King County Metro receives 123 inverted pantographs from Schunk Transit Solutions for electric bus charging

Schunk Transit Solutions is installing 123 inverted pantographs at King County Metro’s Tukwila Base bus depot. The system enables electric bus batteries to recharge within minutes. Full commissioning of the new charging infrastructure equipped with Schunk pantographs is scheduled for spring 2026.  

King County Metro operates approximately 1,200 buses in Seattle, 1,100 hybrid (battery-diesel) buses and more than 300 fully electric vehicles. The agency notes that during a pilot phase involving six SLS 201 pantographs, Schunk Smart Charging demonstrated its performance under real-world conditions.  

“There were no power interruptions caused by vehicle movement or high humidity. The high reliability of our pantographs convinced King County Metro,” said Schunk Transit Solutions Head of SBA Battery-driven Vehicles Timo Staubach. 

In addition to roof-mounted charging systems installed on the buses that communicate with the charging station, Schunk Transit Solutions also offers inverted systems like those used in Seattle. The SLS 201 series pantographs are integrated into the charging infrastructure, whether in depots or at stops along the route.  

The system connects to buses via High Power Charge Rails (HPC rails)—charging rails mounted on the buses’ roofs. The pantograph lowers using a top-down mechanism and transfers electricity from the charging infrastructure via the HPC rails to the bus battery. The battery can be recharged during brief stops along the route, a process referred to as opportunity charging. In combination with the spring-and-drive system built into the SLS 201 pantograph, four separate charging rails on the vehicle roof ensure maximum flexibility in making contact.  

“The pantograph automatically compensates for vehicle movements during the charging process. This ensures that every contact point maintains a reliable connection,” Staubach said. “The distribution of the rails also helps prevent insulation faults during the charging process caused by high humidity or rain.”  

Charging is performed using direct current, enabling rapid transmission with almost no energy loss. In addition, the pantograph’s mechanical contact sequence enhances system safety while minimizing wear on both the pantograph and the HPC rails.  

The SLS 201 pantograph evenly distributes a contact force of up to 110 newton-meters across all four contact points, even in extreme parking positions. This is made possible by the system’s wide operating range. Via its spring-based connection, the pantograph can reach up to 1,600 millimeters (63 inches).  

“This versatility is important for operators whose fleets consist of different vehicles with varying heights, as is the case in Seattle,” Staubach said. “Our pantograph can accommodate these differences.”  

Schunk Transit Systems meets “Buy America” requirements. The pantographs are manufactured at the company’s U.S. facility in Wisconsin and are labeled and certified in accordance with U.S. safety standards. 

In addition to supplying the pantographs, Schunk’s contract with King County Metro includes support for their commissioning, maintenance and technical training. Schunk’s pantographs are already in use in major North American cities, including New York, Boston, Washington, Miami, Chicago, Toronto and Vancouver.