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　　Electric vehicles are gradually entering the market, and the manufacturing requirements for permanent magnet motors (PM motors) are getting higher and higher. With the development of permanent magnet motors, what are the special requirements for motor housings?

　　As a matter of fact, high efficiency and light weight are the development direction of electric motors. It is an important way to improve efficiency; at the same time, it light certain weight. When using aluminum alloy base and end caps, the weight can be greatly reduced. Of course, if there are better plastics or other materials in the future, it can not only achieve high strength and hardness, but also resist high temperature and aging; this will be another technological change.

　　The permanent magnet and stator-rotor core of synchronous motor are prone to generate a large amount of eddy current loss and harmonic loss, which are embodied in the form of heat energy, resulting in overall or local temperature rise of the motor, or even demagnetization of the permanent magnet, which seriously affects the operating performance and reliability of the motor. Therefore, permanent magnet synchronous motor has high requirements for heat dissipation, fully consider the heat dissipation requirements of permanent magnet synchronous motor when welding permanent magnet synchronous motor shell, and try to avoid heat dissipation. Otherwise, it is not conducive to the operating performance and reliability of the permanent magnet synchronous motor.

　　The motor cover has two functions, one is to prevent solids from immersing into the casing and to prevent personnel from contacting dangerous parts in the casing. The second is to control the air duct. Since the fan is self-cooling, if there is a cover, the cover will blow along the gap (circumferential distribution) between the cover and the radiator to the end, thus taking away heat from the radiator. If there is no cover, the wind from the fan has no direction and the cooling effect is poor.

　　The cooling method of synchronous motor is divided into external cooling and internal cooling, and external cooling is also called surface cooling. The cooling medium only touches the motor core, the winding ends and the outer surface of the motor casing. Heat must be transferred to these parts from the inside and then to the cooling medium by radiation.

　　External cooling of synchronous motors is primarily air-cooled, with air circulation usually driven by a fan. The main methods of external cooling include natural cooling, self-fan cooling and other fan cooling. Natural cooling motors for permanent magnet synchronous motors do not have special cooling devices. Due to the limited heat dissipation capacity, only the radiation on the surface of the parts and the natural convection of the cooling medium carry away the heat generated by the motor.

　　When the motor rotates, the wind pressure generated by the fan forces the air to flow and blow to the heat dissipation surface, which greatly improves the heat dissipation capacity of the motor. Self-cooling fans are divided into internal self-cooling type and external self-cooling type according to the fan. The internal self-cooling type is suitable for open motors. The internal fan is mounted on a rotating shaft inside the end cap. The fan rotates with the rotor and blows external cooling air into the machine, into the armature surface and through the axial and radial ventilation slots. Enclosed motors are suitable for externally self-cooling models. In addition to the internal fan, the motor is equipped with an external fan, which is on and end cover of the external rotor. With the help of the external fan, the heat from the motor housing radiates into the surrounding air. At this point, the internal fan can continue to accelerate the air circulation inside the motor, so that the temperature is evenly distributed and the heat is more easily transferred to the base.