Reasons for abnormal noise of brushless motor.
In practical applications, brushless DC motors (BLDC) are widely used in industrial, automotive, consumer electronics, and other fields due to their smooth operation, low noise, and long lifespan. However, even if the design is excellent, there may still be "abnormal noise" issues during operation. This kind of abnormal noise not only affects the user experience, but may also indicate potential faults inside the motor. In order to help users quickly locate and troubleshoot problems, the following is a comprehensive analysis of common causes and solution suggestions for brushless motor abnormal noise.
1、 Electromagnetic noise
1. Improper reversing control
Brushless motors use electronic commutation. If there is an error in the Hall sensor or controller commutation logic, it may result in inaccurate commutation timing, periodic electromagnetic vibration, and "buzzing" or "giggling" sounds.
Solution:
Check if the Hall sensor is installed properly;
Optimize the controller commutation logic;
The use of FOC vector control can effectively reduce electromagnetic noise.
2. Current imbalance in stator winding
If the current of the three-phase winding of the brushless motor is uneven (such as abnormal PWM output of the controller), it will cause magnetic imbalance and irregular electromagnetic noise.
Solution:
Check if there are any driving abnormalities in the controller;
Check if the resistance of the three-phase winding is consistent;
Use an oscilloscope to analyze the PWM output waveform.
2、 Mechanical structural issues
1. Unbalanced or eccentric rotor
Improper installation or long-term operation of the rotor can cause eccentricity and imbalance of dynamic balance, leading to significant mechanical vibration, manifested as periodic "buzzing" or "clicking" sounds.
Solution:
Re calibrate the rotor balance;
Check the concentricity between the bearing seat and the motor housing;
Use a dynamic balance meter for testing and calibration.
2. Bearing wear or poor lubrication
Drying up of lubricating grease inside bearings, damage to steel balls or raceways can cause sharp and piercing metal friction sounds during motor rotation.
Solution:
Replace high-quality bearings;
Use lubricating grease suitable for the speed level;
Pay attention to the clearance and direction of bearing installation.
3. The installation is not securely fastened
Loose connections between the brushless motor and the frame, or loose flange screws, can cause resonance and mechanical noise during operation.
Solution:
Check all fixed components, especially the motor base and installation screws;
Install shock-absorbing pads or soft connection structures;
Re tighten and apply anti loosening adhesive.
3、 Interference noise caused by control system
1. Improper PWM frequency setting
The PWM frequency of the driver is too low, which can easily cause sharp switching sounds (4kHz~20kHz) that can be perceived by the human ear, and is a common source of electromagnetic interference.
Solution:
Adjust the PWM frequency beyond the audible range of the human ear (≥ 20kHz);
Use high-quality driver chips and filtering capacitors.
2. Controller interference
Poor grounding or improper wiring of the controller may also cause induced noise to be superimposed on the sound of motor operation.
Solution:
Optimize the grounding and wiring of the controller;
Add EMI filters or ferrite magnetic rings;
Ensure isolation between signal lines and power lines.
4、 Environmental and load factors
1. Uneven load or external impact
If the load driven by the motor experiences eccentricity, imbalance, or jamming, it can also transmit vibration or impact to the motor, causing abnormal noise.
Solution:
Check whether the mechanical structure is symmetrical and balanced;
Is the load axis concentric;
Exclude lagging or mechanical wear phenomena.
2. Dust or impurities entering the working environment of the motor
Although brushless motors have good sealing properties, foreign objects may enter the interior of the motor when operating in high dust or oil mist environments, causing slight friction or whistling sounds.
Solution:
Regularly clean the surface of the motor;
Install dust cover or sealing sleeve;
Choose motor models with high protection levels (such as IP65 or above).
5、 Common types of abnormal noises and comparison table for troubleshooting
Possible causes of abnormal noise types and key inspection points
Uneven buzzing electromagnetic force, commutation error, PWM noise controller parameters, Hall signal, winding current
Metal friction sound bearing damage, rotor stator friction bearing, axial clearance, stator position
Click sound, loose screws, rotor impact, load impact, installation bolts, dynamic balancing, load structure
Sharp whistling sound, low PWM frequency, electromagnetic interference, grounding issues, driving frequency, wiring, power filtering
Intermittent abnormal noise Hall signal loss, load lag, encoder fault control signal, motor load, encoder
Conclusion: Correct judgment and handling to ensure stable operation of brushless motors
Although the abnormal noise of brushless motors may not immediately affect system operation, it is often a precursor to potential faults. Through systematic investigation and targeted treatment, not only can abnormal noise be effectively eliminated, but the service life of the motor can also be extended and the overall operating quality can be improved. It is recommended that if any abnormal noise is found during the operation of the motor, it should be stopped immediately for inspection, and a comprehensive analysis and optimization should be carried out from four aspects: electromagnetic system, mechanical structure, controller, and load.
