Drivetrain & Transmission 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 Drivetrain & Transmission flashcards as text
What is the purpose of the 'notch' positions on a locomotive throttle?
Answer: They represent discrete power levels that set engine RPM and generator output
Each throttle notch (1–8) commands a specific engine RPM and generator excitation level, producing a corresponding level of horsepower output.
When a locomotive engineer observes excessive traction motor temperatures during a long upgrade, the RECOMMENDED action is to:
Answer: Reduce throttle to lower motor current and allow temperatures to decrease
Reducing throttle decreases current through the traction motors, lowering heat generation and allowing motor temperatures to return to safe operating range.
In locomotive terminology, what does 'tractive effort' measure?
Answer: The drawbar pull force available to move a train, measured in pounds
Tractive effort is the horizontal pulling force exerted at the rail-wheel contact point, typically expressed in pounds, used to overcome train resistance and grade.
What causes 'hunting' in a locomotive truck, and how does it affect drivetrain components?
Answer: Lateral oscillation of the truck assembly causing varying forces on axle gear meshes
Truck hunting is a speed-dependent lateral oscillation that imposes cyclic lateral forces on axle bearings and gear meshes, potentially causing accelerated wear.
On a diesel-electric locomotive, the traction motors are classified as what type of electric motor?
Answer: DC series-wound motors in older locomotives, AC induction motors in newer units
Older diesel-electrics used DC series-wound traction motors; modern AC traction locomotives use three-phase AC induction motors for superior adhesion and reliability.
What advantage do AC traction motors provide over DC traction motors in locomotive drivetrains?
Answer: AC motors can be allowed to slip briefly without damage, enabling better adhesion utilization
AC induction motors tolerate controlled slip without armature damage, allowing sophisticated adhesion control systems to extract maximum tractive effort from available rail friction.
What is the role of the 'excitation' control in a diesel-electric locomotive's drivetrain power flow?
Answer: It regulates main generator field current to control power output at each throttle notch
Excitation control varies the current in the main generator's field windings, which determines the generator's voltage and power output at any given engine speed.