value, and the relationship with the motor load is also the same;
The electromagnetic vibration caused by the eccentricity of the air gap is difficult to distinguish from the electromagnetic vibration caused by the abnormality of the stator.
2. Air gap dynamic eccentric electromagnetic vibration
The dynamic eccentricity of the motor air gap is caused by the deflection of the rotating shaft, the non-circular rotor core or the non-concentricity between the rotor and the shaft. The eccentric position is not fixed to the stator but fixed to the rotor. Therefore, the eccentric position follows the rotation of the rotor And synchronous movement.
Dynamic Eccentricity Electromagnetic Vibration Characteristics of Air Gap
Electromagnetic vibrations may occur at both the rotor rotational frequency and the synchronous rotational speed frequency of the rotating magnetic field.
The electromagnetic vibration is pulsating with a period of 1/(2sf0), so when the motor load increases and s increases, the pulsation beat is accelerated.
Electric motors tend to generate electromagnetic noise consistent with the pulsating beat.