Transformation of development facilities and testing requirements for electric powertrains

e-motec
March 31, 2022

Transformation of development facilities and testing requirements resulting from electrification of powertrains

Simon Zettler, Benedikt Grob

The electrification of powertrains and the increase of electric vehicles poses a great opportunity for clean mobility replacing more and more of the conventional cars and buses on our roads. Being seen as a great chance for a greener future on one hand the transformation to electric mobility comes with a couple of challenges as well.

Some are obvious and have an immediate influence on society such as the demand for new infrastructure in the form of charging possibilities or a higher demand in electrical power resulting from additional electric cars on the roads. Some reach back to the development and homologation of new technologies on OEM or supplier end.

Many traditional car manufacturers have planned their testing fields solely for testing and developing fuel powered drives, measuring vehicle emission or optimizing every single component involved in complex combustion engines. However, the development of BEVs (Battery Electric Vehicles) comes with the need of large amounts of electrical power which oftentimes was not considered when planning the infrastructure for test fields several years ago.

Taking for example endurance test bench centres. Large amounts of chassis dynos are operated in parallel testing cars for endurance, range, long range quality, etc. In a conventional car the use case is easy, it is driven until empty, refuelled within minutes with the driving continuing afterwards. With electric cars, refuelling is not as easy. Plugging it into a 230V plug means several hours of idle times on a test bench not using the capacities the test bench offers nor the possibilities the BEV allows for in charging. Creating new infrastructure only for charging and electrical power means large building investments. However, there are large amounts of electrical power inside those test centres used to operate the test benches themselves (actually in all chassis dynos) which can potentially be used to repower empty batteries. The dyno itself recovers energy the car generates while driving transforming it from mechanical power into electrical power which is then led into the public supply network. This energy as well as the infrastructure can be used to generate the DC Power needed to quick charge electric cars with potentially several hundred kW, the battery being the limiting factor in this scenario. Using the existing DC link allows for optimal usage of car generated energy with minimum load on the grid as well as the least possible amount for structural investments. Keeping the energy in the loop between the test bench and the charger allows for an efficient way of repowering empty batteries without external input.

diagram showing chassis dynos on EVs

A similar use case can be applied for motor and powertrain test benches. In a world where most cars worked on combustion engines the test bench only had to feed back energy created in the cycle through the frequency converter into the AC grid. Modern test benches for electrical power trains however are mostly in need of a highly powered DC source, mostly in the form of a battery simulator, powering the DUT from the AC grid while the frequency drive of the load machine recovers back into the grid. With limited electrical supply and a lot of power needed to work with, a more efficient setup would be to create a DC grid for the test bench with bidirectional participants (e.g. motor inverters, battery simulator) and keep the energy cycling through the test bench instead of feeding back into the AC grid as the picture below shows. This way a large amount of electrical power can be used testing with minimal requirements for the infrastructure. The power input here only has to cover for the efficiency losses in the system. A setup like this is applicable for all kinds of powertrain tests, be it climate, NVH, EMC or just regular setups for motors, axles or any other test setup with high energy requirements.

diagram showing potential DC setup for EV test benches

Apart from transformational challenges regarding existing test benches and infrastructure also the kinds of tests themselves will undergo changing requirements. Where the focus in the past lay on emission testing for exhaust gases, EVs will produce other types of emissions, e.g. electro magnetic emissions. The examination of cars in respect of electro magnetic emissions and immunity against such influences has been known to car makers as for homologation such tests had to be made for the complete car. With more and more electric powertrains in BEV there are potentially more sources (e.g. fast switching IGBTs of the converters) for electromagnetic emission as well as potential failures in terms of external influences.

So far most car makers have focused on testing the complete car for conformity to the regulations valid in those countries they want to sell into. The increase in electric cars has caused new regulations to come up concerning different parts and functions of the vehicle. For example, a BEV must pass an EMC test procedure during the charging and discharging process, whereas certain limits in terms of immunity and emission have to be kept to. For most EMC Dyno operators this means additional testing they have to comply to inside their existing test chambers or building new chambers for special purposes. Also in this use case it might be worth looking into the possibility of using the existing infrastructure and incorporate different functions such as charging into an already equipped laboratory.

image of EV undergoing tests

Containing loads of electrical components, controllers, switches and many more, performing a final examination on the complete car only on final acceptance may be too late in a developmental area. Whereas there are by law or regulation no tests are required for components, EV developers have determined an advantage in performing early stage EMC tests for certain components such as the battery, the OBC or the powertrain, giving them a first hint of the performance that can be expected when used inside the BEV. Developmental facilities of this kind are at the moment quite rare due to their special requirements but will certainly be seen more often in modern BEV test facilities. Again, converting an emission test bench for a combustion engine into an EMC test laboratory conforming to existing regulations such as CISPR25 requires not only a certain amount of electrical power as mentioned before in this article but also a lot of space in order to account for the EMC measurement equipment and the hall size that is defined by the norm.

All in all, conventional test facilities that have been operated for decades must now be under review in order to maintain a competitive development environment for future mobility. The clever usage of energy, infrastructure and space is key for redesigning existing R&D centers for the challenges of E-mobility. Be it either energy efficient setups for charging and testing, adding new possibilities to existing benches or the design and incorporation of entirely testing possibilities, electrification also means challenges and chances for the redesign of existing development areas.

Simon Zettler – Sales Manager E-Mobility, AIP Automotive

Benedikt Grob – Head of Development at AIP Automotive

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