Mechanical and Electrical 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 Mechanical and Electrical Systems flashcards as text
What is the primary function of the dynamic brake grid resistors on a diesel-electric locomotive?
Answer: Dissipate heat produced by dynamic braking current
Grid resistors convert electrical energy from dynamic braking into heat, which is then dissipated into the atmosphere.
On a modern AC traction locomotive, what device converts the alternator's AC output to DC before inverters redistribute power to the traction motors?
Answer: Rectifier
A rectifier converts the main alternator's AC output to DC, which inverters then convert back to variable-frequency AC for the AC traction motors.
A locomotive's air compressor fails to build pressure. Which system is most immediately affected?
Answer: Automatic and independent brakes
The automatic and independent brake systems rely on compressed air; without adequate pressure, brakes cannot be applied or released properly.
What does the term 'transition' refer to in the context of diesel-electric locomotive operation?
Answer: Changing traction motor electrical connections to optimize power at different speeds
Transition changes traction motor connections (series to parallel or changes in field strength) to deliver optimum tractive effort across different speed ranges.
Which safety device prevents a locomotive engine from overspeeding?
Answer: Engine overspeed governor
The overspeed governor shuts down the engine if RPM exceeds a safe limit, preventing mechanical damage to the prime mover.
What is indicated when the 'Ground Relay' trips on a diesel-electric locomotive?
Answer: An electrical fault to ground has occurred in the power circuit
A ground relay trip indicates an unintended electrical path to ground in the high-voltage traction circuit, requiring isolation before proceeding.
On a diesel locomotive, what is the purpose of the 'load regulator' (or load control)?
Answer: Match generator electrical load to engine horsepower to prevent stalling
The load regulator adjusts generator excitation to balance electrical load with available engine horsepower, preventing the engine from stalling under heavy loads.