Efficient Measures to Reduce Motor Noise

Nowadays, noise control of motor has become an important chip to expand the market, especially the motor running in the residential environment, which has more stringent requirements.

The noise of motor includes electromagnetic noise, mechanical noise and ventilation noise.
Part processing accuracy control is an 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, motor mechanical noise can be effectively reduced by adopting low-noise bearings; Motor electromagnetic noise can be effectively reduced by adjusting the slot matching between the stator and the rotor and adjusting the slot inclination of the rotor; The other is the adjustment measures of motor air circuit. Many motor manufacturers take measures on motor fan and hood to reasonably grasp the relationship between motor noise, temperature rise and efficiency.

Electromagnetic noise is mainly caused by magnetostriction and vibration of iron core caused by periodic radial electromagnetic force or unbalanced magnetic tension in motor. Electromagnetic noise is also related to vibration characteristics of the stator and rotor. The suppression of electromagnetic noise can be started from many aspects. For asynchronous motor, the appropriate number of stator and rotor slots should be selected first. 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, electromagnetic noise is small. For slotted motor, the inclined slot can make the radial force phase shift along the motor axis, so the axial average radial force is reduced, then noise is reduced. 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.

To reduce the harmonic of magnetic flux potential, double-layer short moment winding can be used. Fractional slot winding shall be avoided. Sinusoidal windings shall be used in single-phase motors. 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 3-phase motor operates, the voltage symmetry shall be maintained as much as possible, and the single-phase motor shall operate in a rotating magnetic field close to a 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 shall be reduced, and the concentricity of the stator and rotor shall be ensured to make the air gap uniform. Reducing the air gap flux density and using a larger air gap can reduce the noise. In order to avoid the resonance between the electromagnetic force and the natural frequency of the casing, an appropriate elastic structure can be adopted.