TABLE OF CONTENTS From our discussion in Chapter 3, it should be obvious that there are two types of rotating electric energy conversion machines the direct-current (dc) machines and the alternating-current (ac) machines. When a rotating machine converts electric energy into mechanical energy, it is called a motor. A generator, on the other hand, converts mechanical energy into electric energy. Hence, there are dc motors, dc generators, ac motors, and ac generators. A significant portion of this book is devoted to the study of these machines.
The word machine is commonly used to explain features that are common to both the motor and the generator. Quite often, a given machine can be operated as either a motor or a generator without making any modifications. This is especially true for all dc machines.
We commit this chapter entirely to the study of dc generators and reserve discussion of dc motors for the next chapter. In addition, we limit our discussion to the steady-state performance characteristics of the machine. Transient behavior is analyzed in a later chapter.
In a dc machine, the uniform magnetic flux is established by fixed poles mounted on the inside of the stationary member called the stator. We may either use permanent magnets as the poles or wind the field windings (excitation coils) around the poles. One of the major advantages of a wound machine is that we can control the flux in the machine by regulating the direct current in the field winding. The...
