How to effectively reduce motor noise
The noise of the motor includes electromagnetic noise, mechanical noise and ventilation noise. The noise of a motor is basically a combination of many kinds of noise. In order to meet the requirements of low noise of the motor, we should comprehensively analyze the factors affecting the noise and take measures.
Part processing accuracy control is a relatively 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, the mechanical noise of the motor can be effectively reduced by adopting low-noise bearings; The electromagnetic noise of the motor can be effectively reduced through the coordination adjustment of the slots of the stator and the rotor and the adjustment of the slope of the rotor slots; The other is to adjust the air path of the motor. Take measures on the fan and hood of the motor to reasonably grasp the relationship between motor noise, temperature rise and efficiency.
Electromagnetic noise is mainly caused by magnetostriction and vibration of the iron core caused by periodic radial electromagnetic force or unbalanced magnetic tension in the motor. Electromagnetic noise is also related to the vibration characteristics of stator and rotor itself. For example, when the exciting force resonates with the natural frequency, even a small electromagnetic force will produce a lot of noise.
The suppression of electromagnetic noise can be started from many aspects. For asynchronous motors, first of all, choose the appropriate number of stator and rotor slots. Generally speaking, there is a large difference between the number of rotor slots and the number of stator slots, that is, when the so-called far slot is matched, the electromagnetic noise is small. For slotted motors, the chute can make the radial force phase shift along the motor axis, so the axial average radial force is reduced, thus reducing the noise. If the double chute structure is adopted, the noise reduction effect is better. The double chute structure divides the rotor into two sections along the axial direction. The torsion direction of each slot is opposite. An intermediate ring is also arranged between the two sections.
In order to reduce the harmonic of magnetic flux, double-layer short moment winding can be used. Fractional slot winding shall be avoided. Sinusoidal windings shall be used in single-phase motors. In order to reduce the electromagnetic noise caused by the tooth groove, the magnetic slot wedge can be used or the slot width of the stator and rotor can be reduced until the closed slot is used. When the three-phase motor is running, the voltage should be symmetrical as much as possible, and the single-phase motor should run in a rotating magnetic field close to the circle. In addition, during the manufacturing process of the motor, 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 rotor should be ensured to make the air gap uniform. Reducing the air gap flux density and adopting a larger air gap can reduce the noise. In order to avoid the resonance between the electromagnetic force and the natural frequency of the housing, an appropriate elastic structure can be used.