Page 605 - Basic Electrical Engineering

full-wave rectifier which converts generated ac into dc for the output circuit.
A dc generator, therefore, converts mechanical energy supplied through the
prime mover to electrical energy to be supplied from the generator armature

to an electrical load. We, of course, will need to create a magnetic field by a
field system as shown in Fig. 7.1. It can be noticed from the figure that the

magnetic poles are electromagnets fixed on a hollow cylindrical frame.
Depending on the direction of the winding and the direction of current flow

through the field windings, alternate North and South poles are formed,
creating a magnetic field inside which the cylindrical rotor called armature is

placed and is rotated.
The brush and commutator arrangement has not been shown in the figure.
The armature conductors have been shown rotated in the magnetic field by a

prime mover at N rpm (revolutions per minute).

Figure 7.1 Cross-sectional view of a four-pole dc machine

All the field–pole windings have been shown connected in series. The
direction of current flow in the pole windings are such that alternate North

and South poles have been formed. The field system have been energized by
passing current, I through their windings from a separate dc source. To
f
understand the working of a dc generator we will consider, for simplicity, a