Views: 0 Author: Site Editor Publish Time: 2025-09-28 Origin: Site
Motor noise is a significant factor affecting motor performance and operating environment. It primarily consists of airborne noise, mechanical noise, and electromagnetic noise. Each noise type has its own unique source and control methods.
The following is a detailed analysis of these noise types, along with formulas, tables, and examples, to provide a more comprehensive understanding of noise sources and control measures.
Air noise is usually generated by the rotation of the fan inside the motor. The size, shape, speed and air duct design of the fan will affect the intensity of the noise. The process of air flow, collision and friction will generate noise. Especially when the fan blade shape is unreasonable or the air duct design is inappropriate, it will generate more significant noise.
1. Design the fan and blade shape appropriately to avoid eddy currents;
2. Ensure a reasonable gap between the blade edge and the ventilation chamber;
3. Reduce the fan diameter to reduce noise, and optimize the air path design to minimize air impact and friction;
4. Use a soundproofing cover and soundproofing materials to reduce the impact of external noise.
Assume that the fan noise level (Lw) can be calculated by the following formula:
Where P is the noise power generated by the fan and P0 is the reference noise power (10-12 W).
Mechanical noise mainly comes from bearings, rotor imbalance, and friction between carbon brushes and commutators. The quality of the bearings, the choice of grease, the dynamic balancing accuracy of the rotor, and the friction quality of the carbon brushes and commutator all have an impact on the noise.
Bearing noise is closely related to bearing accuracy, grease selection and installation error. Common bearing noise levels can be expressed by the following formula:
Where Lb is the bearing noise level, Lb0 is the reference noise level, N is the bearing speed, and N0 is the reference speed.
Rotor imbalance can cause motor vibration and increase noise. The vibration frequency of the rotor is related to the speed (N) and can be calculated by the following formula:
Where fv is the vibration frequency, N is the speed in rpm, and P is the number of pole pairs.
The friction noise between the carbon brush and the commutator can be reduced by optimizing the design. The intensity of the friction noise is related to the flatness of the commutator surface and the pressure of the carbon brush.
1. Use high-quality bearings to ensure bearing accuracy;
2. Reduce bearing installation errors to ensure rotor balance;
3.Design and optimize the friction characteristics of the carbon brushes and commutator.
Electromagnetic noise is generated by the alternating electromagnetic forces between the stator and rotor of a motor. These forces act on the stator and rotor, causing them to vibrate and generate noise. The frequency of electromagnetic noise mostly ranges from 100Hz to 4000Hz, and its frequency is closely related to factors such as motor design and the characteristics of the air gap magnetic field.
1.Design an appropriate stator and rotor slot alignment to avoid low-frequency force waves;
2. Increase the stator and rotor air gap to reduce magnetic flux density;
3. Optimize rotor slot design and utilize remote slots and multiple slots to reduce electromagnetic noise.
1.The combination of the number of rotor slots, stator slots, and pole pairs determines the frequency of electromagnetic noise.
2. High-order harmonic components in the current can also cause electromagnetic noise.
Noise Type Control Measures | Noise Type Control Measures |
Airborne Noise | Optimize fan and air duct design and use sound-absorbing materials to reduce the impact of external noise. |
Mechanical Noise | Optimize bearing design, increase dynamic balance accuracy and reduce friction noise. |
Electromagnetic Voise | Design a reasonable stator and rotor slot fit, increase the air gap, and optimize the rotor slot design. |
By comprehensively considering the control measures for these noise types, the operating comfort of the motor can be effectively improved and its service life can be extended.
