Single Phase Transformers
The most common single phase service is provided from one single-phase transformer, used mainly for residential and small commercial service at both 120 and 240 volts. In supplying single-phase loads, the service drop almost always consist of two load, or service lines, and a neutral. If the transformer has three low-voltage bushings, the center bushing is always the neutral, to which the neutral line is connected. The two service lines are connected to the remaining two bushings. From such a connection, two different single-phase voltages are available. The voltage between the two "hot" legs of the service is 240 and the voltage between either "hot" leg and the neutral is 120. Single phase service can easily be provided from either Wye or Delta distribution systems by using the appropriate type of transformer.