DC Machines

Question 1

What is used to prevent motorizing of a generator?
A. reverse power relay
B. distance relay
C. differential power relay
D. sensor relay

Answer 1

reverse power relay

Question 2

The dc armature winding in which the coil sides are placed a pole pitch apart is called ___________
A. multiplex
B. full-pitch
C. fractional pitch
D. pole-pitch

Answer 2

full-pitch

Question 3

Which of the following limits the number of coils that may be placed on the armature of a DC motor or generators?
A. coil to coil arcing due to the breakdown of insulation
B. the sizes of the load on the motor
C. the type of winding used
D. the number of poles

Answer 3

coil to coil arcing due to the breakdown of insulation

Question 4

Which of the following depends on the electromotive force of a DC generator?
A. commutation
B. brush contact
C. speed
D. frequency

Answer 4

speed

Question 5

What is the effects on current flow does in reversing the direction of movement of a conductor in the magnetic field of a generator?
A. It will increase the current flow.
B. It reverses the direction of current flow
C. It will neutralizes the current flow.
D. It has no effect on the current flow.

Answer 5

It reverses the direction of current flow

Question 6

Which of these is not a factor in determining the speed of a dc motor?
A. Strength of armature circuit magnetic field
B. Strength of magnetic field produced by the field coils
C. The load on the motor
D. The thickness of the commutator bars

Answer 6

The thickness of the commutator bars

Question 7

Which dc motor cannot be used without a load connected to it?
A. Shunt
B. Series
C. Compound
D. Universal

Answer 7

Series

Question 8

In a DC Motor, what is the definition of “field resistance”?
A. It is load resistance seen by a generator without considering inductance
B. It is the resistance of the excitation circuit
C. It is the resistance of the armature windings plus the load resistance
D. It is the static resistance of the motor

Answer 8

It is the resistance of the excitation circuit

Question 9

Modern locomotives are powered by DC motors driven by DC generators. Those are, in turn, driven by diesel engines. WHich of the following is the reason for using such a configuration instead of AC generator-motor sets?
A. The DC equipment is significantly less expensive.
B. The DC configuration provides high torque and good incremental power at low speeds, and performs equally well at high speeds.
C. Historically, the DC engines configuration has been used. There is no reason to change this.
D. By using the DC equipment, the power factor problems associated with AC equipment are avoided

Answer 9

The DC configuration provides high torque and good incremental power at low speeds, and performs equally well at high speeds.