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CHAPTER 1
DIRECT CURRENT GENERATORS
LEARNING OBJECTIVES
Upon completion of the chapter you will be able to:
1. State the principle by which generators convert mechanical energy to electrical energy.
2. State the rule to be applied when you determine the direction of induced emf in a coil.
3. State the purpose of slip rings.
4. State the reason why no emf is induced in a rotating coil as it passes through a neutral plane.
5. State what component causes a generator to produce direct current rather than alternating current.
6. Identify the point at which the brush contact should change from one commutator segment to the
next.
7. State how field strength can be varied in a dc generator.
8. Describe the cause of sparking between brushes and commutator.
9. State what is meant by "armature reaction."
10. State the purpose of interpoles.
11. Explain the effect of motor reaction in a dc generator.
12. Explain the causes of armature losses.
13. List the types of armatures used in dc generators.
14. State the three classifications of dc generators.
15. State the term that applies to voltage variation from no-load to full-load conditions and how it is
expressed as a percentage.
16. State the term that describes the use of two or more generators to supply a common load.
17. State the purpose of a dc generator that has been modified to function as an amplidyne.
INTRODUCTION
A generator is a machine that converts mechanical energy into electrical energy by using the
principle of magnetic induction. This principle is explained as follows:
Whenever a conductor is moved within a magnetic field in such a way that the conductor cuts across
magnetic lines of flux, voltage is generated in the conductor.
