1.Introduction
Brushless DC motor refers to a low-power DC motor with electronic commutation, also known as commutatorless DC motor and commutatorless DC motor. Structurally, it is equivalent to a reverse-mounted DC motor, with its armature placed on the stator and the rotor as a permanent magnet. Its armature winding is a multi-phase winding, generally three-phase, which can be connected in star or triangle. Each phase winding is connected to the transistor switch in the electronic commutator circuit.

2.The three main uses of brushless DC motors
1.Continuous load application: mainly in areas where a certain speed is required but the speed accuracy is not high, such as fans, water pumps, hair dryers, etc., such applications are low-cost and mostly open-loop control.
2.Variable load application: mainly in applications where the speed needs to change within a certain range, and there are higher requirements for motor speed characteristics and dynamic response time characteristics. For example, dryers and compressors in household appliances are good examples, and oil pump control, electric controllers, engine control, etc. in the automotive industry, the system cost of such applications is relatively higher.
3.Positioning applications: Most industrial control and automatic control applications belong to this category. In such applications, energy is often transmitted, so there are special requirements for the dynamic response of the speed and torque, and the requirements for the controller are also high. Photoelectric and some synchronous devices may be used for speed measurement. Many process control, mechanical control and transportation control belong to this category.

3.Common faults of brushless DC motors
1.Circuit failure: This may include unstable power supply voltage, poor circuit connection or damaged capacitor, resulting in the motor failing to start or unstable operation. Solving these problems usually requires checking the circuit connection, power supply voltage stability and whether the capacitor is damaged.
2.Mechanical failure: Due to damage or wear of the mechanical parts inside the brushless motor, it may cause uneven rotation or strong noise. Solving such problems usually requires cleaning or replacing damaged parts.
3.Sensor failure: Brushless motors rely on sensors to control speed and position. If the sensor is damaged or poorly connected, it may not be able to accurately control the motor. Solving such problems may require recalibrating the position sensor or replacing the speed sensor.
4.Driver failure: The driver is an important part of the brushless motor. If there is a failure, such as power supply problems, fuse damage, or current sensor failure, the motor may be uncontrollable or lose power. Solving such problems may require checking the driver power supply, replacing the fuse or current sensor.

4.Selection requirements for brushless DC motors
1.Voltage and current selection: First, the rated voltage of the brushless motor needs to be selected according to the power supply voltage to ensure that the voltage parameters of the motor driver match the power supply voltage. At the same time, the appropriate peak current should be selected. Generally, the peak current should be greater than or equal to twice the rated input current to ensure that the motor can operate normally under various working conditions.
2.Working environment adaptation: Consider the working environment of the motor, such as temperature range (-20? to 60?), humidity, whether waterproofing is required, etc. Select a motor model that can adapt to a specific working environment to ensure that the motor can operate stably under harsh conditions.
3.Insulation requirements: In order to ensure the normal operation of the brushless driver, attention should be paid to the requirements of power supply insulation. The insulation resistance between the Hall wire ground wire and the DC brushless motor winding wire, and between the Hall ground wire winding wire and the housing should be greater than 100 megohms 500VDC, and can withstand a 600VAC/50Hz/1mA/1 second withstand voltage test without breakdown.
4.Size and accessories selection: Select the maximum outer diameter, height, shaft diameter and other size parameters of the motor according to your needs. If necessary, you can also consider whether accessories such as reducers are needed.
5.Type and power selection: Select the appropriate motor type according to the specific application scenario. For example, ferrite permanent magnet DC motors are economical and have low temperature rise, which is suitable for general applications; while Al-Ni-Co permanent magnet DC motors or rare earth permanent magnet DC motors are used in situations with higher performance requirements, small size, and high ambient temperature.

At the same time, choose the power of the motor reasonably to avoid waste caused by excessive power or overload damage caused by too little power.