Research status of electric vehicle drive motor cooling structure 2
Liquid Cooling Structure
The liquid-cooling heat dissipation structure is a motor cooling solution in which a sealed circulation flow channel is designed inside the motor casing or inside the motor, and the cooling medium exchanges heat through cooling structures such as the casing water jacket, stator channel, and rotor channel. According to the cooling medium, liquid cooling heat dissipation structures can be divided into two categories: water cooling heat dissipation and oil cooling heat dissipation. Liquid cooling solutions are suitable for applications such as high-power motors where cooling requirements cannot be met through natural heat dissipation. The most commonly used high heat capacity liquid cooling media in liquid cooling solutions are water, ethylene glycol and transformer oil.
In order to improve the shortcomings of the water medium with high freezing point and low boiling point, a water-ethylene glycol mixed solution is usually used during use to lower the freezing point of the medium and improve the overall environmental adaptability of the water-cooled heat dissipation system. In addition, the water-cooled heat dissipation system is prone to scale corrosion during long-term operation, so anti-corrosion and anti-foam additives should be added during use.
Taking an asynchronous motor equipped with a water-cooled cooling jacket as the research object, the temperature field distribution and inlet and outlet pressure drops of the motor under different numbers of channels are analyzed, as shown in the figure. Experimental results show that increasing the number of channels or increasing the flow rate will reduce the maximum temperature of the motor, while the required pump power will also increase. In addition, the study found that the multi-port system was of no real use in reducing the maximum temperature of the motor. The overall maximum temperature of the multiport is higher compared to the dual-port configuration under the same operating conditions.
Although the cooling water jacket provides sufficient heat transfer to the active part of the stator winding, it is usually not sufficient to dissipate the heat from the end windings and the rotor due to the high thermal resistance between the heat source and the cooling medium. Therefore, this cooling structure is not suitable for motors with long end windings. For this type of motor, a special cooling structure can be designed for the severe heating part to meet the cooling needs of the motor.
