By Dermot Byrne, Industry Marketing Director, Transportation, TTI
As the European Union implements its Green Deal goal to be carbon neutral by 2050, governments and environmental groups are demanding cleaner cities and a reduction in greenhouse gases and other pollutants. To stimulate demand, European countries are increasing subsidies to vehicle owners to encourage them to invest in electric vehicles as a reliable and alternative clean method of transportation. This change is in turn driving manufacturers of vehicles as diverse as e-bikes, cars, vans, buses, agriculture and construction equipment to rethink their design and to use electric and hybrid transmissions to increase the efficiency of their vehicle powertrain whilst eliminating exhaust gases and pollutants.
For the engineers developing these next-generation systems, selecting the right high-voltage connection system can be a daunting task. Should they use shielded or unshielded connection systems, plastic or metal connectors, flat blade or circular contacts, PCB or busbar-mounted connection systems? How will they meet their sealing performance, vibration and latching requirements? How can they reduce cost in their systems, and are there second-source suppliers available? These challenges are becoming increasingly difficult as manufacturers introduce second- and third-generation versions of their high-voltage connection systems.
In automotive applications, where production volumes are usually high, engineers are trying to find a balance between performance, reliability and cost. Connection systems are usually manufactured in plastic housings and feature HVIL contacts, TPA and CPA components as standard. Most connectors support voltage levels up to 800V, with many German OEMs insisting that these connectors are designed and tested according to LV214 and LV215 standards whilst other OEMs require validation acc. USCAR or an OEM-Specific standard. Many connectors feature flat blade contact systems that both increase the current-carrying capability and enable reliable crimp termination whilst maintaining a competitive cost level. Examples include TE Connectivity’s PCON12 terminal system, which is used in the new HVA1200 AK Class 2/3 product family that supports currents up to 100A for auxiliary device applications.
Cost is another critical topic and some OEMs are demanding second sources for their connection systems. Suppliers like Aptiv are therefore now offering products that are 100% intermateable with other AK Class 1, AK Class 2, AK Class 4 and AK plastic Pass-Through connection systems, whilst simultaneously improving the connector sealing and vibration performance, with respect to the existing designs. Aptiv has also developed its new HV RCS 800/890 Direct Mate connection system, where the cable plug connects directly to metal device housing, again removing cost from the overall interface.
An associated trend is that vehicle manufacturers are reverting back to using lower-cost unshielded cables and connection systems in combination with EMI filters to again remove cost and weight from their systems. In line with this trend, other OEMs are evaluating moving from copper HV cable to an aluminium option in the mid-range amperage and voltage ranges. There is still a long way to go before proliferation, and there are a lot of considerations to be aware of, including increased diameter size, cable flexibility and product availability, amongst others.
In heavy equipment and commercial vehicle applications, designers are focusing on the challenges of meeting the higher power requirements of these vehicles. Whereas truck and bus OEMs still tend to prefer plastic connection systems, agriculture and construction vehicle OEMs often prefer to use metal connector systems for increased ruggedness and reliability. Voltage specifications of up to 1000V are considered standard and current levels above 500A are becoming more common. This requires customers to use thicker 70 mm2, 95mm2 or 120mm2 cables, which can be both heavy and relatively expensive. Finding a reliable contact system that allows users to limit cable sizes can help optimise design cost.
A final design consideration for engineers is their high-voltage cable assembly strategy. High-voltage cables are challenging to assemble, and the required crimping and testing equipment can be expensive, so not all traditional harness makers will be able to produce these cables. Particularly for small-volume OEMs, engineers will need to consider up front if will they build cables in-house, source via a local cable harness maker or distributor, or if their volumes will be sufficient to be supplied directly by a connector manufacturer. Finding the right local partner or distributor during the development phase can make sourcing a lot simpler when their vehicle is ready to go into full production.