Electric Vehicle Systems & Powertrains Flashcards
7 cards from real EVT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electric Vehicle Systems & Powertrains flashcards as text
What is the role of the onboard charger (OBC) in an electric vehicle?
Answer: Convert AC grid power to DC to charge the high-voltage battery
The OBC rectifies and conditions AC power from Level 1 or Level 2 charging sources into regulated DC voltage to charge the traction battery pack.
Why is insulation resistance monitoring critical in an EV high-voltage system?
Answer: It detects degraded insulation that could create a shock hazard or fault between HV circuits and chassis ground
Insulation resistance monitoring (via the IMD/IRD) continuously checks that HV conductors maintain safe isolation from the vehicle chassis, alerting to insulation breakdown before a dangerous fault occurs.
In an induction motor used for EV propulsion, 'slip' refers to:
Answer: The difference between the synchronous rotating field speed and the actual rotor speed
Slip is the speed difference between the stator's rotating magnetic field (synchronous speed) and the rotor, and it is what induces the currents that create rotor torque in an induction motor.
What is a 'hairpin winding' motor, and what advantage does it offer in EVs?
Answer: A motor using rectangular copper conductors in the stator for higher slot fill and improved thermal conductivity
Hairpin windings use flat rectangular copper bars that pack more densely into stator slots, improving copper fill factor, reducing resistance, and enhancing heat transfer for higher power density.
When performing an HV system interlock check, the technician is verifying that:
Answer: The HV service disconnect and connector interlocks are intact so the system cannot energize with covers removed
HV interlock circuits detect open covers, disconnected connectors, or removed service plugs and prevent the main contactors from closing until all interlocks are confirmed closed.
What is the function of the motor control unit (MCU) / power electronics controller (PEC) in an EV?
Answer: Execute torque commands from the vehicle control unit by controlling inverter switching to regulate motor current and speed
The MCU/PEC translates driver torque requests and vehicle control unit commands into precise IGBT/MOSFET switching patterns that control motor current, torque, and speed.
In an EV using field-oriented control (FOC), what are the two current components being independently controlled?
Answer: Flux-producing (d-axis) current and torque-producing (q-axis) current
FOC decouples motor current into a d-axis component that controls rotor flux and a q-axis component that directly controls torque, enabling precise and efficient motor operation.