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What are the common faults of BLDC motor used in indoor air-conditioning units?
Release Date:
2025-10-15
The failures of BLDC motor used in indoor air-conditioning units mainly occur in three core modules: the electronic commutator, the position sensor, and the mechanical components. The following is a detailed analysis of common faults, their manifestations, and their causes:
The failures of BLDC motor used in indoor air-conditioning units mainly occur in three core modules: the electronic commutator, the position sensor, and the mechanical components. The following is a detailed analysis of common faults, their manifestations, and their causes:
Electronic Commutator (Driver) Fault
Symptoms: The motor fails to rotate, its speed fluctuates erratically, a fault code is displayed upon power-up (e.g., an E-series error on the air conditioner display), and in severe cases, a burning smell may be detected.
Core Causes
Voltage fluctuation or lightning strike causes the power switching device (IGBT/MOSFET) to break down, making it impossible to control the energization of the stator winding;
Capacitor aging and bulging on the control circuit board leads to unstable power supply;
High temperature and high humidity environments can cause oxidation and short circuits in circuit board solder joints.
Typical scenarios: Vm is unstable during the summer peak electricity consumption period, and the drain pipe of the indoor unit of the air conditioner is blocked, causing condensation to seep into the motor control box.
Position sensor (Hall sensor) failure
Symptoms of failure: difficulty starting the motor (requiring multiple power cycles before it rotates), uncontrolled speed, vibration at low speeds, and in sensorless models, the motor may fail to start altogether.
Core Causes
The Hall element itself has aged and failed, rendering it unable to accurately detect the rotor magnetic pole position;
The connection wiring between the sensor and the electronic commutator is broken or has poor contact;
Excessive dust inside the motor has coated the sensor, interfering with magnetic field signal acquisition.
Typical scenarios: Failure to clean the air conditioner filter for an extended period allows dust to enter and accumulate inside the motor; improper wiring during installation can cause connectors to become loose.
Mechanical Component Failure
Bearing wear / Lubrication failure
Fault symptoms: During operation, a “buzzing” abnormal noise or a “rustling” friction sound is emitted; the noise increases with higher rotational speed, and in severe cases the rotor may seize.
Causes: Drying out of the bearing’s internal grease (common after 2–3 years of normal operation), ingress of dust into the bearing clearance leading to wear, and prolonged high-load operation of the motor causing deformation of the bearing balls.
Demagnetization of Rotor Permanent Magnets
Symptoms: Reduced motor torque, inability to increase air-conditioning fan speed, and abnormal current rise under full-load operation.
Cause: The motor has been operating for an extended period in a high-temperature environment (e.g., dust accumulation on the air-conditioner heat exchanger resulting in poor heat dissipation) or has sustained a severe impact, leading to magnetic degradation of the permanent magnets.
Stator Winding Fault
Fault symptoms: motor trips upon startup and shuts down due to overheating during operation; multimeter measurement reveals abnormal winding resistance (open circuit or short circuit).
Causes: Short circuits resulting from aging and damage to the winding insulation; moisture ingress leading to winding dampness and leakage current; and compression or breakage of winding leads during installation.
Control Signal Communication Fault
Fault symptoms: The motor does not respond to the air conditioner remote control’s fan-speed adjustment commands, or it can only maintain a fixed speed.
Core Causes
Poor contact in the communication line between the air conditioner’s main board and the motor driver;
The speed control signal (0–10 V analog signal/PWM pulse) is abnormal, such as electromagnetic interference on the signal line or Vm deviation beyond the threshold.
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