LEM introduces the first automotive grade residual current monitoring Type B sensor for bidirectional OBCs

     To facilitate the transition of system engineers in the electric vehicle (EV) industry to transformer-less on-board chargers (OBCs), LEM developed the first automotive-grade residual current monitoring (RCM) type B sensor for bi-directional OBCs with ASIL B capabilities.

     In recent years, the utilization of bi-directional OBCs has markedly increased, enabling end-users to utilize their vehicle’s battery pack to power another vehicle, an electrical device, or even their residence. Nonetheless, due to their bi-directional nature, the OBCs pose certain safety problems. Designers must account for high voltage safety, particularly leakage monitoring and compensation, while simultaneously aiming to reduce weight, enhance efficiency, and minimize costs in bi-directional OBCs. The solution is a type B RCM automobile sensor, designated as CDT, that adheres to all applicable safety regulations.

     LEM’s latest sensor eliminates the concerns associated with designing-in solutions within constrained automotive environments and expedites the design architecture by being ISO26262 Automotive Safety Integrity Level B (ASIL B) prepared. More significantly, the new RCM type B sensor is paving the way in this rapidly evolving sector by allowing designers to respond promptly to the new ISO5474 Part 2 standard for AC power transfer. The standard emphasizes the functional and safety requirements for power transfer between the vehicle and an external electric circuit using AC, with a particular emphasis on electrically propelled road vehicles. The new standard, which covers conductive charging requirements for modes 2 and 3 according to IEC 61851-1, reverse power transfer through on-board standard socket-outlets or EV sockets, and voltages up to 1000V AC, is part of a series that operates in conjunction with ISO5474 Part 1.

     The new sensor is optimally adapted for use with bi-directional OBCs that enable vehicle-to-everything (V2X) applications due to its ability to address a variety of EV system engineers’ challenges in a single unit. This comprises vehicle-to-load (V2L), which is responsible for powering external devices, vehicle-to-grid (V2G), which is responsible for supplying energy to the infrastructure, and vehicle-to-vehicle (V2V), which facilitates communication between vehicles.

     The new CDT is capable of detecting current differences between two locations, which allows for the rapid isolation of faulty sections to prevent damage and the identification of faults such as short circuits. The new CDT sensor from LEM has been engineered to be the ideal complement for RCM type B in bi-directional OBCs. This sensor is capable of detecting and monitoring residual currents, including AC and DC leakage currents.

     This RCM variant is optimal for intricate electrical systems, particularly in electric vehicles with direct current components, and can identify potentially dangerous leakage currents. A bi-directional OBC may impair the detection and tripping functions of a Type A RCD if the DC fault current exceeds 6mA, hence elevating the risk of electric shock.