Summary of Units 1-4

OBJECTIVE

To give the learner/learner an opportunity to evaluate the knowledge and understanding acquired in the study of the previous four units.

Select the correct answer for each of the following statements.

1. A generator series field diverter rheostat is always connected:

a. in parallel with the series field.

b. in series with the series field.

c. directly across the line.

d. between the armature and the series field.

2. The voltage of an over-compounded generator:

a. decreases as the load increases.

b. decreases as the load remains constant.

c. increases as the load remains constant.

d. increases as the load increases.

3. Brushes of a dc generator ride on the:

a. commutator. c. shaft.

b. armature. d. commutating pole.

4. The field pole of a dc generator or motor is constructed with an iron core to:

a. decrease the magnetic flux.

b. increase and concentrate the magnetic flux.

c. decrease the residual magnetism.

d. increase the eddy currents.

5. A generator with terminal markings A1 — A2, F1 — F2, S1 — S2 is a:

a. separately-excited generator. c. series generator.

b. shunt generator. d. compound generator.

6. The field core of a dc generator is:

a. the round part of the rotating field.

b. wound with wire.

c. usually round on large machines.

d. the part of the generator that holds the armature in place.

7. In self-excited dc generators, initial field excitation is produced by:

a. current in the coils. c. magnetic flux.

b. moving the field. d. residual magnetism.

8. DC generators and motors have:

a. one pole. c. pairs of poles.

b. two poles. d. four poles.

9. To re-establish the magnetic field of a generator where the magnetic field has been lost, you must:

a. Run the generator above rated speed.

b. Reverse the connections to the shunt field.

c. Apply DC to the shunt field coils.

d. Attach a permanent magnet to the armature.

10. If a generator is over-compounded and you wish to decrease the degree of compounding then the diver resistance must be ___________________. (increased, decreased)

11. Write the formula for calculating the percent voltage regulation in a dc generator.

12. The preferred connection for dc compound generators is the ______ connection. (short-shunt, long-shunt).

13. The series field winding is a________ size wire than the shunt field winding.