High energy efficiency traction inverters help electric vehicles drive farther

Battery electric vehicles have become the developing focus of the automobile industry. However, increasing the driving distance of electric vehicles is the key for the masses to widely accept electric vehicles. This text will introduce high energy efficiency traction inverters used power devices launched by ON Semiconductor and help you comprehend their important role in electric automobile applications.

Traction inverters will become the developing key of the electric automobile market

Globally, new energy vehicles have become the developing focus of the automobile industry. According to the forecast by ON Semiconductor, the output of hybrid electric vehicles/electric vehicles (driven by pure battery electric vehicles, BEV) will increase with a compound annual growth rate of 20%. Based on different geographic locations, plug-in hybrid electric vehicles (PHEV) will have an increasingly important market position, while full hybrid electric vehicles will increase their output over the short term at a slower speed. Seen from the current growth rate, China will consume over 65% of all Battery Electric Vehicles (BEV) powertrains until 2025, such as traction inverters and other key components of semiconductor power devices, which will place pressure on the automobile supply chain.

Although the adoption rate of BEV is steadily growing, the rate is still slower than that of previous forecasts, which is mainly caused by two factors. First, the cost of BEV and plug-in hybrid electric vehicles is still higher than the equivalent internal combustion engine (ICE) vehicles. However, the forecast truly indicates that the ownership cost of BEV and internal combustion engine vehicles will reach cost parity in 2022 due to technical improvements and battery cost reduction. The second main stumbling block is normally called “range anxiety”, which means being anxious about the possibility that a BEV may run out of electric power before the end of the journey and thus cause drivers and passengers to be stuck. This is mainly caused by the capacity of the battery, but the availability of appropriate charging stations and the necessary charging time are also important.

Although increasing battery size (thus increasing capacity) is a choice for lengthening the vehicles’ endurance range, it is at the expense of vehicle cost and weight (the heavier the vehicle, the more the required energy). It highlights the importance of energy efficiency for BEV. Especially when using most electric powered powertrain systems, any slight improvement of energy efficiency can reduce kilowatt loss and thus helps the vehicle to use available energy for continuous driving.

One of the challenges of designing a BEV powertrain is that the battery provides direct current while traction motors need alternating current. The main traction inverter transforms the direct current provided by the automobile's high-tension battery in order to generate the torque for the vehicles to move forward, and provides the required alternating current for induction motors. Therefore, inverter efficiency in traction inverters is a key design consideration of the powertrain.

These inverters normally include 400V (HVL1) or 800V (HVL2) high-voltage battery systems, the latter of which has been increasingly popular in the latest designs. These systems require that the power semiconductor device should be in the range of 600-750V or 900-1200V, corresponding to HVL1 or HVL2. They also require that the power inverters work at the electric current level of 400-1000A for each phase. For this purpose, some manufacturers put discretely package devices in parallel and most of them use a power integration module (PIM).

To assist designers with designing these challenging power systems, ON Semiconductor recently launched a new VE-Trac™ power integration module product family that provides the best electric and thermal performance. ON Semiconductor has released two design platforms including the VE-Trac™ Dual used for high power density scalable extensible inverter solutions, and VE-Trac™ Direct used for widely adopted rapid product deployment.

VE-Trac Dual is a stackable and scalable dual-side cooled half-bridge module with a compact footprint to provide a small space platform solution used in  80kW-250kW applications. The first device launched was the NVG800A75L4DSC, with a nominal voltage of 750V and rated current of 800A, which is twice the power capacity of other devices on the market. The efficient dual-sided cooling of VE-Trac Dual ensures that it has the market-leading thermal performance. With wire-bond free internal structure, VE-Trac Dual provides three times longer module operation lifetime compared to wire-bond solutions. NVG800A75L4DSC has embedded smart IGBT to provide a rapid reaction time for integrated over-current and over-temperature protection functions, as well as providing a more robust solution. NVG800A75L4DSC is AQG324 qualified and released to production in November 2019.

Meanwhile, the VE-Trac Direct platform provides the best-in-class performance, including direct cooling to realize excellent thermal performance. VE-Trac Direct is housed in a highly integrated six-pack configuration, which is widely adopted by automobile original equipment manufacturers (OEM) and Tier-1 suppliers. The first VE-Trac Direct product - NVH820S75L4SPB - was rated at 750V 820A. It was qualified according to AQG324 standards and released to production in December 2019. Future VE-Trac Direct products from ON Semiconductor will provide multiple power classes suitable for inverter applications between 80kW to 180kW with mechanical compatibility. VE-Trac Direct platform will provide simple and rapid power scaling for multiple traction inverter power classes and applications.

All VE-Trac Dual and VE-Trac Direct products can achieve continuous operation with maximum junction temperature of 175ºC  to provide higher peak inverter output power in comparison to other products currently in the market. Devices of the future for the VE-Trac™ product family will include discrete power devices, isolated gate drivers, additional power modules, bare dies solutions, and wide bandgap (WBG) Silicon Carbide devices. All products in the VE-Trac product family will have improved performance and extend the available product mix for automobile system designers. Meanwhile, to accelerate the product development and decrease time to market, ON Semiconductor has launched the NVG800A75L4DSC-EVK and NVH820S75L4SPB-EVK evaluation kits that to jump-start customer’s ability to quickly evaluate and develop electric vehicles and strengthening product competitiveness.

Being one of the largest suppliers of complete automobile semiconductors, IGBTs, and automobile MOSFETs, ON Semiconductor launched its PIM solutions to acceleration the adoption of electrified traction vehicle. VE-Trac  is the obvious choice for automotive traction inverter solutions with the best product performance, proven automotive quality, capable supply chain, and outstanding customer support.


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ON Semiconductor NCP398FCCT1G Specialized Power ICs and Modules

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