When the motor is in working condition, the noise (single motor) can reach as low as 35dB, and the ambient noise is already higher than the noise of the motor itself. However, when multiple motors are running together under the same machine, they usually produce large noise, some even to the extent that the human body is not adaptable, so in this case, it is urgent to reduce the motor noise on the premise of not affecting the performance of the motor.
This article will focus on the many types of motor noise, how to effectively reduce noise, and what benefits OEMs can reap by reducing noise.
The types of motor noise can be classified according to the causes and characteristics of their occurrence. In general, motor noise mainly includes the following types:
| 1. Mechanical noise | 5. Harmonic noise |
| 2. Aerodynamic noise | 6. Noises caused by temperature |
| 3. Electromagnetic noise | 7. Nonlinear noise |
| 4. Gear noise |
1. Mechanical Noise
Mechanical noise is usually caused by the mechanical parts inside the motor, mainly from friction, vibration and imbalance. Common mechanical noises include:
Friction noise: The noise generated by friction of the internal components of the motor (such as bearings, gears, fans, etc.). This usually happens in the case of poor lubrication or wear of components.
Vibration and noise: Vibration when the motor is running can cause noise, especially when the rotor is unbalanced, the installation is not secure, or the bearing is damaged, the vibration can be exacerbated and cause noise.
Unbalanced noise: Unbalanced parts such as rotors and fans can also cause vibrations, which in turn can produce noise. This imbalance is usually due to manufacturing or installation errors.
Aerodynamic noise is caused by the movement of air generated when the motor is running. This is especially evident in air-cooled motors or fan motors. Air flow and contact between the air flow and components such as blades and housings can produce airflow noise, including:
Airflow noise: The interaction of the fan, blades, or air ducts of a motor with the air flow causes the air to vibrate, which in turn produces noise. Airflow noise is more noticeable at high speeds.
Blade windcut sound: When the blades of fans, motor radiators, etc. rotate, the air will cut the edge of the blades to produce noise, especially in the case of high-speed rotation.
Electromagnetic noise is noise caused by changes in the electromagnetic field of a motor. This type of noise usually originates from the interaction of electric currents and magnetic fields in the electric motor, and mainly includes:
Magnetic noise: In a motor, when an electric current passes through the stator windings and acts with a magnetic field on the rotor, the change in magnetic force causes mutual attraction and repulsion between the rotor and stator, which causes vibration and produces noise. Especially when the motor is operating, the change in load can cause magnetic fluctuations.
Current noise: In DC motors or brushless motors, rapid switching of currents (such as the operation of an inverter or drive) can also cause noise, especially in the case of frequent speed regulation.
Gear systems in electric motors, such as planetary gears or worm gears, are a common source of noise, especially during high-load operation or long periods of use. Gear noise typically includes:
Meshing noise: The gears will mesh with other gears during operation, and the resulting impact and friction will cause noise. The precision of the gear meshing and the state of lubrication have a significant impact on the noise.
Sliding noise: In some special gear transmission systems, such as worm gears, sliding friction between gears may produce additional noise.
Harmonic noise is often related to the electrical system of a motor, especially when the motor is running, changes in frequency and waveform can cause harmonics to be generated. These harmonic noises are usually generated when the variable frequency drive or the power is unstable. The main features are:
Frequency noise: Speed control devices such as frequency converters may produce noise of a specific frequency, which is usually periodic, single frequency or multiple frequency tones.
Electrical Interference Noise: Electrical noise may occur when the current and voltage waveforms are irregular, especially when the equipment has a sudden change in load or the power quality is unstable.
When a motor is operating in a high-temperature environment, the increase in temperature can cause the material inside the motor to expand or deform, which can cause friction or contact between mechanical parts, resulting in noise. Overheating of the motor may cause excessive thermal expansion, which in turn can cause unwanted noise.
When the motor is started or there is a sudden change in load, it may produce irregular noises that cannot be classified as the above types. They often appear as sudden noises that can be related to changes in torque or speed of the motor.
The noise of the motor mainly comes from many aspects such as machinery, aerodynamics, electromagnetism, gears, harmonics and so on. Each noise type has its root cause, and understanding these noise types can help you take countermeasures to reduce noise during motor design and use. For example, measures such as selecting the right motor type, improving component design, optimizing lubrication and reducing friction, and installing shock-absorbing materials can effectively reduce motor noise and improve product comfort and performance.
| 1. Choose a low-noise motor design | 6. Use high-quality gear system |
| 2. Fine mechanical design | 7. Use noise isolation and sound-absorbing materials |
| 3. Optimize the structure and installation of the motor | 8. Regular maintenance and inspection |
| 4. Adjust the motor control system | 9. Use a more suitable motor type |
| 5. Optimize the motor cooling system |
1. Choose a low-noise motor design
Brushless motor (BLDC): Compared with traditional brushed motors, brushless motors have no brushes and commutators, so there is no noise caused by brush wear, and they run more smoothly and with lower noise.
