Development of Adaptive Connectors Based on Shape Memory Alloys

A major limiting factor in the charging time of fast-charging electrical vehicles is the maximum electrical power that can be transmitted through the contact points between the charging plug and the vehicle inlet. The electrical contact resistance (ECR) thereby plays a decisive role. By increasing the contact surface between these contact points, it is possible to decrease the ECR, leading to higher transmission power and reduced charging times. Due to the limited construction space, high contact forces between the charging plug and the vehicle inlet are required to reduce the ECR. However, high contact forces complicate the insertion of the plug by hand. In consequence, lower contact forces and significant heating of the connection have to be accepted. For this reason, today’s systems (e.g., Combined Charging Systems (CCS)) include active cooling of the contacts.

This paper presents an alternate system that temporarily increases the contact force of connectors during charging with shape memory alloy (SMA) actuators. To ensure industrial applicability, the research is conducted on the example of a CCS Type 2 charging plug. Initially, the correlations between extraction force, contact normal force and resulting ECR are investigated experimentally. Subsequently, basic mechanisms for increasing the contact normal force with SMA wires are presented and experimentally validated. As a result, a reduction in ECR of up to 60% has been experimentally demonstrated.