Wye and delta configurations: The windings of a three-phase ac power source can be connected in either a wye configuration, or a delta configuration. The configuration names are derived from the appearance of the circuit drawings representing the configurations, i.e., the letter Y for the wye configuration and the Greek letter delta for the delta configuration. The connections for each configuration are shown in Figurea. Each type of configuration has definite electrical characteristics.

As Figure a shows, in a wye-connected circuit, one end of each of the three windings (or phases) of the three-phase ac power source is connected to a
common point called the neutral. No current flows in the neutral because the currents flowing in the three windings (i.e., the phase currents) cancel each other
out when the system is balanced. Wye connected systems typically consist of three or four wires (these wires connect to points A, B, C, and N in FigureA(1)),
depending on whether or not the neutral line is present.

Figureb shows that, in a delta-connected circuit, the three windings of the three-phase ac power source are connected one to another, forming a triangle.
The three line wires are connected to the three junction points of the circuit (points A, B, and C in Figureb). There is no point to which a neutral wire can be connected in a three-phase delta-connected circuit. Thus, deltaconnected systems are typically three-wire systems.

Types of three-phase system configurations.