Permanent magnet synchronous motor (PMSM): This type of motor generates a constant magnetic field through permanent magnets, runs more smoothly, has high efficiency and low noise, and is suitable for environments that require quiet operation.
Dynamic and static balance optimization: Ensure that components such as motor rotors and fans are precisely adjusted for dynamic and static balance to avoid vibration and noise caused by imbalance.
Optimize rotor design: Reduce vibration during operation by reasonably designing the shape, material and manufacturing tolerance of the rotor. Accurate design can reduce airflow resistance and mechanical friction, thereby reducing noise.
Reduce bearing friction: Use high-precision ball bearings or ceramic bearings to reduce the noise caused by friction. Bearing lubrication needs to be checked regularly to ensure low noise during long-term operation of the motor.
Enhance the rigidity of the motor housing: By strengthening the structure of the motor housing, the vibration of the housing can be avoided to cause noise. Using thick-walled materials can reduce resonance and reduce noise.
Use shock-absorbing materials: Use rubber pads or other shock-absorbing materials on the motor mounting bracket to reduce the transmission of vibration generated when the motor is working to other components, thereby reducing noise.
Improve air duct design: In air-cooled motors, optimizing the air duct design can reduce the noise generated by air flow. Avoid sharp turns or irregular shapes in the air duct to reduce wind resistance and airflow noise.
Use inverter: Through variable frequency speed regulation (VFD), the running speed of the motor can be adjusted according to different loads. Avoid running the motor at high speed, which can not only reduce noise but also improve efficiency. Variable frequency speed regulation can also reduce the impact at startup and reduce the noise at startup.
Soft start and vibration reduction control: Use soft start devices to avoid severe vibration and noise when the motor starts. Noise can also be reduced through smooth acceleration and deceleration control.
Optimize drive waveforms: Use advanced drive design to optimize the waveforms of current and voltage to reduce electromagnetic noise and vibration noise.
Improve the design of cooling fans: The cooling fan of the motor may generate loud noise when running at high speed. Reduce the airflow noise generated by the fan by using a low-noise fan design or adjusting the fan speed and shape.
Improve cooling efficiency: Using a more efficient cooling system (such as a liquid cooling system) can reduce the operating load of the fan, thereby reducing the noise generated by air flow.
Gear meshing optimization: In motors with gear transmission, gear noise can be reduced by optimizing the gear meshing design. For example, using higher-precision gears and better lubrication can reduce the impact and friction of the gears during meshing and reduce noise.
Choose the appropriate gear type: For example, worm gear transmission systems are relatively quiet and suitable for applications with high noise requirements. If possible, choose a gear drive that is suitable for low noise.
Soundproof covers and sound-absorbing materials: Soundproof covers can be installed for motors, especially in noisy equipment. The cover uses sound-absorbing materials (such as foam, mineral wool, sound insulation cotton, etc.) to reduce the transmission of sound.
Internal and external sound-absorbing coatings: Applying sound-absorbing coatings inside and outside the motor housing can help absorb and reduce noise caused by mechanical vibration.
Regular maintenance of motors: Regularly check the bearings, gears, lubrication systems, etc. of the motor to ensure that each component is in the best condition to avoid increased noise due to wear, lack of oil, etc.
Clean the motor and fan: Regularly clean the dust and debris inside the motor to avoid dust accumulation that causes unbalanced rotating parts or increased friction, which in turn causes noise.
Choose the right motor type according to the application: Different applications have different requirements for noise, and choosing the right motor type is crucial. For example, for applications with high requirements for low noise, it would be more appropriate to choose a brushless DC motor or a permanent magnet synchronous motor because they produce less noise than traditional brushed motors.
Reducing motor noise without affecting performance and efficiency requires comprehensive consideration of motor design, manufacturing precision, control method and operating environment. By selecting low-noise motors, optimizing mechanical and control system design, using high-quality components and performing regular maintenance, motor noise can be effectively reduced, and product quality and user experience can be improved. With the help of these measures, unnecessary noise pollution can be reduced while ensuring efficient operation of the motor.
