LEM launches the first automotive-grade residual current monitoring type B sensor for bidirectional OBC

To facilitate the transition of system engineers in the electric vehicle (EV) industry to transformerless on-board chargers (OBCs), electrical measurement technology expert LEM has launched the first automotive-grade residual current monitoring (RCM) Type B sensor for bidirectional OBCs with ASIL B functionality.

Image source: LEM

The use of bidirectional OBCs has increased significantly in recent years, allowing end users to use the vehicle's battery pack to power another vehicle, electrical equipment, or even a residence. However, due to its bidirectional nature, OBCs present certain safety issues. Designers must consider high-voltage safety, especially leakage monitoring and compensation, while also working to reduce the weight, efficiency, and cost of bidirectional OBCs. The new solution is the Type B RCM Automotive Sensor (also known as CDT), which complies with all applicable safety regulations.

LEM’s latest sensors eliminate the concerns of designing solutions in constrained automotive environments and accelerate design architectures by being ready for ISO26262 Automotive Safety Integrity Level B (ASIL B). More importantly, the new RCM Type B sensors pave the way for this rapidly evolving field, enabling designers to quickly respond to the new ISO5474 Part 2 standard for AC power transfer. The standard highlights the functional and safety requirements for power transfer between a vehicle and external circuits using AC power, with a particular emphasis on electric road vehicles. As part of a family of standards that operate in conjunction with ISO5474 Part 1, the new standard covers the requirements for conductive charging in Modes 2 and 3 as specified in IEC 61851-1, reverse power transfer through an on-board standard socket or electric vehicle plug, and AC voltages up to 1000V.

Because the new sensor can address a variety of challenges facing electric vehicle system engineers in a single device, it is ideally suited for use with a bidirectional onboard charger to enable vehicle-to-everything (V2X) applications, including vehicle-to-load (V2L) for powering external devices, vehicle-to-grid (V2G) for powering infrastructure, and vehicle-to-vehicle (V2V) for facilitating communication between vehicles.

The new CDT is able to detect the current difference between two locations, quickly isolating the faulty section to prevent damage and identifying faults such as short circuits. LEM's new CDT sensor has been carefully designed to be an ideal complement to the RCM B type in bidirectional OBCs. The sensor is able to detect and monitor residual currents, including AC and DC leakage currents.

This RCM version is best suited for complex electrical systems, especially electric vehicles with DC components, and can identify potentially dangerous leakage currents. If the DC fault current exceeds 6mA, the bidirectional OBC may impair the detection and tripping functions of the Type A RCD, increasing the risk of electric shock.