The noise of the motor includes electromagnetic noise, mechanical noise and ventilation noise. The noise of a motor is basically a combination of various noises. To achieve the low noise requirements of the motor, the factors affecting the noise should be comprehensively analyzed and measures should be taken.
Parts machining accuracy control is a more effective measure, but it must be guaranteed by good equipment and technology. Such measures can ensure the overall matching effect of motor parts; in addition, low-noise bearings can be used to effectively reduce the motor’s Mechanical noise; the electromagnetic noise of the motor can be effectively reduced through the adjustment of the slots of the stator and the rotor, and the adjustment of the inclination of the rotor slots; the other is the adjustment of the motor air path. Take measures on the cover to reasonably consider the relationship between motor noise, temperature rise and efficiency. Objectively speaking, the development needs of motor products constantly put forward new topics to the manufacturers of motors.
Electromagnetic noise of the motor
Electromagnetic noise is mainly caused by the magnetostriction and vibration of the iron core caused by the periodic changing radial electromagnetic force or the unbalanced magnetic pulling force in the motor. Electromagnetic noise is also related to the vibration characteristics of the stator and rotor itself. For example, when the excitation force and the natural frequency resonate, even a small electromagnetic force can generate a large amount of noise.
The suppression of electromagnetic noise can be started from many aspects. For asynchronous motors, the first thing to do is to select the appropriate number of stator and rotor slots. Generally speaking, the difference between the number of rotor slots and the number of stator slots is relatively large, that is, when the so-called remote slots are matched, the electromagnetic noise is small. For the slotted motor, the inclined slot can make the radial force produce phase displacement along the motor axis direction, thus reducing the average axial radial force and thus reducing the noise. If the double inclined groove structure is adopted, the noise reduction effect is better. The double inclined groove structure divides the rotor into two sections along the axial direction. The skew direction of each slot is opposite. There is also an intermediate ring between the two segments.
In order to reduce the magnetomotive force harmonics, double-layer short-moment windings can be used. And avoid fractional slot windings. In single-phase motors, sinusoidal windings should be used. In order to reduce the electromagnetic noise caused by cogging, magnetic slot wedges can be used or the slot width of the stator and rotor can be reduced until closed slots are used. When three-phase motors are running, voltage symmetry should be maintained as much as possible, and single-phase motors should operate in a nearly circular rotating magnetic field. In addition, in the motor manufacturing process, the ovality of the inner circle of the stator and the outer circle of the rotor should be reduced and the concentricity of the stator and the rotor should be ensured to make the air gap uniform. Decreasing the air gap flux density and using a larger air gap can reduce noise. In order to avoid the resonance between the electromagnetic force and the natural frequency of the casing, an appropriate elastic structure can be used.
Post time:
Jul-27-2022