Power System Fundamentals 53
voltage diagram is shown in Figure 2-21.
In Figure 2-20, poles A’, B’, and C’ represent the beginnings of each
of the phase windings, while poles A, B, and C represent the ends of each
of the windings. These windings may be connected in either of two ways.
These methods of connection, called the wye configuration and the delta
configuration, are the basic types of three-phase power systems. These
three-phase connections are shown schematically in Figure 2-22. Keep in
mind that these methods of connection apply not only to three-phase AC
generators, but also to three-phase transformer windings and three-phase
motor windings.
In the wye connection of Figure 2-22A, the beginnings or the ends of
each winding are connected together. The other sides of the windings be-
come the AC lines from the generator. The voltage across the AC lines (VL)
is equal to the square root of 3 (1.73) multiplied by the voltage across the
phase windings (VP), or:VL = VP × 1.73.Figure 2-20. Simplified drawing showing the basic construction of a three-phase
AC alternator