DC GeneratorsIntroductionAlthough A Far Greater Percentage
D.C. Generators
Introduction
Although a far greater percentage of the electrical machines in service are a.c. Machines, the D.C. machines are of considerable industrial importance. The principal advantage of the D.C. machine, particularly the D.C. motor, is that it provides a fine control of speed. Such an advantage is not claimed by any a.c. motor. However, D.C. generators are not as common as they used to be, because direct current, when required, is mainly obtained from an a.c. supply by the use of rectifiers. Nevertheless, an understanding of D.C. generator is important because it represents a logical introduction to the behavior of D.C. motors. Indeed many D.C. motors in industry actually operate as D.C. generators for a brief period. In this chapter, we shall deal with various aspects of D.C. Generators.
A generator is a machine that converts mechanical energy into electrical energy by using the principle of magnetic induction.
DC generator or direct current generator generates a voltage when speed and flux are met. This machine is called a unidirectional (dynamo).It consists of the same basic elements as a simple AC generator like the multi-turn coil rotating uniformly in a magnetic field .The output of which is a series of emf pulses, all in the same positive direction resulting in an average EMF developed across the load. Increasing the number of coils thereby smoothen the output providing more pulses at each revolution.
The generated voltage depends upon the number of poles and armature winding turns. It has armature with iron core and air gap which is uniform the vicinity of the center of the pole and which becomes larger as the pole tips are approached. This construction gives a uniform flux distribution under the main parts of the pole face with a reduction in the flux at pole tips. To produce an emf the conductor must cut the magnetic lines of force. The single coil is connected to two copper segments by carbon brushes. As before the output
Introduction
Although a far greater percentage of the electrical machines in service are a.c. Machines, the D.C. machines are of considerable industrial importance. The principal advantage of the D.C. machine, particularly the D.C. motor, is that it provides a fine control of speed. Such an advantage is not claimed by any a.c. motor. However, D.C. generators are not as common as they used to be, because direct current, when required, is mainly obtained from an a.c. supply by the use of rectifiers. Nevertheless, an understanding of D.C. generator is important because it represents a logical introduction to the behavior of D.C. motors. Indeed many D.C. motors in industry actually operate as D.C. generators for a brief period. In this chapter, we shall deal with various aspects of D.C. Generators.
A generator is a machine that converts mechanical energy into electrical energy by using the principle of magnetic induction.
DC generator or direct current generator generates a voltage when speed and flux are met. This machine is called a unidirectional (dynamo).It consists of the same basic elements as a simple AC generator like the multi-turn coil rotating uniformly in a magnetic field .The output of which is a series of emf pulses, all in the same positive direction resulting in an average EMF developed across the load. Increasing the number of coils thereby smoothen the output providing more pulses at each revolution.
The generated voltage depends upon the number of poles and armature winding turns. It has armature with iron core and air gap which is uniform the vicinity of the center of the pole and which becomes larger as the pole tips are approached. This construction gives a uniform flux distribution under the main parts of the pole face with a reduction in the flux at pole tips. To produce an emf the conductor must cut the magnetic lines of force. The single coil is connected to two copper segments by carbon brushes. As before the output