Basic AC Power POWER TRIANGLEPOWER TRIANGLEWhile direct current has one form of power, alternating current has three differentforms of power that are related in a unique relationship. In this chapter, you willlearn that power in AC circuits cannot be calculated in the same manner as in DCcircuits.EO 1.1 DESCRIBE the relationship between apparent, true, andreactive power by definition or by using a powertriangle.EO 1.2 DEFINE power factor as it relates to true power andapparent power.EO 1.3 Given the necessary values for voltage (E), resistance(R), reactance (X), impedance (Z), and/or current (I),CALCULATE the following power components for anAC circuit:a. True power (P)b. Apparent power (S)c. Reactive power (Q)d. Power factor (pf)EO 1.4 DEFINE the following terms:a. Leading power factorb. Lagging power factorPowerTriangleIn AC circuits, current and voltage are normally out of phase and, as a result, not all the powerproduced by the generator can be used to accomplish work. By the same token, power cannotbe calculated in AC circuits in the same manner as in DC circuits. The power triangle, shownin Figure 1, equates AC power to DC power by showing the relationship between generatoroutput (apparent power - S) in volt-amperes (VA), usable power (true power - P) in watts, andwasted or stored power (reactive power - Q) in volt-amperes-reactive (VAR). The phase angle(q) represents the inefficiency of the AC circuit and corresponds to the total reactive impedance(Z) to the current flow in the circuit.Rev. 0 Page 1 ES-09
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