Key Technologies for Drive Motors
The key technologies of drive motors mainly include motor design and optimisation, control algorithms and systems, sensor technology and power electronics development. This paper describes the key technologies for the development of drive motors from flat-wire motors, oil-cooling technology and all-in-one electric drive systems.
(1) Flat wire motor
Flat wire motor compared with the traditional round wire motor, bare copper slot full rate can be increased by 20% -30%, the total copper consumption decreased by 21%, efficiency increased by about 1%. Slot full rate of improvement is equivalent to the motor in the same volume of conditions, can output higher power and torque; or power under the same conditions, can reduce the motor's outer diameter and volume, and thus reduce the weight of the motor, so flat wire winding motor has a higher power density, can make permanent magnet motor continue to develop in the direction of smaller.
(2) Oil cooling technology
Three commonly used motor cooling systems: air-cooled, liquid-cooled, evaporative cooling and additional thermal paths to enhance the heat dissipation system is.
Air-cooled heat dissipation system: With the advantages of low cost, high reliability and easy installation, it is widely used in the field of heat dissipation of small power motors.
Liquid-cooled heat dissipation system: with high heat dissipation power, it is suitable for heat dissipation occasions with high heat generation and high heat flow density of the motor, but liquid-cooled heat dissipation system needs additional circulating liquid circuit and sealing system, which increases the cost and complexity of the motor system.
Evaporative cooling system: mainly used in megawatt-class large-capacity generator set cooling system, the use of gas-liquid phase change cycle to achieve efficient cooling of the motor.
The winding end of permanent magnet synchronous motor generates a large amount of heat, the cooling liquid cannot directly contact the winding under water-cooling method, and the cooling oil can directly contact the winding under oil-cooling method, which has higher cooling efficiency and more prominent advantages.
The cooling oil of oil-cooling technology can directly contact with the motor's heat-generating parts, and the cooling efficiency is much higher than that of traditional water-cooling cooling system. Moreover, the oil medium has the advantages of good insulation, high dielectric constant, low freezing point and high boiling point. The drive motor of BYD DMI adopts direct-injection rotor oil cooling technology, which can increase the power density of the motor by 32%.
