April 12, 2021

Power boost with 800V systems – development of high voltage technologies for new generation e-models

hofer powertrain constantly strives to update and develop better charging technologies, that promise to reduce the waiting times at the charging station drastically, but more importantly, to make range anxiety a matter of the past.
Power boost with 800V systems – development of high voltage technologies for new generation e-models

We are witnessing the disruption of the automotive market by renewable energies, decreasing costs for e-batteries, alternative energy sources are becoming more appealing, and powerful storage solutions are in demand. In this part of our Electrification Weeks, we address future-oriented technologies, looking at 800V inverters and some neighboring technologies, their advantages, and their potentials in developing and implementing new-generation vehicles.

Growing demand for more electric vehicle efficiency, higher charging convenience with appropriate infrastructure, and reduced charging times leads many car manufacturers to explore and develop new age charging systems and technologies such as 800V inverters enabling higher efficiency and cost-effectiveness.

This technology promises car manufacturers to gain more power into their new vehicle fleets quicker and recharge at speeds that match the fast-moving market with the soon improved infrastructures, capable of handling 800V. This charging technology promises to reduce the waiting times at the charging station drastically, but more importantly, to make range anxiety a matter of the past. In recent years, car manufacturers have often been confronted by consumers' skepticism towards electric cars, wishing better solutions in charging technologies. New technologies are entering the market and help change this mindset. As the infrastructure evolves, fast charging solutions such as 800V technology are gaining in speed, respectively – 800V-capable DC rapid charging infrastructure is a key enabler to extreme / ultra-fast charging XFC technology. hofer powertrain has been developing its 800V systems to help its customers achieve extended range, as a new norm, with the convenient EV systems. Our teams provide development services and technical support for individual needs through testing, simulation, technical, and concept studies to implement specific vehicle concepts.

There are two main advantages in using 800V systems, improving inverter’s efficiency: faster charging as more power is transferred in less time and reduced power losses in the cabling. Meanwhile, improved performance (i.e., power) for electric powertrains can be achieved through either higher current or higher voltage. Compared to a 400V system, less current is required for an 800V inverter to transfer the same power. When running at a lower current with higher voltage, there is less loss as heat, and therefore smaller, lighter cables and connectors are required.

Key considerations when moving from lower voltage to 800V systems:  

  • Careful component selection – hofer powertrain support customers throughout the entire development and implementation process in dealing with suppliers and brings the essential knowledge of the market needed to select the right set of components to assemble a system in alignment with customers’ needs.
  • Increase in the HV creepage and clearance requirements – battery-engineers define insulative properties between voltages and determine distances needed between the components within the whole inverter design, allowing separation between parts on the PCB and the PCB tracks themselves.  
  • With a growing number of commoditized components available, the right selection of high voltage automotive-qualified components may help avoid higher development costs. A tremendous amount of understanding of different components, their availability, benefits, and downsides is crucial.  
  • From a technical point of view, the DC link capacitor is a significant part of the inverter (packaging, EMC/current ripple) and an important cost driver that should be considered during the inverter component selection activity.

Use of silicon carbide semiconductors (SiC) technology for overall higher efficiency, power density, and cooling requirements.

With new infrastructures becoming more and more available, updating switching technologies is important to keep up to date. In this light, moving from insulated-gate bipolar transistors (IGBT) to a SiC switching technology carries the advantage in the switching speed and quick change of higher current. This influence on the crossover of current and voltage, making it shorter, leads to less power loss in the module. Consequently, compared to the IGBTs, still often used in traction inverters, SiC technology meets higher operational requirements of the new vehicle models, allowing them to operate at much higher voltages since IGBT faces challenges when switching at high frequencies.  

 

Nevertheless, both switching technologies have their respective potentials and can run in either 400V or 800V systems. Here at hofer powertrain experts run early simulations to aid the selection of the most efficient switching technology for the specific use case, considering all essential parameters.

Energy efficient control of dynamic, precise and secure traction torque

Compact PE215-800V ONEboard solution developed by hofer powertrain
Compact PE215-800V ONEboard solution developed by hofer powertrain

Our compact PE215-800V ONEboard solution with highly customizable functions delivers state-of-the-art power density for hybrid and fully electric applications with up to 99.3% efficiency. This module's main aim is to provide the highest power density in the smallest package while maintaining high standards for performance in controlling the power electronics.

Some highlights of our 800V inverter with the in-house developed ONEboard system:

  • Time & cost-efficient
  • High performance with the latest silicon carbide technology
  • Water-cooled power module & DC-link capacitor
  • Maximum package efficiency, easy to adapt and integrate in any architecture
  • This system is a single microprocessor solution, which uses 50% less hardware compared to similar solutions

As a supplier of all components of electric drive units, including power electronics, transmission, software and electric machine (EM), the design of these components is within hofer powertrain´s full control. This allows close-up analysis, i.e., the impact of increasing DC link voltage on the EM performance and precise follow-up modifications.

The impact on the Inverter is usually significantly greater than the impact on the e-machine since the e-machine is designed for every voltage of receiving. However, in some cases, upgrades to the e-machine can lead to improved dealing with higher voltages as well.

The experts at hofer can calculate and analyze the effect of increasing the machine's maximum operating speed, so careful consideration can be given to the system design approach (e.g., transmission ratio impact, bearing selection, mechanical integrity of the rotor, among others). Since the main powertrain power electronics component influenced by the voltage selection is the inverter (DC to AC), simulations to study the efficiency impact on the inverter power modules can be performed.  

 

As mentioned above, increasing voltage has less package or weight impact in comparison to higher currents. However, it leads to increased creepage and clearance distances which need to be considered in high-voltage component design and packaging. The teams are specialized in finding the right solutions by modeling the systems early in the development process. They can calculate an ideal solution and its exact characteristics for it to run according to the requirements.

A global race has been sparked to electrify our roads, moving at high speed from combustion vehicles to hybrids of all kinds to efficient, fully electric cars. OEMs and engineering teams are focusing on further developments and improvements to accomplish this mission, where particularly one component is very apparent – the energy storage solution. In our next part of electrification weeks, we will address OEMs' current challenges in building better e-batteries with higher capabilities, matching the ever-improving infrastructure, and highlighting significant technological progress. Besides, we touch upon new interesting energy sources such as fuel cell, which already has joined the race, explaining the areas these technologies will benefit the most and the deliverables hofer powertrain is preparing for the challenges.

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