146 Electrical Power Systems Technology
oped by three-phase alternators, and then converted to single-phase elec-
tricity by the power distribution system. There are two basic methods that
can be used to produce single-phase AC. One method is called the rotat-
ing-armature method, and the other is the rotating field method. These meth-
ods are illustrated in Figure 6-5.
Rotating-armature Method
In the rotating-armature method, shown in Figure 6-4A, an AC voltage
is induced into the conductors of the rotating part of the machine. The elec-
tromagnetic field is developed by a set of stationary pole pieces. Relative
motion between the conductors and the magnetic field is provided by a
prime mover, or mechanical energy source, connected to the shaft (which
is a part of the rotor assembly). Prime movers may be steam turbines, gas
turbines, or hydraulic turbines, gasoline engines, diesel engines, or pos-
sibly gas engines, or electric motors. Remember that all generators con-
vert mechanical energy into electrical energy, as shown in Figure 6-6. Only
Figure 6-5. The two basic methods of generating single-phase alternating cur-
rent: (A) Rotating-armature method, (B) Rotating-field method