High Voltage Electrical Systems & Wiring 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 High Voltage Electrical Systems & Wiring flashcards as text
What is the typical high-voltage bus operating range for a 400V-class battery electric vehicle?
Answer: 300–450V DC
Most 400V-class EVs operate their HV bus between 300–450V DC depending on the battery state of charge, with nominal voltage near 400V.
After removing the manual service disconnect, why must a technician wait before touching HV components?
Answer: To allow large bus capacitors to discharge to a safe voltage level through internal bleed resistors
Large capacitors in inverters and DC/DC converters store significant energy that remains after the MSD is removed; waiting allows them to discharge to a safe voltage through internal bleed resistors.
What does an isolation fault code in an EV high-voltage system indicate?
Answer: An unintended electrical path exists between the HV circuit and the vehicle chassis
An isolation fault means the insulation resistance between the HV circuit and chassis has dropped below the safe threshold, creating a path that could allow dangerous current to flow through the vehicle body.
What does applying a lockout/tagout (LOTO) procedure during EV high-voltage service ensure?
Answer: The HV system cannot be accidentally re-energized while a technician is working on it
LOTO procedures physically lock the MSD in the removed position and apply a tag, preventing any other person from re-energizing the HV system while a technician is actively working on it.
Which tool provides a non-contact method of confirming HV absence on EV cables before making direct contact?
Answer: Non-contact high-voltage tester rated for the system voltage
A non-contact HV tester detects the electric field around energized HV cables without requiring direct contact, providing a safer first check before using a contact voltmeter.
When routing high-voltage wiring near heat sources in a hybrid vehicle, what is the primary safety concern?
Answer: Heat degradation of cable insulation leading to potential isolation failure
Sustained heat degrades the dielectric properties of HV cable insulation over time, which can lead to insulation breakdown, isolation faults, and shock or fire hazards.
What is the correct method for repairing a damaged high-voltage cable in an EV when a manufacturer-approved procedure exists?
Answer: Manufacturer-approved HV splice kit that restores shielding continuity and rated insulation
HV cable repairs must use manufacturer-approved splice kits that restore shielding continuity, maintain original insulation voltage ratings, and meet the cable's full current and voltage specifications.