LEC Drivetrain & Transmission 2

Question 1

What is the primary function of a locomotive's main generator (alternator) in a diesel-electric drivetrain?

Accepted Answer

Convert diesel engine mechanical output to electrical power for traction motors

Answer

The main generator converts the diesel engine's mechanical energy into electrical power that feeds the traction motors on each axle.

Question 2

In a diesel-electric locomotive, what component controls the amount of electrical power delivered to the traction motors?

Accepted Answer

The load regulator (throttle control system)

Answer

The load regulator adjusts field excitation and generator output to control power delivered to traction motors in response to throttle position.

Question 3

What happens to wheel slip in a diesel-electric locomotive when tractive effort exceeds the rail-wheel adhesion limit?

Accepted Answer

The traction motor speeds up unloaded, causing wheel spin

Answer

When adhesion is exceeded, the drive wheels lose traction and spin freely, causing the traction motor to accelerate rapidly without load.

Question 4

On a six-axle diesel-electric locomotive, how are traction motors typically connected electrically during starting operations?

Accepted Answer

Motors grouped in series-parallel combinations for high starting torque

Answer

Series-parallel groupings allow high torque at low speed by limiting current through individual motors while maintaining adequate voltage.

Question 5

What is the purpose of the transition in a diesel-electric locomotive's power circuit?

Accepted Answer

To change traction motor connections from series to parallel as speed increases

Answer

Transition reconnects traction motors from series to parallel to allow higher speeds while maintaining efficient power utilization.

(LEC) Locomotive Engineer Certification Practice Test