Basic AC Theory AC GENERATION ANALYSISExample 2: The peak current in an AC circuit is 10 amps. What is the average value ofcurrent in the circuit?I_{av} = 0.637 I_{max}I_{av} = 0.637 (10 amps)I_{av} = 6.37 ampsPhaseAnglePhase angle is the fraction of a cycle, in degrees, that has gone by since a voltage or current haspassed through a given value. The given value is normally zero. Referring back to Figure 3,take point 1 as the starting point or zero phase. The phase at Point 2 is 30°, Point 3 is 60°, Point4 is 90°, and so on, until Point 13 where the phase is 360°, or zero. A term more commonlyused is phase difference. The phase difference can be used to describe two different voltages thathave the same frequency, which pass through zero values in the same direction at different times.In Figure 5, the angles along the axis indicate the phases of voltages e_{1} and e_{2} at any point intime. At 120°, e_{1}passes through the zero value, which is 60° ahead of e_{2}(e_{2}equals zero at180°). The voltage e_{1} is said to lead e_{2} by 60 electrical degrees, or it can be said that e_{2} lags e_{1}by 60 electrical degrees.Figure 5 Phase RelationshipRev. 0 Page 7 ES-07

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