With silicon carbide technology still at the forefront of the industry, Weilai's EDS three-in-one electric drive system has higher efficiency and better performance, which further improves the power and endurance performance of the whole vehicle from the core. This is also the original intention of Wei Lai's self-research on the whole stack since its establishment, and fundamentally grasps the key points of technology research and development.
In the electric drive system composed of motor, reducer and controller, Weilai has always adhered to the strategy of paying equal attention to permanent magnet synchronous motor and induction asynchronous motor. Weilai's model is equipped with a combination of 160kW permanent magnet synchronous motor and 240kW induction asynchronous motor. However, with the technological upgrading of the second generation electric drive platform, its power will increase to 180kW and 300kW, which will directly improve the performance of the product. Behind this, I have to mention the black technology that was born in Nanjing, an advanced manufacturing center.
The word SiC is believed to be mentioned more and more in recent years. As the most typical third generation wide band gap semiconductor material, it has the advantages of fast switching speed, high turn-off voltage and strong high temperature resistance. The motor controller designed with silicon carbide power devices can greatly improve the efficiency and power density of the permanent magnet synchronous motor drive system, especially in the urban commuting scene. So Weilai introduced a new silicon carbide module for the first time. Compared with other friends, the full-stack self-research is six months to one year ahead of schedule, and the advantages of silicon carbide are further exerted.
For example, for multi-objective optimization, Weilai's high-speed drive circuit design uses smaller loop inductance and stronger drive chip to achieve faster switching speed. Moreover, its efficiency control strategy reduces the switching loss of discrete PWM scheme with variable switching frequency by 35% and 33.3% respectively, and the modulation optimization strategy can effectively improve the system power by 5- 10%. With the addition of these three technologies, the electric drive efficiency can be improved in an all-round way, the switching speed is faster, the power loss is smaller, and the CLTC working efficiency of the main drive motor can exceed 9 1.5%.
Therefore, the application of 180kW permanent magnet synchronous motor silicon carbide module reduces the comprehensive loss of electronic control system by 4% ~ 6%, and improves the power consumption performance of ET7 under urban working conditions. The application of silicon carbide devices in the main drive can also improve the endurance of electric vehicles. In addition, the new generation of electric drive system is more resistant to high temperature, and the maximum current capacity of the same volume is increased by more than 30%, which is suitable for working in a wider voltage range and has better expansion compatibility.
At the same time, compared with 160kW electric drive system, ET7 further improves NVH effect, further reduces the comprehensive working condition noise in the vehicle and brings a quieter driving experience through the modal optimization of EDS assembly with suspension fusion control, the non-uniform air gap and high positive air gap magnetic density of the motor, the optimization design of gear shaft structure, the harmonic injection of the controller and the optimization of control strategy.
Therefore, for the two motors mentioned above, the controller current of the first 180kW permanent magnet synchronous motor is increased, and the electromagnetic scheme of the motor and the speed ratio of the reducer (from 9.57 to 10.48) are optimized to obtain higher wheel end torque. After 300kW asynchronous induction motor, the current capacity of the controller is also improved, the electromagnetic scheme of the motor is optimized, the output torque of the motor is increased, and ET7 accelerates for 3.9 seconds. With the delivery of ET7, these two engines will be officially launched in Q 1 next year.
The new challenge of heating batteries and NVH is not only performance and efficiency, but also the performance of batteries and motors in cold winter weather. At this point, Wei Lai also made special consideration.
In view of the weak low-temperature performance of the battery, by developing special functions and optimizing the use of the low-temperature waste heat of the motor, the motor system can provide the maximum heating power of more than 4kW, which is equivalent to four household heaters, so that the battery is always at the most suitable working temperature, and better performance and endurance can be obtained at low temperature. Although 4kW doesn't seem like much, it's not easy to recover waste heat. The electricity saved can save more energy for active heating.
