60 power electronics. This switching matrix enables the targeted allocation of power units to several charging points as required, as well as the operation of individual modules in optimum power ranges. A central controller controls the energy flows from a grid connection or a second life stationary storage system, thus reducing the peak load on the power grid. At the same time, a dense and powerful public charging network is required for long-distance transport applications. In distribution transport, on the other hand, megawatt charging is often not required because intelligent fleet and charging management can significantly reduce energy and grid costs at the depot. These high currents need highperformance protection from a contactor that can quickly and reliably isolate the truck from the high currents and voltages. “Looking at the developments in early 2024, we decided that it makes sense for us to go in this direction, to develop a contactor to support this trend to MCSs, and we are experts in switching high voltages and high current, so this is the logical next step,” says Guenther Rott, who is responsible for global product management and application engineering at Schaltbau, which was involved in the NEFTON project with MAN. “It is interesting for us and we are in concrete projects with German truck makers,” he says. “We also work on both sides, both the truck or eBus and on the charging side.” The company worked with MAN to develop optimised 1000 A charging with a 3000 A concept for the 10 prototype trucks developed last year with the first live MCS and new cooling concepts. The most challenging point is on the infrastructure side because an intelligent system is needed for charging 10 or 20 trucks at the same time on the highway. This started off with the C800 contactor that was developed for high volume e-mobility designs. The C800 series is used in the truck’s power distribution unit (PDU) for battery emergency cases, in which the contactor safely disconnects the current to safeguard the vehicle, driver and freight. The bidirectional contactor is notable for its high current carrying capacity and its high energy efficiency, making it perfectly suited to switch power in a small space and in applications with energy recovery, such as the PDU of modern e-vehicles. “We used two C800 contactors initially up to 1 kA in parallel, but this is not the final target. Phase two of the development is the C320 that under specific conditions can handle up to 2 kA depending on the busbars that are used and what cooling is installed,” Rott says. “We have prepared some samples and they are in testing with a truck manufacturer.” “What we are working on is a product that can cover up to 3000 A, the C330. The key point is always the thermal balance. This is an issue of the physics because the hotspot is always near the contact, so the trick is to have really low contact resistance to reduce the power loss as much as possible in this critical area, and there we have a special concept,” he continues. “This integrates two functional groups,” says Rott. “One functional group will do the hot switching and the load, while a separate group is responsible for keeping the contact resistance over the lifetime of the product at a suitable low level. It’s a combination of all our experience of the last 50 years of r&d in high-current contacts. This comes from the design of the inner bus bars and the question of the contact materials used, and the power of the coil system and selfcleaning of the contact system.” There are two different versions for trucks and stationary chargers. “The current you need in the truck you need in the charger, so the products are corresponding but not the same type,” he says. May/June 2025 | E-Mobility Engineering Positioning of CCS connectors for charging (Image courtesy of NEFTON) The contactor in the MCS inlet in the NEFTON project (Image courtesy of Schaltbau)
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