In the context of electrical engineering and AC (alternating current) fundamentals, "true power" refers to the actual power consumed by a circuit or device that is connected to an AC power source. True power is also known as real power or active power, and it's measured in watts (W). True power is an important concept because it represents the actual useful work done by the circuit or device, such as providing light, heat, or mechanical motion.
In an AC circuit, the voltage and current are typically sinusoidal waveforms that alternate direction periodically. Since voltage and current can be out of phase due to the characteristics of reactive components like capacitors and inductors, not all of the apparent power (the product of voltage and current) is actually used to do useful work. Some of the power is lost due to the reactive components causing phase differences between voltage and current.
The three main types of power in an AC circuit are:
Apparent Power (S): This is the product of the root mean square (RMS) voltage and RMS current in a circuit. It's measured in volt-amperes (VA) and represents the total power that is being delivered to the circuit.
True Power (P): This is the actual power consumed by the circuit and utilized for performing useful work. It's measured in watts (W). True power is the real component of the apparent power and is given by the equation: P = S * cos(θ), where θ is the phase angle between voltage and current.
Reactive Power (Q): This is the power that flows back and forth between the source and reactive components (such as capacitors and inductors) without performing any useful work. It's measured in volt-amperes reactive (VAR). Reactive power is the imaginary component of the apparent power and is given by the equation: Q = S * sin(θ), where θ is the phase angle.
In summary, true power (or real power) is the actual power that is converted into useful work in an AC circuit. It's the component of apparent power that contributes to performing tasks like producing light, heat, or mechanical motion, while reactive power represents the energy oscillating between the source and reactive components without performing useful work.