‌Axial flow fans are widely used in many fields, including industrial, commercial, residential and special environments‌. Industrial Applications: In chemical, electricity, steel and other industries, axial flow fans are used to discharge dust, gas and smoke, providing workers with a clean working environment. In environments with dense equipment or high heat generation, such as computer rooms and factory workshops, axial flow fans help heat dissipate and cool down to ensure the normal operation of the equipment. Axial flow fans are also used for control of large equipment and machines, as well as provide ventilation and air circulation to smooth the airflow. ‌Commercial and Residential Applications‌: Axial flow fan can be used for ventilation in general factories, warehouses, Offices and residences, improving indoor air quality and improving comfort‌ 2 3 . In humid environments, axial fan accelerates air flow, reduces humidity, and reduces the impact of moisture on items and the environment‌ 2 3 .

The main features of axial flow fans include: large flow rate, small air pressure, small size, light weight, simple structure, high fan efficiency and wide working range. Specifically: Large flow rate and small air pressure: The axial flow fan can generate a larger air volume, but its air pressure is smaller than that of the centrifugal fan. Small size and light weight: The axial flow fan can be greatly reduced in volume, cover a small area, and is light in weight under the same flow rate. Simple structure: The structure of the axial flow fan is relatively simple, which helps save metal and processing time, and also means that maintenance may be relatively easy (although some point of view are mentioned that the air mechanism is complex, this may be not a common phenomenon for a specific type or design axial flow fan). High fan efficiency: After adjusting the rotation of the blade, the axial flow fan can work in the new optimal working area to maintain high efficiency. Wide working range: The efficient working area of ​​the axial flow fan is wider than that of the centrifugal blower, so its working range is relatively wide. In addition, the axial flow fan also has different characteristics according to the type of motor. For example, the AC axial flow fan driven by an AC motor has the characteristics of simple structure and low price; the DC axial flow fan driven by a DC motor has the characteristics of small size, light weight and high efficiency; while the EC axial flow fan driven by a permanent magnet motor has the characteristics of high efficiency, energy saving and environmental protection. 6 . These different types of axial flow fans are suitable for different application scenarios and requirements.

The working principle of a three-phase external rotor motor is based on the principle of electromagnetic induction, and the rotor is driven to rotate through the rotating magnetic field generated by the three-phase alternating current. Specifically, when a three-phase AC power supply is applied to the stator coil of the three-phase external rotor motor, a rotating magnetic field will be formed. This rotating magnetic field is formed by superposition of the magnetic fields generated by the three-phase current in the stator coil, and its rotation speed is related to the power supply frequency and the number of poles of the stator winding. Since the rotor of the outer rotor motor is located outside the stator, the conductor circuit in the rotor is passed through by a rotating magnetic field. When the rotating magnetic field cuts the rotor conductor, an electromotive force is induced in the conductor, thereby generating an induced current on the conductor. This induced current forms another magnetic field in the rotor, interacting with the rotating magnetic field to generate electromagnetic force. This electromagnetic force acts on the rotor shaft, forming an electromagnetic torque, which drives the rotor to rotate in the direction of the rotating magnetic field. Therefore, the working principle of a three-phase external rotor motor can be summarized as: cutting the rotor conductor through the rotating magnetic field generated by the three-phase alternating current, inducing the electromotive force and current, and then generating electromagnetic force to drive the rotor to rotate.