Electrical & Electronic Systems Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical & Electronic Systems flashcards as text
On an AC traction locomotive, what component converts DC link voltage to variable-frequency AC for the traction motors?
Answer: Inverter (IGBT propulsion inverter)
IGBT-based propulsion inverters convert the DC link voltage to variable-frequency, variable-voltage AC power to control AC traction motor speed and torque.
What is the function of the 'alerter' (deadman) system on a locomotive?
Answer: Ensure the engineer is awake and alert by requiring periodic acknowledgment
The alerter system monitors for engineer inactivity and applies brakes if the engineer does not acknowledge a periodic alarm within a set time interval.
Which condition would cause a locomotive's ground fault indicator to illuminate?
Answer: Unintended electrical continuity between a traction circuit conductor and the locomotive frame
A ground fault occurs when a normally isolated high-voltage traction circuit conductor makes unintended contact with the grounded locomotive frame.
What does 'dynamic brake grid' refer to on a locomotive?
Answer: Resistor banks that dissipate energy generated during dynamic braking as heat
During dynamic braking, traction motors acting as generators produce electrical energy that is dissipated as heat through resistor grids (dynamic brake grids) in the equipment bays.
What is the correct procedure if a cab signal system fails en route?
Answer: Notify dispatch, obtain authority to proceed, and operate according to applicable rules for signal failure
A cab signal failure requires notifying the dispatcher, obtaining proper operating authority, and following railroad rules for operating without cab signals.
On a diesel-electric locomotive, what is the purpose of the 'companion alternator' (or auxiliary alternator)?
Answer: Supply electrical power for auxiliary loads such as cooling fans, air compressors, and lighting
The companion or auxiliary alternator provides lower-voltage AC power for locomotive auxiliaries like cooling fans, compressors, and cab heating/lighting systems.
What sensor is used to measure the rotational speed of traction motor armatures (or rotor speed on AC motors) for wheel slip detection?
Answer: Speed pickup (tachometer-generator or speed sensor)
Speed pickups (tachometer-generators or digital speed sensors) mounted on axles or motors measure rotational speed so the control system can detect axle speed differentials indicating wheel slip.