What Are AC Charging Stations?
AC chargers (Alternating Current chargers) are used to charge electric vehicles (EVs) by converting AC power from home or office supplies into DC power for the vehicle’s battery. They are ideal for overnight or workplace charging but take longer than DC chargers. Current sensors in AC chargers measure output current and detect leakages to ensure safety and efficiency.
AC chargers take AC electricity from the home or office power supply and feed it into the vehicle’s onboard charger, which then converts this AC power into Direct Current (DC) to charge the battery of the EV. The main advantage of AC charging stations is that they can be installed in homes or workplaces, allowing EV owners to charge their vehicles overnight or during work hours.
Why Are Leakage Current Sensors Important in AC Chargers?
In AC chargers, the incorporation of DC leakage current sensors (also known as Residual Current Sensors) is crucial for ensuring the safety and efficiency of the charging process. DC leakage current refers to the unintentional flow of direct current to the ground, which can pose serious risks if not properly monitored.
Addressing the “Blinding Effect” of RCD Type A
The “blinding effect” of Residual Current Devices (RCD) Type A can be a significant concern in AC charging stations, particularly when these devices are subjected to high-frequency DC leakage currents. The blinding effect occurs when RCD Type A incorrectly interprets DC leakage as normal AC current, rendering it less effective in detecting actual faults.
Leveraging RCD Type B for Enhanced Safety
Opting for Residual Current Devices Type B provides a viable solution. RCD Type B is designed to accurately detect both AC and DC residual currents, eliminating the blinding effect associated with RCD Type A. This ensures that the RCD remains effective in safeguarding against electrical faults, offering enhanced protection for users and the electrical vehicle supply equipment.
LEM Sensors for AC Charger Safety and Reliability
LEM offers advanced solutions that seamlessly integrate into AC chargers, addressing critical safety issues. The inclusion of a CDSR DC leakage current sensor ensures that potential faults are promptly identified, enhancing the overall safety of the charging system.
CDSR Series — Leakage Current Monitoring
CDSR is a leakage current sensor developed to meet market demand for residential and commercial charging stations, offering versions for both single-phase and three-phase architectures. With a maximum current per phase of 32 Arms, the CDSR transducers can be integrated into AC chargers from 3.7 kW to 22 kW.
These sensors are RCD (Residual Current Detector) Type B, featuring 1 mA DC measurement, SPI and analog output communication, and can operate within a temperature range of -40°C to 85°C. Utilizing Fluxgate technology (open loop), CDSR current sensors provide reliable and accurate leakage current measurements for residential applications.
- Primary current: 32 A RMS
- Measuring range: ±150 mA AC and DC
- Accuracy: ±0.5 mA at 5 mA AC and DC
- Dual output: digital (SPI) and analog
- Test winding included
- Operating temperature: -40°C to 85°C
- Bandwidth: DC to 2 kHz
- Compliance: IEC 62752 / 62955 / 61851-1 / UL 2231-1,2
AC Chargers, Wallboxes & Charging Cable Current Sensors
AC charging stations require accurate components. LEM’s current sensors, renowned for their precision, ensure the exact measurement of output current. Current Sensor IC and the CKSR product family are the components of choice to measure the output current of AC chargers.
CKSR Series — Output Current Measurement
The CKSR family provides accurate output current measurement for AC chargers and wallboxes, enabling precise billing and safe charging operation. These sensors are designed for PCB mounting and offer galvanic isolation between the primary high-power circuit and the secondary electronic circuit.
With LEM’s expertise in current sensing and monitoring solutions, users can confidently deploy AC chargers with a robust safety framework. By combining leakage current sensors and accurate current measurement, LEM empowers AC charger manufacturers to meet and exceed safety standards, providing reliable and secure charging solutions for electric vehicles.
