Practice Test Geeks(EVT) Certified Electric Vehicle Technician Practice Test
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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

  1. What is 'copper loss' (I²R loss) in an EV traction motor, and how does motor design mitigate it?

    Answer: Energy lost as heat in stator windings due to current flow; reduced by using larger or more conductive copper conductors

    Copper loss is resistive heat dissipation in the stator windings (P = I²R); it is minimized by maximizing copper cross-sectional area, using high-conductivity copper, and optimizing winding layouts like hairpin designs.

  2. Why do EV manufacturers use field weakening control at high motor speeds?

    Answer: To extend motor operating speed beyond the base speed by reducing rotor flux, allowing higher RPM at reduced torque

    Above base speed, the motor's back-EMF approaches battery voltage; field weakening reduces the d-axis current to lower flux, allowing the motor to spin faster at the cost of reduced maximum torque.

  3. What is the purpose of the service disconnect (manual service disconnect, MSD) in an EV high-voltage battery pack?

    Answer: Manually interrupt the high-voltage circuit to de-energize the system for safe service

    The MSD physically breaks the HV circuit within the battery pack, isolating the high-voltage system so technicians can safely work on or near HV components.

  4. In a switched reluctance motor (SRM) used in some EVs, torque is produced by:

    Answer: The tendency of the rotor's salient poles to align with the energized stator poles, minimizing magnetic reluctance

    SRMs have no magnets or windings on the rotor; torque is generated by the rotor's iron teeth being magnetically attracted toward energized stator poles (reluctance minimization).

  5. What does a positive temperature coefficient (PTC) thermistor in a motor temperature sensor do as the motor overheats?

    Answer: Its resistance increases with temperature, signaling the controller to reduce motor current or power

    A PTC thermistor's resistance rises with temperature; the MCU monitors this signal and de-rates motor output or triggers a fault to prevent thermal damage.

  6. What is 'cogging torque' in a permanent magnet motor, and why is it undesirable in EVs?

    Answer: Cyclic torque ripple caused by rotor magnets snapping to stator slot positions at low speed; undesirable because it causes vibration and noise

    Cogging torque results from the attraction between rotor magnets and stator teeth as they align; it creates periodic torque ripple most noticeable at low speeds, causing NVH (noise, vibration, harshness) issues.

  7. When an EV technician measures voltage between the HV positive bus and chassis ground after removing the MSD and finds 12V, this indicates:

    Answer: Normal safe condition—HV bus has fully discharged through internal bleed resistors

    12V between the HV bus and chassis after MSD removal and adequate discharge time indicates the high-voltage capacitors have discharged to the level of the 12V auxiliary system, confirming the HV bus is safe.