Brushless DC motors (BLDC) are widely used in many fields such as new energy vehicles, industrial robots, home appliances, and drones due to their advantages of high efficiency, low noise, and long lifespan. However, during long-term operation, various faults can still occur due to factors such as circuit matching, mechanical wear, and environmental influences. Statistics show that approximately 30% of industrial equipment downtime is related to BLDC motor malfunctions. Understanding common problems and mastering corresponding solutions is crucial for ensuring stable equipment operation. Below is a detailed overview of typical BLDC motor faults and their solutions.
I. Starting Abnormalities: Irregular Rotation or Failure to Start
Starting failure is one of the most common problems in BLDC motors, typically showing as short rotation, jitter, or complete inability to start. The main cause is a commutation logic error. Since brushless DC motors require six commutation steps for continuous operation, if the controller cannot correctly read the rotor position, timing errors can cause the motor to jam. Faulty Hall sensors—such as damaged units, incorrect pin configuration, or initialization errors - can also make the controller lose position feedback. Another common factor is an unstable power supply. BLDC motors draw a high inrush current at startup; if the supply voltage is low, internal resistance is high, or capacitors have insufficient capacity, the motor may fail to generate enough torque. In addition, improper PWM settings, such as incorrect frequency or low duty cycle, can prevent MOSFETs from switching properly.
To troubleshoot, check Hall sensor signals and PWM waveforms with an oscilloscope, verify commutation parameters, test supply voltage with a multimeter, and replace capacitors or power sources as needed to ensure stable startup performance.
II. Overheating: Shortened Lifespan or Even Motor Burnout
Overheating is a critical issue threatening the lifespan of BLDC electric motors. Operating temperatures consistently above 40°C can shorten motor lifespan by approximately 30%, and in severe cases, can directly burn out the windings. Overload is the primary cause of overheating. When the motor load exceeds its rated specifications, the BLDC motor controller outputs a larger current to maintain the speed, causing the windings to heat up rapidly. For example, when the load arm of an industrial robot becomes stuck, the motor is prone to overload, resulting in overheating and automatic shutdown.
Failure of the cooling system should not be ignored. If the cooling fan is damaged, the heat sink is excessively dusty, or the motor is installed in a confined environment, the heat generated during operation cannot be dissipated in time, accumulating in the windings and controller. Additionally, rotor-controller mismatch and abnormal voltage can also cause overheating. Excessive voltage increases the motor load, while insufficient voltage reduces motor efficiency, indirectly leading to increased heat generation. To address this, first reduce the load or adjust the operating cycle, clean the cooling components to ensure ventilation, and use instruments to test the voltage and current to ensure they meet the motor's rated parameters. If necessary, replace the BLDC motor controller with a compatible one.
III. Mechanical Failures: Noise and Vibration Accompanied by Performance Degradation
Mechanical failures in brushless DC electric motors often manifest in the bearings and rotor, typically presenting as noise, vibration, and unstable speed. As a core rotating component, bearings experience grease depletion over time, leading to wear, play, and even breakage. This not only increases rotational resistance but also produces regular abnormal noises. If the motor wheel feels loose when manually turning it laterally, it's highly likely a bearing problem; in severe cases, bearing fragments can even jam the motor.
Rotor failures also cause mechanical abnormalities. If the rotor magnets become loose or shifted, the motor will emit a "clicking" friction sound during rotation, and there will be noticeable jamming when manually turning it. Demagnetization of the magnets will lead to decreased motor power and increased power consumption; this problem is more likely to occur in high-temperature environments. Furthermore, uneven rotor mass distribution can cause unbalanced rotation, resulting in severe vibrations, especially in high-speed equipment, where this vibration can be transmitted throughout the entire machine. To solve these problems, the bearings need to be lubricated regularly and replaced promptly if damage is found; the motor needs to be disassembled to check the condition of the magnets, loose magnets should be re-bonded, and the rotor needs to be replaced if demagnetization is severe.
IV. Circuit Faults: Hidden Yet Fatal
Circuit system faults are highly concealed, yet can directly lead to motor failure. They primarily focus on the windings and drive circuits. Winding faults include short circuits and open circuits, often caused by aging or damage to the coil insulation or loose connections. A winding short circuit causes a sharp increase in current, resulting in localized high temperatures; a winding open circuit directly cuts off the path for generating electromagnetic torque, preventing the motor from operating. During testing, the BLDC motor controller can be disconnected, and the motor manually rotated. If the rotation resistance is abnormal, it is highly likely a winding fault.
Drive circuit faults are also common. Core components such as MOSFETs and motor driver ICs are prone to damage from overcurrent or overvoltage. Power surges may burn out the driver chip, causing the motor to lose response and protection signals. In addition, worn or corroded phase wires, as well as poor contact in Hall signal lines, can interrupt circuit transmission. During troubleshooting, use a multimeter to check continuity, replace faulty components, resolder loose connectors, and strengthen circuit protection to prevent future wear.
V. Control and Signal Interference: Causing Operational Disorders
As an electronically commutated motor, the BLDC motor is highly dependent on control signals; abnormal signals can lead to operational disorder. Besides Hall sensor failure, electromagnetic interference is also a significant contributing factor. The electromagnetic field generated during motor operation, or interference from nearby high-power equipment, can affect the stability of the PWM signal and position detection signal, causing fluctuations in speed.
Incorrect controller parameter configuration can also cause problems. For example, improper dead time settings may cause both upper and lower bridge arms to conduct simultaneously, affecting not only speed but also potentially damaging drive components. To address this, shielded cables can be used to connect the sensors and controller to reduce interference; oscilloscopes can be used to observe signal waveforms, calibrate the commutation meter and parameter settings, and self-learning algorithms can be used to optimize rotor position recognition accuracy and improve signal stability.
Routine Maintenance
- Regular Cleaning: Remove dust and debris from the motor housing and cooling system to prevent buildup and impaired heat dissipation.
- Wiring Inspection: Check monthly for loose or corroded terminals and plugs, and replace damaged cables promptly.
- Parameter Calibration: Optimize driver parameters according to load changes to avoid prolonged overclocking or undervoltage operation.
- Environmental Adaptation: Avoid prolonged operation in high-temperature, high-humidity, and dusty environments; install protective devices when necessary.
- Regular Testing: Use professional equipment to test key indicators such as Hall effect signals, winding resistance, and bearing clearance to detect potential faults early.
Most BLDC motor failures are systemic issues, requiring a comprehensive assessment considering electrical parameters, mechanical structure, and environmental factors. Regularly inspecting winding insulation, cleaning the cooling system, and lubricating mechanical components, along with establishing a real-time monitoring system, can significantly reduce the failure rate. Mastering these troubleshooting techniques can reduce maintenance costs and fully leverage the high efficiency advantages of BLDC motors.
