What are the big three electrics and small three electrics of the electric drive system?

Generally speaking, the three major electrics include: drive motor, electronic control, and transmission; the three small electrics include: high-voltage distribution box PDU, on-board charger OBC, and DC/DC converter.

1. The three major electric components include:

Drive motor assembly

Controller assembly

Transmission assembly

The electric drive system of new energy vehicles, in a complex working environment of high temperature, high humidity and vibration, uses a real-time response software algorithm to accurately control the power output characteristics of power electronic components at high frequency to achieve control of the drive motor, and ultimately transmit power to the outside through precision mechanical parts. 2. The small three electrics also include three assemblies:

DC/DC Converter

On-Board Charger (OBC)

High-voltage power distribution box PDU (Power Distribution Unit)

Its main function is to provide power conversion and battery charging and discharging functions. As an important part of the powertrain of new energy vehicles, the on-board power supply must meet the characteristics of high power density, small size, light weight, strong anti-interference ability, strong reliability, and long life. 2. Key technologies of electric drive 1. High-speed motor The drive motor is mainly a mechanical component. In the context of increasingly fierce competition in the industry, improving the power-weight density and power-volume density of the motor and reducing the weight of the motor are effective ways to reduce the cost of drive motor products. Increasing the motor speed puts higher requirements on the design of the motor. Bearing selection, motor heat dissipation, shaft material, stator and rotor silicon steel sheet material, electromagnetic simulation, mechanical strength simulation, thermal simulation, tolerance calculation and matching, etc. have become more challenging. In recent years, the maximum speed of motors has been constantly improving, whether for domestic or foreign products.

2. Flattened motors Flat wire motors are motors with flat copper-coated wire winding stators. Compared with ordinary round enameled wire windings, flat wire windings have higher energy density and higher motor efficiency at the same volume. Its advantages include: Higher slot fill rate: Compared with traditional round wire motors, the bare copper slot fill rate can be increased by 20-30%, effectively reducing winding resistance and copper loss. Better heat dissipation performance: The flat wire shape is more regular, fits tightly in the stator slot, and has higher heat conduction efficiency, which improves the peak and continuous performance of the motor. Shorter end size: Compared with the round wire motor winding end size, the total height of the end is 5-10mm shorter, which effectively reduces the copper loss of the end winding. Better NVH performance: Flat wire structure windings have better rigidity. At the same time, the flat wire windings are inserted through the core end, and a smaller notch design can be selected in the electromagnetic design to effectively reduce the cogging torque pulsation. Tesla, SAIC New Energy, Chevrolet Volt, Toyota's fourth-generation Prius, Great Wall Honeycomb, Dongfeng Lantu, Porsche Taycan, Volkswagen ID.4, Han GT, Geely Zeekr and other models or platforms all use flat copper wire stator motors. Flat wire motors have entered the large-scale mass production stage. In the future, as the technology and process become more mature, the production cost of flat wire motors is expected to be lower than that of traditional round wire motors.

3. IGBT single-tube parallel discrete technology The IGBT module is a modular semiconductor product formed by packaging IGBT (insulated gate bipolar transistor chip) and FWD (freewheeling diode chip) through a specific circuit bridge. The packaged IGBT module is directly used in inverters, UPS uninterruptible power supplies and other equipment, and is widely used in rail transit, smart grids, aerospace, electric vehicles and new energy equipment. The power module is made based on the concept of MOSFET and IGBT single-tube parallel technology (PEBB power electronics integration technology), which is conducive to flexible capacity expansion of motor controllers, precise power matching, cost reduction, product reliability, and good electromagnetic compatibility. According to Inbo's 2021 semi-annual report, its "integrated core" powertrain with a single-tube parallel solution has a weight, volume, and cost that are more than 20% lower than current mainstream products.

At the same time, as motor controllers develop towards high voltage and high power, the application of the third-generation power semiconductor SiC has become a consensus. Due to its low on-resistance and fast switching speed, the single-tube parallel technology can bring out its optimal characteristics. 4. SiC improves electronic control performance In new energy vehicle motor controllers, power conversion is achieved by controlling the switching of IGBTs. Due to the limitations of the material itself, IGBTs are difficult to operate above 200°C. High-power density motor controllers require efficient power conversion efficiency and higher operating temperatures, which also puts higher requirements on power devices, such as lower conduction losses, high temperature resistance, and high thermal conductivity.

Power devices based on SiC single crystal materials have the advantages of high frequency, high efficiency, and small size (70-80% smaller than IGBT power devices), and have been used in Tesla Model 3. SiC semiconductor controllers can enable new energy vehicles to achieve longer driving range, shorter charging time, and higher battery voltage. Compared with the second-generation silicon-based IGBT, the energy efficiency of semiconductor SiC 750V increases by 8-12%, the total loss is reduced by about 1/7, the module volume is only about 1/5 of that of IGBT, and the switching frequency is 5-10 times that of IGBT. 3. Development trend of electric drive assembly technology 1. System integration System integration is a deterministic trend and is a choice under technological development and cost pressure. The integration of electric drive systems is a definite trend in the future. At the same time, integrated products also increase the entry barriers of the industry. From a technical perspective, the advantages of products with a higher degree of integration include: Mechanically, the housing, shaft and other components can be integrated, which reduces the number of parts used and the weight of the components, saving costs; Electrically, the integration of the three major electrical systems can reduce the length of the three-phase line connecting the controller and the motor, which improves efficiency while also saving wiring harness costs, and improves electromagnetic compatibility performance in a closed housing space; the common circuit board design of the three minor electrical systems can also reduce costs and product size. At the system level, integrated products can be supplied by one company and can be optimized and designed at the very beginning to achieve the optimal system cost, saving costs while also saving space, and making vehicle assembly faster and more convenient.

In 2018, the total price of the split-type 90kw electric drive system motor, electronic control, reduction box, and high-voltage connection harness was about 11,000 yuan; in 2020, the average product price of the integrated 90KW electric drive system has dropped to about 7,500 yuan, a decrease of more than 30%, and the volume and weight have also dropped significantly. 2. All-in-one will gradually replace three-in-one With the further improvement of the integration of electric drive products, in addition to motors, motor controllers, and reducers, high-voltage junction boxes, DC/DC, charger OBC and other components may also be integrated to form a more functional all-in-one powertrain system.