Advanced Residual Current Monitors for EV Charging: Analog and Digital Outputs

Lem, a leading provider of electrical measurement solutions, has recently unveiled a pair of mains residual current monitors specifically designed for electric vehicle charging. These innovative monitors offer both digital and analogue outputs, providing users with accurate and reliable measurements.

Monitoring High-Power Energy Sources

Electric vehicles are known for their high voltage batteries, which also make them a high-power energy source. To ensure the safety of users and prevent any damage to household switchboard protection, careful monitoring of these vehicles is essential. Lem recognizes this need and has developed a method to monitor AC and DC current leakages, with the ability to measure leakage as low as 5mA.

Digital and Analogue Outputs

Each of the monitors features both digital and analogue outputs. The digital output utilizes the SPI bus, while the analogue output is a 48MHz differential ΣΔ bit stream. To create a 0-3V signal, a pair of external RCRC filters and a high-impedance load are required. These monitors are suitable for PCB mounting and come with sensed current conductors built into the devices.

Wide Range of Applications

The monitors can handle up to 32A (3.3kA peak), making them suitable for AC charging systems ranging from 3.3 to 22kW. Both IC-CPD ('mode 2', in-cable control and protection device) and wall boxes (mode 3) can be used with these monitors. The three-phase version has a compact footprint of 56 x 51mm and stands 26mm above the PCB.

Precision and Accuracy

With a trip output set at 70mArms of residual current, the monitors comply with IEC 62752/62955/UL 2231 tripping standards. The measuring range is ±150mA, and primary-to-secondary creepage and clearance are carefully maintained at 10.15mm in the three-phase version and 13.2mm in the single-phase version. Inside, fluxgate sensing is utilized, requiring a separate 3.3V (50mA max) supply.

Errors in the measurements are minimal, with a maximum of 0.5mA up to 6mA residual primary current, followed by 1mA error up to 10mA residual. Above 10mA, the error is 10% of the measured value. It is important to note that these values are dependent on power supply accuracy. The digital output offers a higher bandwidth mode (2kHz) but sacrifices some accuracy.

Reliable Operation and Guarantee

The monitors are designed to operate in a wide temperature range, from -40 to +85°C, ensuring their reliability in various environments. Additionally, Lem provides a five-year guarantee for these monitors, giving users peace of mind.

Conclusion

Lem's new mains residual current monitors for electric vehicle charging offer a comprehensive solution for monitoring high-power energy sources. With their digital and analogue outputs, wide range of applications, and precision measurements, these monitors are a valuable addition to the electric vehicle charging infrastructure. Their reliability and guarantee further enhance their appeal to users seeking accurate and safe monitoring solutions.

Resources:

• Three phase residual current sensor data sheet
• Single phase residual current sensor data sheet