Original equipment manufacturers (OEMs) can gain several key business and technical advantages by reducing motor noise. These benefits not only improve product quality and customer satisfaction, but may also bring competitive advantages in the market. The following are the main benefits of reducing motor noise for OEMs:
| 1. Improve product competitiveness | 6. Enhance brand image and sense of social responsibility |
| 2. Improve customer satisfaction and brand loyalty | 7. Broaden the scope of market application |
| 3. Save operating costs | 8. Enhance customer health and comfort |
| 4. Improve the reliability and durability of products | 9. Improve equipment efficiency and safety |
| 5. Comply with regulatory requirements and industry standards |
Improve market appeal: Reducing noise can make products more attractive in the market, especially in industries where consumers have high requirements for noise control (such as home appliances, automobiles, office equipment, etc.). Products with low noise are often considered to be high-quality and high-tech representatives.
Differentiated competition: In a market with fierce competition for homogeneous products, low-noise products can become a major competitive advantage for OEM companies, helping their products stand out from other similar products.
Enhance user experience: Low-noise products can provide a quieter and more comfortable use experience, especially in home appliances, office equipment, medical equipment and transportation, where noise control is crucial for consumers. Customer satisfaction with product noise directly affects brand loyalty.
Reduce user complaints and return rates: Low noise can effectively reduce customer complaints and returns caused by noise problems, improve customer satisfaction and brand image.
Reduce energy consumption: Many noise reduction designs can also improve the efficiency of the motor. For example, by optimizing the rotor design of the motor or using a high-efficiency brushless motor, OEMs can not only reduce noise, but also improve energy efficiency and reduce energy loss, thereby saving operating costs.
Reduce maintenance costs: Low noise design usually means less vibration, friction and mechanical stress, which helps to extend the life of the motor and other components, reduce the frequency of equipment repair and replacement, and reduce long-term maintenance costs.
Reduce vibration loss: Noise is often closely related to vibration. By reducing the vibration of the motor, OEMs can improve the stability and durability of the product and reduce mechanical failures and component wear caused by excessive vibration.
Extend product life: Noise reduction is usually associated with higher design precision and better component matching, resulting in an extended life of the motor and related components.
Comply with environmental protection and noise control standards: In many countries and regions, especially in the European and American markets, noise pollution is regarded as an important environmental issue. By reducing motor noise, OEMs can ensure that their products meet local noise emission standards or environmental regulations and avoid potential legal risks and fines.
Raise market entry barriers: Some markets (such as high-end home appliances, office equipment or transportation) have strict requirements for noise control. Reducing motor noise can help meet these standards and expand market share.
Strengthen environmental image: Many consumers and companies are increasingly concerned about the environmental friendliness of products. Low-noise motors not only help reduce noise pollution, but also reduce energy consumption, which helps to enhance the environmental image of OEMs and gain recognition and support from consumers.
Enhance brand reputation: Producing low-noise products shows the professionalism and responsibility of OEM companies in R&D and manufacturing, which helps to shape a good brand image and increase public trust and awareness of the brand.
Applicable to more sensitive industries: Low-noise motors have greater application potential in some noise-sensitive industries (such as medical equipment, home appliances, office equipment, etc.). By reducing noise, OEMs can enter these markets and provide more competitive products.
Meet special needs: Some special industries or applications (such as high-end home furnishings, medical equipment, and quiet office environments) have very high requirements for noise. Reducing motor noise can help OEMs meet the needs of these market segments and expand market share.
Improve comfort: Low-noise equipment can greatly improve the comfort of the use environment. For example, in environments such as homes, offices, or hospitals, low-noise equipment helps create a quiet and comfortable space, which meets consumers' pursuit of health and comfortable life.
Reduce noise pollution: Noise pollution has become an environmental problem worldwide. Low-noise equipment can not only improve the user experience, but also reduce noise pollution to the surrounding environment, which meets the needs of modern society for sustainable development.
Improve operating efficiency: Low noise is often accompanied by higher operating efficiency and better heat dissipation design. By reducing motor noise, OEM products are generally able to provide more stable and efficient performance, especially when running for a long time.
Reduce safety hazards: The high noise of the motor may mask other potential mechanical failures or operating abnormalities. By reducing noise, OEMs can ensure that equipment is safer during operation and detect potential failure risks in a timely manner.
Summary:
Reducing motor noise can not only improve product market competitiveness, customer satisfaction and brand image, but also bring OEMs many benefits such as reducing operating costs, improving product durability and meeting regulatory requirements. These advantages make low noise technology a key factor that OEMs cannot ignore in the product design and manufacturing process, especially today when user experience and environmental sustainability are increasingly valued.
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