The influence and control of fans on the thermal effect of motors

   Fan is an important wind pressure component of the motor ventilation and heat dissipation system, which compensates for the wind pressure loss of the cooling medium when it passes through the air path. It transports a certain flow rate of cooling medium to the heating part of the motor, takes away heat, and transfers it to the next level of cooling medium. Normally, the fan installed inside the motor cavity is called an internal fan, while the fan placed outside the motor casing is called an external fan. Both the internal and external fans are fixed to the motor rotor and rotate together with the rotor.

    For small and medium-sized motors, heat dissipation mainly relies on the external fan to generate wind pressure and the wind hood to guide the flow. By blowing the surface of the shell with the cooling medium air, the heat generated by the motor is carried to the surrounding environment. Generally, an external fan is installed at the non axial end of the motor, and it forms an external ventilation and heat dissipation system with the fan cover and the base heat dissipation ribs to ensure that a certain flow rate of cooling medium air flows through the surface of the shell to take away enough heat, forming a relatively stable temperature field from the internal heating element to the surface of the shell and from the shell to the surrounding environment space, and the maximum temperature field inside the shell is not higher than the design allowable value.

    For large and medium-sized motors, the internal air circuit structure is complex, which can easily cause local heat accumulation. Therefore, most iron cores are equipped with axial and radial ventilation channels, and internal fans are installed at one or both ends of the motor rotor to form an independent circulation system for the internal cooling medium air along a reasonable path. Installing internal fans at both ends is suitable for radial ventilation structure motors; If there is an internal fan at one end, it is used for axial and hybrid ventilation structure motors.

      As the wind pressure component of the motor ventilation and heat dissipation system, the fan, together with the motor's iron core, winding, etc., forms an independent ventilation and heat dissipation system that drives the internal cooling medium air to circulate along the designed preset path. For example, a radial ventilation cooling structure motor has at least three iron core sections, and adjacent iron core sections are equipped with ventilation grooves and form ventilation channels. The wind resistance of the ventilation channels gradually increases from both ends of the motor to the middle part of the motor, which can improve the balance of air flow through multiple ventilation channels, so that the temperature of the coil and multiple iron core sections is basically evenly distributed along the axial direction of the motor. Compared to solid structures, it significantly reduces the highest temperature value in the temperature field without changing the total flow rate of wind, effectively avoiding faults caused by excessive local temperature rise.