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Material solutions help decrease safety risks of electrical powertrain systems

12 March 2020
  • Dr Tamim Peter SidikiGlobal Marketing Director Electronics at DSM Engineering Materials

As the automotive industry evolves—phasing out ICE vehicles and manufacturing more electric and hybrid vehicles—more and more knowledge is gained about electrical powertrains. Whether the e-motor will be powered by large battery modules or by a fuel cell in conjunction with a smaller battery, electrification requires new systems and components, such as high-voltage charging, lithium-ion battery technology, fuel cells, power e-motors, and AC-DC inverters or DC-DC converters.

It’s imperative the industry considers safety requirements of these components—if not, consumers would likely suffer major drawbacks in the safety of EVs. Because the electrical powertrain typically operates at high voltage with currents of several hundred amperes, safety has never been as important as it is today.

For example, with a transition to high-voltage electrification with unattended battery charging, the high-voltage system could pose a risk of short circuits or sparks, which could lead to a fire. Also, there have already been multiple reports of serious fires caused by the built-in lithium-ion batteries, even when the car is parked and not running.

What if someone charges their EV at home, in their garage (as shown in the middle image below)? The imminent risk of a dangerous fire burning down the garage and threatening the lives of residents becomes obvious. Based on this scenario, it’s easy to understand why we are going to see more requirements for higher flame retardancy (UL94-V0), Glow Wire Ignition Temperature (GWIT) or Comparative Tracking Index (CTI).

Expected future change of flame retardancy requirements in automotive

Flame retardant materials will be required in EVs

There is no doubt that flame retardant additives are not desirable in automotive plastic applications at this time because they lower the material performance, such as mechanic properties and flowability. They also add extra weight and cost, which every designer is challenged to decrease. However, we anticipate that in the near future there will be a strong move to require flame retardancy for all components in the high-voltage path—from the charging plug to the e-motor. This requirement may be triggered through OEMs or tiers. Also, this could be imposed through regulatory bodies or legislation.

Let’s look at flame retardancy in transportation—it is all about increasing the escape time in case of an emergency (as shown in the left image above). In an airplane with little opportunity to escape, even the seats and carpets need to pass the highest flame retardancy specifications. A car is different because the driver or passenger can escape easier than a passenger on a plane. Currently, passing the required flame tests is therefore easy for cars. At this time, there are only a few applications and manufacturers that require the use of UL94-V0 certified plastics in vehicle on-board electrical insulations.

A higher electrical power with minimized power losses

While mild hybrid cars have a 48V low power battery, today all fully hybrid cars and commercially available battery electrical vehicles run at voltages between 200V and 400V. To increase the power of the battery further, we currently see a strong move in the market from 400V to 800V batteries, including an ultrafast charging network that is currently rolled out in Europe, with the new Porsche Taycan being one of the first commercially launched cars to  utilize this high-voltage technology.

Industry players are actively working to move to even higher voltages in the range of 1.000V and above. To achieve an overall higher electrical power at minimized power losses, the increase of voltage is preferred as opposed to increasing the current. Electrical losses in conduction scale with the square of current (P~I²). This is conceptually shown in the below graph.

The benefit of pushing voltage to a higher level in the electrical powertrain

The transformation of the powertrain from ICE to e-drive also means a change in high-performance plastics used for electrical insulation and structural components. For ICE engines, plastics need to perform in parameters such as low wear and friction, continuous high operating temperatures up to 230°C or oil resistance. In electrical cars, key enablers are going to be parameters such as dielectric strength, CTI, thermal conductivity, flammability resistance or EMI shielding.

The below chart summarizes the impact of the applied high-voltage systems in electrical cars on key requirements for insulation plastics used in the high-voltage path.

Impact of electrification on engineering plastics used in automotive

Helping customers build up required competencies

DSM is covering a broad portfolio of engineering plastics from aliphatic polyamide (PA) 6, 46, 66, 666 and 410 to aromatic PA 4T (PPA) and extremely high-Tg (up to 160°C) PA 4T (ForTii Ace), as well as PPS, PBT, PET and thermoplastic copolyetherester (TPC). Among these plastics, PA6, PA66, PA 4T, PBT and PPS will meet the requirements of the electrical powertrain.

A key differentiator of DSM is the long-term experience in both the electronics and the automotive industry. This offers significant added value to Tier 1s and OEMs. The ongoing conversion of these two industries pushes traditional automotive players to quickly build up their IT and electronics knowledge, while IT companies establish experience in structural car design.

DSM is a key player—especially in this phase of conversion—helping its customers from both industries to build up the newly required competencies. Materials that have already been developed and approved can now be applied in new applications. Supported by additional CAE and simulation knowledge, this will help speed up the time to market and improve safety.

 

To meet these upcoming requirements, DSM has used its long-term expertise in electronics and developed a full portfolio of materials specifically targeting the high-voltage charging path in hybrid and fully electrical cars, as shown above.

To learn more about DSM’s advanced materials for hybrid and electric vehicles, contact us or visit plasticsfinder.com.

Download the article "Drivers of Electromobility" to read more about flame retardancy, heat and tracking resistance of EVs 

    

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