On the other hand, the application of this function also brings new challenges to NVH. As mentioned above, at the beginning of EDS development, measures such as optimization design of vehicle system, matching of dynamic and static stiffness of suspension system, coupling of EDS mode and chart were taken. Ensure that the overall architecture of EDS achieves the best NVH performance. At the same time, EDS module also uses software harmonic control algorithm to eliminate noise under heating conditions.
Specifically:
-Non-uniform air gap, high magnetic density in forward rotation of the motor: the motor can improve performance, balance electromagnetic radial force through electromagnetic optimization (non-uniform air gap), and optimize torque fluctuation through forward rotation of the air gap to achieve the best NVH performance.
-Precise optimization design of gear tooth profile and tooth direction: Through precise machining of gears in ET7 electric drive system, under the premise of mass production, micron-level precision control is realized, which makes the gears mesh more tightly when the vehicle works, improves transmission efficiency, reduces noise and further optimizes NVH performance of ET7.
-Harmonic injection algorithm iteratively optimizes noise jitter: after calculating harmonic voltage, the iterative optimization harmonic suppression algorithm uses harmonic voltage to better compensate the voltage, which reduces the electromagnetic noise generated by the motor and the overall noise of the electric drive system by 5~ 15dB, and provides users with a quieter driving environment.
With this series of black technologies, Nanjing Advanced Manufacturing Center of Electric Drive System has made an advanced electric drive system in Nanjing. Here witnessed the birth of Weilai manufacturing system, which was established on 20 15. The early trial production, body-in-white and vehicle test of Weilai ES8 were completed here as early as 20 17. Up to now, it has invested 250 million yuan and has 2 15 patents.
At present, the electric drive advanced manufacturing center covers an area of 528 mu, and the planned electric drive assembly capacity is 320,000 units/year, so as to build an electric drive with electrification, light weight and intelligence. It is one of the largest manufacturing bases for core components of new energy vehicles in the world. Advanced manufacturing of electric drive system includes 240kW electric drive system workshop, 160kW electric drive system workshop and PEU production line.
The two workshops of EDS_ cover 20,000 square meters and 25,000 square meters respectively. They are equipped with ABB six-axis machine, ABB seven-axis machine and AGV_ animal feed traction system, with flexible and dynamic production capacity. Full dynamic production is adopted for copper bar assembly, laser welding, turning dynamic balance, wire embedding, constant temperature electric heating, paint dipping, glue coating and online dynamic performance testing.
The Pe production line is equipped with the controller of the core component of the electric drive system, and the automation degree of ——IGBT coil curve, the core of the production line, is as high as 90%. The annual output of controller assembly line is 200,000 units, and the annual output of crimping line is 300,000 units. The whole production line integrates several processes such as tightening, press-fitting, leak detection and electrical testing. At the same time, it is a flexible assembly line, which can be compatible with the production of many types of products and can better control the production cost.
The advanced nature of the manufacturing center is reflected in the world's leading production, assembly, winding and other processes. It adopts a low-humanization, digital and automatic design, uses a high-precision six-axis robot with high-definition vision to take photos and position, and uses the world's largest laser generator of the same type, a special integrated winding machine, an automatic machine tool and a dynamic balancing machine for precise interaction, thus further realizing the intelligence, integration and visualization of production and improving the accuracy, efficiency and safety in the manufacturing process. Ground source heat pump technology can also realize the temperature regulation in the factory building, and photovoltaic panels are used on the roof, which can maximize the use of natural energy, save energy and reduce emissions, and be green and intelligent.
Che Yun concluded that Weilai ET7 can bring us the maximum power of 480kW, the peak torque of 850Nm, the acceleration of 100 km in 3.9 seconds, and the battery capacity selection of 75/ 100/ 150kWh, among which the application of silicon carbide and the whole EDS system naturally contributed. For Wei, who took the lead in testing silicon carbide, everything is in the upcoming ET7.
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