Importance of inverter technology to the growth of new energy vehicle market

- Electric vehicle inverter technology -

In the electric drive system of electric vehicles, the inverter plays a vital role. It receives the DC voltage from the battery as input and then inverts it into AC output, thereby driving the traction motor to power the vehicle.

Additionally, the onboard charging system acts as a rectifier, converting AC power to DC power, which has a significant impact on charging time. This onboard charging system is usually connected to a Level 1 or Level 2 charger, which is plugged into the vehicle to provide this AC to DC charging service.

In some cases, the onboard charger and inverter are combined into a single system to take advantage of the efficiency benefits of a high-voltage architecture, where thermal management of the charging system allows for greater power output, resulting in faster charging.

Key areas where the industry is working to reduce charging times include:

1. Increase vehicle battery voltage levels from 400 V to 800 V or higher. This increase allows the current to be reduced to achieve the same level of power generation with reduced energy losses.

2. Introducing Level 3 DC chargers. Since the AC-DC rectification is done outside the vehicle, more power can be delivered to the battery during charging.

DeLand said: "Our mission at GKN Automotive is to drive a more sustainable world, and efficiency gains are seen as key to our success. We want to innovate in the space so that these efficiency gains can improve coverage for the end customer and reduce electricity consumption on the grid."

Another focus is to leverage the company’s extensive experience in all-wheel drive (AWD) to differentiate electric drive systems for customers. The lateral dynamics products of AWD systems for internal combustion vehicles can be directly applied to electric vehicles to improve vehicle stability, traction and agility. This application can further enhance the performance and driving experience of electric vehicles.

- Integration -

In many early electric vehicles, the inverter and traction motor existed as two separate parts, and the AC power transmission between the two relied on heavy cable harnesses. However, by integrating the inverter into the electric drive unit (EDU), the cable harness is replaced with a busbar that establishes an internal connection between the inverter output and the traction motor input.

This integration significantly reduces system weight and reduces resistance between the inverter and traction motor, thereby improving efficiency and reducing heat losses.

In addition, because the inverter can be designed to fit the natural contours of the traction motor and gearbox, the entire unit becomes more compact. Finally, the cooling system between the inverter and the traction motor can be shared more easily, eliminating another possible redundancy. Key factors such as compatibility and integration of inverter technology are particularly important.

Modularity gives automakers the flexibility to choose the eDrive components they want to use while maintaining consistency in those specific features.

In summary, integrating the inverter into the electric drive unit has significant advantages in electric vehicle design. It can not only improve efficiency, reduce heat loss, and make the unit more compact, but also improve product compatibility and flexibility, providing more options for automakers.

- Use of wide bandgap semiconductors -

Compared to silicon IGBTs, silicon carbide has a higher switching frequency capability, which allows for higher motor speeds. This in turn leads to smaller traction motors and an overall reduction in the size of the electric drive system. As the motor speed increases, the gear reduction ratio in the gearbox can be increased in order to convert the higher speed into the necessary torque.

This way, the motor needs to produce less torque, allowing it to be smaller. However, the trade-off for this topology is a larger gearbox and greater noise, vibration and harshness challenges.

Another advantage of smaller motors is that they require less current to operate, making the power stage within the inverter more cost-effective. However, it is important to note that in this topology, the higher switching frequency creates more power losses in the inverter.

However, this is offset by the overall current reduction of the smaller motor. At the same control frequency, SiC MOSFETs are more efficient than traditional silicon IGBTs due to the faster switching slew rate of SiC, which reduces the negative impact of switching losses.