EVITP Technology and Equipment 3 — Questions and Answers
Question 1: Which standard governs the wireless charging (inductive) of electric vehicles in North America?
- SAE J1772
- SAE J2954 (Correct answer)
- IEC 62196-3
- CHAdeMO 3.0
Correct answer: SAE J2954
SAE J2954 is the standard that defines wireless power transfer (WPT) for light-duty plug-in and electric vehicles, including interoperability and safety requirements.
Question 2: In a bidirectional charging setup (V2G), what additional capability must the EVSE hardware include compared to a standard charger?
- Higher amperage output up to 200 A
- An inverter capable of converting DC from the vehicle battery back to AC grid power (Correct answer)
- A second pilot signal line for reverse communication
- A second utility meter for net metering
Correct answer: An inverter capable of converting DC from the vehicle battery back to AC grid power
V2G (Vehicle-to-Grid) requires the EVSE to include an inverter so that DC energy from the vehicle battery can be converted back to AC for export to the grid.
Question 3: What is the maximum voltage output specified for a CHAdeMO DC fast charger?
- 400 V DC
- 500 V DC (Correct answer)
- 1000 V DC
- 800 V DC
Correct answer: 500 V DC
Standard CHAdeMO chargers specify a maximum output of 500 V DC, though the newer CHAdeMO 3.0 (ChaoJi) extends this significantly.
Question 4: Which type of thermal management is most effective for protecting EVSE power electronics in high-ambient-temperature outdoor installations?
- Passive convection cooling with louvered vents
- Forced air cooling with filtered fans
- Liquid cooling of internal power modules (Correct answer)
- Thermoelectric (Peltier) cooling
Correct answer: Liquid cooling of internal power modules
Liquid cooling of internal power modules provides the most effective thermal management for high-power EVSE in hot outdoor environments, enabling sustained output without derating.
Question 5: What does the term 'charging curve' refer to in the context of DC fast charging?
- The physical cable routing from the EVSE to the vehicle
- The relationship between the vehicle's state of charge and the accepted charge power over time (Correct answer)
- The voltage drop across the EVSE power cable during a session
- The duty cycle waveform of the pilot signal
Correct answer: The relationship between the vehicle's state of charge and the accepted charge power over time
The charging curve describes how accepted power (and current) changes as the vehicle's battery state of charge increases during a fast-charge session.
Question 6: Which component in a networked EVSE is primarily responsible for secure user authentication and session authorization?
- The energy meter module
- The RFID reader or network gateway with backend OCPP authorization (Correct answer)
- The ground fault detection circuit
- The pilot signal oscillator
Correct answer: The RFID reader or network gateway with backend OCPP authorization
RFID readers combined with backend OCPP authorization allow the network to verify user credentials before enabling a charging session.
Question 7: What is the purpose of the pre-charge circuit in a DC fast charger before closing the main contactors?
- Test the GFCI before every session
- Slowly raise the DC bus voltage to match the vehicle battery voltage and prevent inrush current damage (Correct answer)
- Verify the communication link with the vehicle is active
- Calibrate the revenue-grade energy meter
Correct answer: Slowly raise the DC bus voltage to match the vehicle battery voltage and prevent inrush current damage
The pre-charge circuit ramps the DC bus voltage up to the vehicle battery voltage level through a current-limiting resistor before the main contactors close, preventing damaging inrush current.
EVITP Technology and Equipment 3
Which standard governs the wireless charging (inductive) of electric vehicles in North America?