Leakage current sensor for EV charging stations

31st March 2021

LEM

Alex Lynn

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LEM has launched the CDSR, a new leakage current sensor based on its open-loop Fluxgate Technology. The CDSR is innovative, extremely compact and safe, allowing manufacturers to optimize the electronic design of their charger products.

With a worldwide total of only 7.3 million EV charging points, of which 6.5 million were private in 2019, the lack of an extensive charging infrastructure is a key impediment to the growth of the global electric vehicle market. To support the massive deployment of EVs, driven by ambitious policies to phase out sales of internal combustion engine (ICE) vehicles, the charging infrastructure must increase by thirteen times.

Due to this high expected demand, manufacturers of electric chargers must develop solutions that are competitive, affordable and capable of being industrialized at high volume. As well as being easy to install for the end user, they must meet many standard criteria, both for safety and robustness of the product.

Since 2016, 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 3.7kW to 22kW.

Following the trend towards digital electronics, the CDSR provides not only an analog 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.