Leakage current sensor for EV charging stations

LEM has launched the CDSR, a new leakage current sensor based on its open-loop Fluxgate Technology.

The CDSR has been designed to be extremely compact and safe, allowing manufacturers to optimise the electronic design of their charger products.

IEC standards and more specifically IEC 62955 / IEC 62752, require the detection of a Direct Leakage current at 6 mA DC to avoid the home Residual Current Device (RCD) Type A being ineffective. This effect, called “the blinding effect”, appears when an EV develops an insulation fault.

EV architecture integrates a battery pack, powered by Direct Current (DC), which can generate a leakage current that can deactivate a home RCD. To protect the RCD and avoid the need to install an RCD type B in the electrical panel of home EV owners, EV chargers include a device to detect the DC leakage current. This detection is the role of the CDSR.

The CDSR has been developed to meet market demand for a residential and commercial charging station, offering a version for single-phase architecture and another for three-phase topology. With a maximum current per phase of 32A rms, the CDSR can be integrated into AC chargers from 3.7 kW to 22kW.

The CDSR provides not only an analogue communication output but also a Serial Peripheral Interface (SPI), enabling simple interfacing of hardware. The CDSR operates from a +3.3VDC supply and has a typical current consumption of just 50 mA when measuring 150 mA as a maximum primary residual current.

The ratio-metric behaviour of the CDSR ensures it can resist power supply drift and maintain a stable output measurement.

Robust, the CDSR can operate inside all EV chargers. It has an operating temperature between -40°C to 85°C, can withstand acceleration forces up to 10G while maintaining nominal performance, and has a very high level of insulation between its primary and measurement circuits, thanks to long creepage and clearance distances (13.2 mm).

Designed to ensure a high level of safety, the CDSR provides a default detection output signal with a reaction time below 200µs. Combined with an independent test winding, charger manufacturers can test the performance of the sensor in real time to guarantee maximum safety.