Specific inverter topology for800V developed and tested in-house is presented in our 3-L-inverter, with benefits on a system level. While searching for powertrain solutions with the best system performance, we compared different switching topologies (IGBT, SiC and GaN) according to KPIs such as WLTP impact, side-effects, and costs, based on various technology combinations. The results show that our new 3-level GaN high-voltage solution leads the way. This solution promises an optimal trade-off of performance and optimized costs. With the 3-level switching pattern, hofer powertrain significantly boosted the overall performance. The NVH behavior and EMC are drastically improved compared to 2-level inverters. The difference between the 2 and 3-level inverters lies in the number of electric potentials to control the voltage waveform of the converter output. A 2-level inverter has 3 voltage levels (0, + and -) to the output and a 3-level inverter allows two more voltage steps (+/2, -/2) in between leading to a better current output and an improved control quality. The advantages concern mainly the primary drives in EVs, where energy consumption is most relevant. Yes, the switching behavior of GaN technology stands out compared to IGBT and SiC solutions, but it bears one downside. For future relevant applications, it cannot operate at higher voltages due to the lower break down voltage and the only way to use the full potential of GaN technology for 800V applications is to integrate it into a 3-level inverter. This allows us to make the technology future-proof for our customers and their powertrain applications, where performance is comparable to the SiC technology, but at reduced costs of the chips up to factor 2. This brings major additional opportunities since power chips represent the main cost drivers in inverters.
Existing charging infrastructure and stations installed around the globe cater only up to 400V DC charging capabilities. The 800V vehicles are gaining momentum and compatibility to the currently available 400V charging infrastructure is a growing necessity in order to bring high-voltage cars into mass adaption. To achieve this compatibility and simultaneously avoid costly installations (especially in mass production) of the known today additional DC / DC converters which boost 400V to 800V, our hofer powertrain booster technology and an in-house developed architecture allow such compatibility and rapid charging using a combination of inverter and motor, involving minimal effort, and providing maximum cost efficiency. During charging the power stage of the inverter is used in combination with the inductances of the motor to allow step up converter functions. The mentioned cost reduction is reached since the technology is integrated into already existing EDU platforms where the subcomponents can be mixed and matched according to customers’ requirements and power is a scalable commodity. The high-voltage booster functionality proved high stability and operability in combination with a variety of e-motor types.
New heights in efficiency and a significant increase of power density for a wide range of motor types are reached with the new hofer powertrain Litz wire technology. The potentials and benefits of today’s state-of-the-art hairpin winding, and the commonly used pull-in winding system have been combined in a new litz wire winding. Here, the smaller wires from the pull-in winding have been compressed to achieve the same filling factor and copper density as the hairpins and at the same time allow outstanding high-frequency behavior of the standard pull-in wiring, therefore pushing the boundaries for high-speed EDUs.
· UP TO 25% LESS POWER LOSS IN THE E-MOTOR
· E-MOTOR MASS REDUCTION UP TO 25%
· MAXIMIZED CURRENT DENSITY
Moreover, the thermal conductivity is further optimized compared to the pull-in winding. The technology evolved in close collaboration with our industrialization teams based on an agile development and testing approach with high level of analysis, testing and close monitoring helped accomplish the most crucial stages. hofer powertrain specialists brought this technology to a mass volume industrialization level, ready to be delivered to our customers even on the global scale.
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