POWER TRIANGLE

Basic AC Power POWER TRIANGLE POWER TRIANGLE While direct current has one form of power, alternating current has three different forms of power that are related in a unique relationship. In this chapter, you will learn that power in AC circuits cannot be calculated in the same manner as in DC circuits. EO 1.1 DESCRIBE the relationship between apparent, true, and reactive power by definition or by using a power triangle. EO 1.2 DEFINE power factor as it relates to true power and apparent 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 an AC 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 factor b. Lagging power factor Power Triangle In AC circuits, current and voltage are normally out of phase and, as a result, not all the power produced by the generator can be used to accomplish work. By the same token, power cannot be calculated in AC circuits in the same manner as in DC circuits. The power triangle, shown in Figure 1, equates AC power to DC power by showing the relationship between generator output (apparent power - S) in volt-amperes (VA), usable power (true power - P) in watts, and wasted 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