7.6
Power Factor
The power factor is the ratio of the active power to the apparent power.
It is determined by the phase difference between the voltage and current, which arise due to the presence of reactive elements in the circuit.
An analogy can be drawn with a glass of coffee, where the coffee symbolizes the useful active power, and the foam represents the reactive power, which, despite not performing real work, is utilized in certain appliances.
The cost covers the entire glass. For maximum value, the reactive power should be reduced to bring the power factor close to unity.
For a purely resistive load, in-phase voltage and current yield a unity power factor, where apparent power equals active power.
For a purely reactive load, the power factor is zero, implying the active power is zero.
Between these extremes, the power factor is either leading or lagging. A leading power factor indicates that the current leads the voltage, implying a capacitive load.
A lagging power factor signifies that the current lags behind the voltage, indicating an inductive load.
The power factor is defined as the ratio of average (or active) power to apparent power, as illustrated by the relation
The term in bracket, (θv - θi), is referred to as the power factor angle, as it represents the angle whose cosine yields the power factor. If V represents the voltage across the load and Ⅰ signifies the current flowing through it, the power factor angle equates to the angle of the load impedance. Essentially, the power factor is the cosine of the phase difference between the voltage and current, as well as the cosine of the angle of the load impedance.
From the above equation, it can be inferred that the power factor is the multiplier for the apparent power to yield the real or average power. The power factor's value ranges between zero and one. When dealing with a purely resistive load, the voltage and current are in phase, resulting in a power factor angle (θv - θi) = 0 and a power factor = 1. This indicates that the apparent power equals the average power. For a purely reactive load, (θv - θi) = ±90o and a power factor = 0, making the power zero. Between these two extremes, the power factor is said to be either leading or lagging. A leading power factor suggests that the current precedes the voltage, indicating a capacitive load, while a lagging power factor suggests that the current follows the voltage, indicating an inductive load. The power factor significantly impacts the electricity bills consumers pay to their utility companies.
The power factor is the ratio of the active power to the apparent power.
It is determined by the phase difference between the voltage and current, which arise due to the presence of reactive elements in the circuit.
An analogy can be drawn with a glass of coffee, where the coffee symbolizes the useful active power, and the foam represents the reactive power, which, despite not performing real work, is utilized in certain appliances.
The cost covers the entire glass. For maximum value, the reactive power should be reduced to bring the power factor close to unity.
For a purely resistive load, in-phase voltage and current yield a unity power factor, where apparent power equals active power.
For a purely reactive load, the power factor is zero, implying the active power is zero.
Between these extremes, the power factor is either leading or lagging. A leading power factor indicates that the current leads the voltage, implying a capacitive load.
A lagging power factor signifies that the current lags behind the voltage, indicating an inductive load.
From Chapter 7:
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