The electric drive system accounts for about 10% of the vehicle's value and is the second most important component after the battery. In terms of electric drive, the roll-up height is in the interests of both OEMs and consumers. In order to make the electric drive system develop towards lightweight, high performance, low energy consumption and low cost, the integration of electric drive has gradually developed into a trend, and the drive assembly, power assembly and more advanced X-in-one technology route have been born successively.
At first, the electric drive system was like a plate of loose sand, showing a decentralized layout. The wiring harness and pipeline are lengthy, the layout is complex, and various shells and boxes occupy a lot of volume, which affects the efficiency and energy consumption of the electric drive system.
In 2018, the industry proposed the concept of drive assembly (electric drive three-in-one), which tried to integrate the motor, motor control unit and reducer, and replaced unnecessary housings, wiring harnesses, pipes and boxes with common parts. The distance between the individual components is closer, enabling a compact design. This not only saves energy, space and costs, but also increases power density and transmission efficiency. Until now, the three-in-one electric drive is still the mainstream solution, and the overall technology is relatively mature.
Some companies did not stop there, but conducted more in-depth research and proposed power assembly (charging and distribution three-in-one) technology. The same approach is used to integrate OBCs (on-board chargers), PDUs (high-voltage distribution boxes), and DCDC converters. The combination of the drive assembly and the power supply assembly becomes a six-in-one solution for electric drive, realizing technology iteration and making the advantages of electric drive integration more obvious in terms of energy consumption, space, cost and performance.
Subsequently, the electronic control system continued to move towards a high degree of integration. In 2021, the concept of "X-in-one" electric drive system was born. This technology was promoted by various car companies at the new car press conference, in fact, it is the integration of electric drive three-in-one, charging and distribution three-in-one, BMS (battery management system) / VCU (vehicle controller) / PTC (positive thermistor) / TMM (thermal management controller) and other components, realizing the linkage and integration of the vehicle thermal management system, as well as the deep integration of mechanical components and power components.
At present, the electric drive system integration technology of some enterprises has broken through to more than seven in one, and the highest is ten in one.
As electric drive systems move towards a high degree of integration, so do challenges in terms of heat dissipation and maintenance.
First of all, the higher the integration of the electric drive, the closer the individual components in the system will be and the more concentrated the heat generated. It must have a stronger heat dissipation capacity to ensure that the internal temperature is normal, and upgrading air cooling to liquid cooling or direct cooling will achieve better results.
Secondly, multiple components are tightly connected by common parts, and once one of the components needs to be repaired, the entire module needs to be dismantled, increasing the cost and time of repair. Tesla's solution is excellent, and the housing of its fourth-generation electric drive system adopts a four-stage design, using bolts to connect the motor housing, the gearbox housing, the controller housing, and the control cover. Compared with integrated shells, the assembly, disassembly and maintenance processes designed with this split idea are more convenient, and at the same time, the redevelopment of complex integrated shells is avoided, saving costs and time. However, compared to the highly integrated X-in-1 technology route, it falls slightly short in terms of power density.
The integration of electric drives is the trend of the times. In the future, the powertrain module will continue to be deeply integrated and evolve into a highly integrated powertrain domain controller. Simple piping integration, circuit integration, and structural design will evolve into multiple sets of thermal management system integration, large-scale circuit topology integration, and multifunctional composite structure design. As the electric drive system continues to develop towards a high degree of integration, electric vehicles will achieve the goal of lightweight, energy consumption and performance will be better, and range anxiety is expected to be alleviated, and may even be completely solved.