The electric drive system mainly consists of three parts: motor, motor control unit, and reducer.
Most of the time, user needs determine the direction of product technology evolution.
The core requirements people have for power units are nothing more than:
① The response must be fast, and the momentum must be strong;
② It should be highly efficient and energy-saving;
③Low failure rate, robust and durable, stable and reliable.
More potential demand lies in:
① The integration is high enough to free up more space in the car interior and front and rear trunks;
② The cost is reasonable (which will ultimately be reflected in the car price);
③ Avoid loud whistling at high speeds;
The diagram below summarizes the core elements of an electric vehicle's power unit. In fact, the technology and evolution of electric drive systems revolve around these aspects.
1. The electric motor power is currently sufficient, and there is little potential or necessity for further exploitation.
In terms of the most important attribute of electric drive, "power" , most electric vehicles currently have an excess of power. For example, the Tesla Model 3 Pro, priced at 360,000+ RMB, can outpace a performance gasoline car priced at around 2 million RMB in acceleration. The Wuling Hongguang Mini EV, priced at 30,000 RMB, is even more direct in its acceleration from a standstill than many gasoline cars.
In other words, electric motor power is sufficient for most electric vehicles currently, and the high horsepower premium of traditional gasoline vehicles has become worthless in electric vehicles. The high power density motors listed in the image above give the impression that the horsepower of electric vehicles is practically free...
Instead of investing heavily in developing new powertrain platforms to improve power parameters on top of the already sufficient motor power, automakers would be better off distributing the costs to other areas where users can more readily perceive the difference.
Of course, for a few performance electric vehicles that pursue absolute power acceleration, such as the Tesla Model S Plaid, Lucid Air Sapphire, Hummer EV, and Porsche Taycan Turbo S, etc.
This involves some key new technologies for enhancing power:
Methods such as using flat winding coils, improving slot fill factor through end transposition, and optimizing rotor structure can improve magnetic fill factor, thereby further increasing motor power and power density.
In recent years, more and more car models have been equipped with waterfall-style oil-cooled motors, which make motor cooling more efficient and help power output remain continuous without decay.
Some systems also use intelligent algorithms to optimize motor power output, resulting in better power, energy consumption, and stable handling.
Personally, I think the technologies mentioned above are all core technologies of electric drive!
2. Motor energy efficiency has reached its limit; improving energy efficiency will depend on the application of silicon carbide.
Based on Part 1, which states that the motor power is sufficient or even excessive for most users, the following figure is an energy efficiency map of a certain motor. It can be clearly seen that the motor's energy efficiency is above 90% in most daily use speed ranges.
Moreover, most new energy vehicles currently have motors with an optimal energy efficiency of 90% to 95%, and some high-efficiency motors even reach 96%. At this point, if you want to further improve the energy efficiency of the motor on the existing basis, the cost will increase exponentially, which is not very cost-effective for car manufacturers and users.
△ Energy efficiency MAP of a certain motor
Therefore, improving the energy efficiency of the main inverter in the motor control unit has become a new direction for improving the energy efficiency of the entire electric drive system.
This means replacing the current mainstream IGBT modules with SiC silicon carbide modules!
△ Advantages of silicon carbide materials
Silicon carbide (SiC) MOSFETs have many advantages, including small size for easy packaging and integration, fast switching/conduction response with lower losses, high voltage withstand (10 times that of silicon-based MOSFETs), high thermal conductivity for easy heat dissipation, and higher power density.
△ Analysis of the Advantages of Silicon Carbide
Most importantly, the motor control unit using SiC (silicon carbide) modules can achieve an efficiency improvement of about 5% from the battery to the motor compared to the IGBT module solution, which means it can save about 5% of the energy consumption of the whole vehicle.
Compared to the battery costs associated with an additional 5% range for automakers, and the negative impact of increased vehicle weight, even silicon carbide modules, which currently have a higher cost than IGBTs, are the best choice!
In addition, compared to IGBTs, silicon carbide has the advantage of being more resistant to high voltage (above 1000V), making it more suitable for the 800V electrical architecture that more new energy vehicles will be equipped with in the future. It can be used not only in main inverters, but also in high-voltage charging piles, high-voltage battery packs, OBC chargers, and DC-DC converters, and will have a wider range of applications, which can further improve the energy efficiency of the whole vehicle and the charging experience!
△ Application of silicon carbide devices in new energy vehicles
Special praise goes to the domestic brand BYD. BYD is the only car company in the world that has achieved self-developed and self-produced silicon carbide devices!
3. Integration has great potential and is an inevitable trend. Cross-system integration capability will be the core technological competitiveness, resulting in higher user value!
The above mainly discussed the upgrading and optimization of individual components of the electric drive system. The integration of multiple components into a single unit is now an industry trend!
Highly integrated electric drive systems offer many advantages:
Significantly reduces volume and weight, lowers overall BOM cost, improves integrated assembly efficiency, and increases the overall power density of the electric drive system, etc.
The value to users lies in the fact that the smaller size saves more layout space, resulting in a larger interior space and front and rear trunk volume; the reduced weight means a longer driving range with the same amount of electricity; at the same time, the reduced cost of BOM also indirectly reduces the user's purchase cost.
The evolution of electric drive systems can be roughly divided into three stages:
From 2015 to 2017, the three separate components became the mainstream in 2018 to 2020, and from 2021 to the present, it has entered the stage of multi-in-one integration.
The diagram below outlines the evolution of electric drive systems, making it more intuitive and easier to understand!
△ Evolution path of electric drive systems
Although all-in-one systems are simply combinations of components from multiple systems, cross-component and cross-domain system integration is a true test of technical and engineering capabilities, and currently only a few large manufacturers with accumulated experience can achieve this.
Compared to motor power enhancement and energy efficiency optimization, the comprehensive benefits brought by multi-functional integration are more obvious, making it one of the most important core technologies for electric drive systems in new energy vehicles.
