How Electric Vehicle Supply Equipment (EVSE) Works
Understanding how Electric Vehicle Supply Equipment (EVSE) functions is crucial for anyone interested in electric car charger testers. EVSEs are designed to connect power to electric vehicles (EVs) to charge their batteries, with various modes offering specific functionalities.
EVSE Modes and their functions
Mode 4 EVSEs convert power from AC to DC before supplying it to the EV, ensuring safe and efficient operation through special control and protection functions. Modes 2, 3, and 4 communicate with the EV using two signal lines: the Proximity Pilot (PP) and the Control Pilot (CP).
Proximity Pilot (PP)
The primary function of the PP line is to confirm the presence and proper connection of the vehicle, preventing it from driving away during charging. According to the EN 62196 standard, the PP line also indicates the maximum charge rate supported by the charging cable, particularly relevant for non-tethered cables.
Control Pilot (CP)
The CP line is the main communication route between the EVSE and the EV, managing the charging process with six defined states: no vehicle connected (A), vehicle connected but not ready to charge (B), vehicle connected and ready to charge without ventilation (C), vehicle connected and ready to charge with ventilation (D), no power (E), and error (F). Some EVs require ventilation to limit battery temperature rise during charging, provided by vehicle fans. The CP line also uses a pulse-width modulated signal to indicate the maximum charge current available from the EVSE.
Earth (Ground) Fault Protection
Earth fault protection is particularly important for EVSEs since EVs are typically charged outdoors, often in wet conditions. Regulations vary by country but universally require the detection and immediate disconnection of the EVSE from the electrical supply in case of earth faults. Protection must handle both AC and DC fault currents and their combinations. EVs can send DC fault current back into the EVSE, potentially blocking AC earth fault devices.
Types of Earth Fault Protection Devices
- Residual Current Device (RCD): Detects residual (earth fault) current and isolates the circuit if it exceeds a predetermined value.
- Ground Fault Circuit Interrupter (GFCI): The North American equivalent of an RCD with lower tripping currents for personnel protection.
- Residual Direct Current Detecting Device (RDC-DD): Monitors DC residual current, detecting when it exceeds a set value. There are two types:
- RDC-M (Monitor): Linked to a separate switching device; monitors DC residual current. Must be integrated by the EVSE manufacturer.
- RDC-PD (Protection Device): Monitors both AC and DC residual currents and includes an isolation mechanism, providing comprehensive earth fault protection.
RDCs monitor DC residual currents, while RCDs handle AC residual currents. When using an RDC-M, a separate RCD/GFCI is needed for AC residual current detection. Ensuring your EVSE complies with local regulations and incorporates proper fault protection is vital for safe and efficient EV charging.
By understanding these components and their functionalities, you can better assess and select the appropriate electric car charger testers to ensure optimal performance and safety.
