Power systems that generate, transmit, and distribute electical power are designed to operate in the sinusoidal steady state. The standard household distribution cirucit used in the United States is the three-wirte, 240/120 V circuit shown in the accompanying figure.

The transformer is used to reduce the utility distribution voltage from 13.2 kV to 240 V. The center tap on the secondary winding provides the 120 V service. Thhe operating frequency of power systems in the United States is 60 Hz. Both 50 and 60 Hz system are found outside the United States.
The voltage ratings alluded to above are rms values. The reason for defining an rms value of a time-varying signal is explained.
Tue, May 13, 2008
0 Comments