EVITP Technology and Equipment 2 — Questions and Answers
Question 1: Which communication protocol is most commonly used by EVSE to communicate with the electric vehicle during a DC fast charge session?
- Modbus RTU
- CAN bus
- Combined Charging System (CCS) PLC (Correct answer)
- ZigBee
Correct answer: Combined Charging System (CCS) PLC
CCS uses Power Line Communication (PLC) over the pilot line to enable the vehicle and EVSE to negotiate charging parameters during DC fast charging.
Question 2: What is the purpose of the contactor in a DC fast charging station?
- Regulate output voltage to the vehicle
- Isolate high-voltage DC from the output connector when not charging (Correct answer)
- Convert AC input power to DC output power
- Measure energy delivered to the vehicle
Correct answer: Isolate high-voltage DC from the output connector when not charging
The contactor is a high-current switch that physically connects or disconnects the DC bus from the charging connector, ensuring safety when the connector is not engaged.
Question 3: In an EVSE network management system, what does OCPP stand for?
- Open Charge Point Protocol (Correct answer)
- Optimized Charging Power Process
- Outbound Connector Power Protocol
- Operational Charging Payment Platform
Correct answer: Open Charge Point Protocol
OCPP (Open Charge Point Protocol) is an open standard that allows EVSE hardware from different manufacturers to communicate with a common network management backend.
Question 4: A technician notices a Level 2 EVSE is delivering only 16 A instead of the rated 32 A. Which component, if faulty, would most likely cause this output reduction?
- The ground fault circuit interrupter (GFCI)
- The pilot signal resistor inside the vehicle's onboard charger
- A failed or thermally derated power relay in the EVSE (Correct answer)
- The utility revenue meter upstream of the panel
Correct answer: A failed or thermally derated power relay in the EVSE
A failed or overheated relay/contactor in the EVSE can cause it to thermally derate, limiting current output to protect the hardware.
Question 5: What is the typical pilot signal frequency used in SAE J1772 EVSE-to-vehicle communication?
- 50 Hz
- 60 Hz
- 1 kHz (Correct answer)
- 10 kHz
Correct answer: 1 kHz
SAE J1772 specifies a 1 kHz pilot signal used on the control pilot line to communicate maximum available current and charger state to the vehicle.
Question 6: Which insulation resistance test value is considered the minimum acceptable when testing EVSE wiring before energizing a new installation?
- 1 MΩ (Correct answer)
- 100 kΩ
- 500 kΩ
- 10 MΩ
Correct answer: 1 MΩ
A minimum insulation resistance of 1 MΩ (megohm) is generally required to confirm that wiring insulation is intact and safe to energize.
Question 7: What does the duty cycle of the SAE J1772 pilot signal indicate to the electric vehicle?
- The vehicle's state of charge
- The maximum current the EVSE can supply (Correct answer)
- The voltage level available at the connector
- The remaining session time authorized
Correct answer: The maximum current the EVSE can supply
The duty cycle of the 1 kHz pilot signal encodes the maximum available current: for example, a 50% duty cycle indicates 24 A available.
EVITP Technology and Equipment 2
Which communication protocol is most commonly used by EVSE to communicate with the electric vehicle during a DC fast charge session?