13: Single-Phase Transformer Connections for Typical Service to Buildings

 Single-Phase Transformer Connections for Typical Service to Buildings

Figure  shows a typical arrangement of bringing leads out of as  single-phase distribution transformer. 

To provide flexibility for connection, the secondary winding is arranged in two sections.

Each section has the same number of turns and, consequently, the same voltage. 

Two primary leads (H1, H2) are brought out from the top through porcelain bushings. 

Three secondary leads (X1, X2, X3)

are brought out through insulating bushings on the side of the tank, one lead from the center tap (neutral) (X2) and one from each end of the secondary coil (X1 and X3). 

Connections, as shown, are typical of

services to homes and small businesses. 

This connection provides a three-wire service that permits adequate capacity at minimum cost.

The neutral wire (X2) (center tap) is grounded. A 120-volt circuit is

between the neutral and each of the other leads, and a 240-volt circuit

is between the two ungrounded leads.