The noise generated by electrical equipment varies with the size and model of the equipment, and its noise pollution level is also different. The motor noise is mainly divided into two categories, one is the noise generated by electromagnetic equipment, and the other is the noise generated by motor mechanical equipment.

Among them, there are many reasons for the noise of mechanical equipment, most of which are caused by the wear and tear of electrical equipment in normal production, and many abnormal noises are caused by the misoperation of operators or the hidden danger of failure of electrical equipment. Therefore, as a motor technician, we should conduct investigations from various aspects to check out the cause of the motor noise, and effectively eliminate the noise with effective technological measures so that the motor noise exists in its normal form.

1 Main causes of motor noise in daily production

1.1 Noise generated by unbalanced components inside the motor equipment

The noise generated by motor equipment used in daily production is usually caused by the imbalance of mechanical equipment. There are three main types of unbalanced motor equipment: dynamic unbalanced, static unbalanced, and mixed unbalanced. As for the dynamic imbalance, it will cause centrifugal force, which will cause noise to vibrate each other on the support. The greater the noise in production, the more violent the vibration will be. In addition, the construction and later maintenance of electrical equipment are not paid attention to beforehand, and the noise of many electrical equipment will become louder. The static imbalance is mainly due to the size of the centrifugal force. Caused by phase vibration imbalance. Mixed unbalance is generally used in large-scale motor enterprises, and decision makers generally only pay attention to the role of dynamic balance in the production process;

1. 2 Noise generated by motor bearing wear

As one of the main components of motor equipment, the noise generated by bearings can be summarized as body noise and noise generated by motor matching components. Most of the noise generated by the motor body appears on the rolling bearings and rolling balls. There are shaft rings inside and outside these rolling bearings, and there are ball necklaces in them to ensure that the motor equipment can roll smoothly during the working process without causing huge noise due to friction or installation. In addition, in modern bearing production All will be equipped with noise measuring instruments and effective noise reduction instruments, which also occupy a majority position in the production of motor factories;

Since the noise generated by motor components is generally considered to be the bearing of the corresponding size, it is diverted to most motor manufacturers. After the decibel test of the noise, the noise emitted by the bearing is the largest. There are two reasons for this:

(1) The gap between the bearings is small, which cannot be matched with the original way of manufacturing the bearings, resulting in a gap between the inner ring and the outer ring after the bearings are installed in the motor. Long-term use will deform the bearings, causing friction and noise .

(2) The rigidity of the motor end cover and the base is not suitable to generate noise. Due to the elliptical deformation of the inner ring of the bearing assembled on the rotating shaft, the "tuning" of the vibration system between the bearing and the motor is weakened in the radial direction, thereby causing axial vibration with a large amplitude. It is worth noting that the electromagnetic force wave that causes the electromagnetic vibration of the stator core also acts on the rotor at the same time. In general, if the rotor stiffness is good, the bending vibration caused by it can be ignored, but it will be transmitted to the end cover and the whole motor through the bearing.

1.3 Motor noise caused by various reasons

There is another part of noise generation. Such as: In general, mechanical noise is the main source of motor noise. Usually, due to the need for heat dissipation, the sealing of the motor is limited, so that after long-term operation, the amount of dust absorbed will continue to increase, which affects the heat dissipation of the motor. The thermal stress generated during operation is likely to cause shaft bending and displacement, while the shaft Thermal bending and thermal displacement will in turn increase the noise of the motor.

2 Process measures to reduce motor noise

2.1 Solve the mechanical imbalance of the rotor to effectively control the noise

The unbalance of the rotor should be minimized as much as possible, otherwise the balance accuracy will be low.

The balance accuracy is related to the specifications, properties and operating conditions of the motor. For example: marine motors have large turbulence, long running time, low vibration and noise, and high balance precision requirements. The larger the diameter-to-length ratio of the rotor core, the greater the centrifugal force and the higher the balance accuracy.

The higher the rotational speed of the rotor, the higher the balance accuracy requirement. The basic conditions of the motor during use, such as the poor rigidity of the bearings and various supporting parts, require high balance accuracy.

2.2 Main methods of motor bearing noise reduction

The method of reducing bearing noise of motor equipment can start from the following points:

(1) Pay attention to the selection of bearings.

During the operation of most motor bearings, the vibration degree of the bearing will increase with the increase of the inner diameter of the bearing. For every 5mm diameter increase, the vibration will increase by about 1~2dB.

(2) Pay attention to the size of the radial clearance of the bearing.

Excessive radial clearance will cause low frequency noise to increase, conversely, too small clearance will cause high frequency noise to increase. In order to reduce the vibration and noise when the bearing rotates, it is advisable to control the radial working clearance of the bearing within the range of 1-9μm. the

(3) Appropriately pressurize the bearing.

Its purpose is to eliminate the axial clearance of the rotor. Generally, a wave spring washer or a three-point elastic washer can be selected, and placed at the end of the shaft extension.

(4) For motors with relatively high noise requirements, low-noise bearings should be selected.

When the load is small, the oil-impregnated sliding bearing can be used, and its noise is generally about 10dB lower than that of the rolling bearing of the same size.

(5) The same motor should be assembled with the same batch of bearings of the same specification and model produced by the same manufacturer to avoid mixed assembly.

2.3 Other noise reduction methods

There are many methods for the noise reduction process of electrical equipment, among which two examples are used to illustrate:

(1) The shaft configuration of the bearing should avoid the noise generated by the bearing due to repeated knocking. Before assembling the bearing, the bearing should be cleaned and degaussed. The thermal expansion method should be used during assembly, and the corresponding type of lubricating grease should be applied in an appropriate amount.

(2) The stator, rotor and bearings are responsible for the method of avoiding noise

Set up quality control points, implement key controls, and make the machining accuracy as close as possible to the middle value of the tolerance zone; at the same time, the technological level of the production enterprise, production equipment and tooling must be able to ensure the accuracy of machining. To improve the quality of mechanical processing, there must be absolute guarantees in the establishment of quality control points and testing methods.

3 Conclusion

To sum up, motor noise has a huge impact on people's lives, and it is a problem that must be solved in motor production.

In the production of motors, if the operation of the motor equipment is well controlled, noise pollution can be effectively reduced by cleverly using various processes to test the noise of the motor equipment. For various factors, the motor equipment should be continuously updated and new technology should be adopted. Means and methods ensure that motor noise is minimized. With the rapid development of science and technology in the future, it is almost impossible to completely eliminate noise. However, through the continuous innovation and hard-working spirit of our Jinzhi Datong technicians, the noise will be reduced to the level that people are satisfied with.