AC GENERATOR OPERATION
AC Generator Connections
Figure 8 Delta Connection
As shown in Figure 7, there are six leads from the
armature of a three-phase generator, and the output is
connected to an external load. In actual practice, the
windings are connected together, and only three leads are
brought out and connected to the external load.
Two means are available to connect the three armature
windings. In one type of connection, the windings are
connected in series, or delta-connected (D) (Figure 8).
In a delta-connected generator, the voltage between any
two of the phases, called line voltage, is the same as the
voltage generated in any one phase. As shown in Figure 9, the three phase voltages are equal,
as are the three line voltages. The current in any line is
times the phase current. You can
see that a delta-connected generator provides an increase in current, but no increase in voltage.
An advantage of the delta-connected AC generator is that if one phase becomes damaged or
Figure 9 Characteristics of a Delta-Connected Generator
open, the remaining two phases can still deliver three-phase power. The capacity of the generator
is reduced to 57.7% of what it was with all three phases in operation.