Why is the power factor not more than unity ?
The correct answer and explanation is:
The power factor in an AC electrical system cannot exceed unity (1) because of the inherent characteristics of voltage and current waveforms. Power factor is defined as the cosine of the phase angle between the voltage and current waveforms in an AC circuit. It is a measure of how effectively the current is being used to produce useful work, and it is always a number between 0 and 1.
If the power factor were to exceed 1, it would imply that the current is leading the voltage by more than 90 degrees or lagging it by more than 90 degrees, which is not physically possible in a typical AC circuit. This is because the current and voltage waveforms are sinusoidal, and the maximum phase difference between them can only be 90 degrees, either in leading or lagging. At this phase difference, the power factor is 0. If the phase angle is 0 degrees, the power factor is unity, meaning the voltage and current are perfectly in phase, and all the electrical power supplied is being used effectively.
In practical AC circuits, factors such as inductance and capacitance cause the current and voltage to shift out of phase, but even under ideal conditions, the power factor can only approach unity, not exceed it. In a purely resistive load, the power factor is 1, meaning all the power is converted into useful work. In circuits with reactive components (inductors and capacitors), the power factor decreases, as some of the energy is stored and returned to the source, rather than being converted into work.
Therefore, the power factor cannot exceed 1, as it would violate the principles of AC circuit behavior, particularly the relationship between the current, voltage, and phase angle.