AC Impedance:
- AC circuits contain both resistance and reactance that are combined together to give a total impedance (Z) that limits current flow around the circuit.
- Impedance is not equal to the algebraic sum of the resistive and reactive ohmic values as a pure resistance and pure reactance are 90 degree out of phase with each other.
- But we can use this 90 degree phase difference as the sides of a right angled triangle, called an impedance triangle, with the impedance being the hypotenuse as determined by Pythagoras theorem.
- This geometric relationship between resistance, reactance and impedance can be represented visually by the use of an impedance triangle as shown.
- Impedance, which is the vector sum of the resistance and reactance, has not only a magnitude (Z) but it also has a phase angle, which represents the phase difference between the resistance and the reactance.
Power Factor in AC Circuits:
The power factor is calculated as the ratio of the real power to the apparent power because this ratio equals to cosine of phase angle.
Power factor, is an important part of an AC circuit that can also be expressed in terms of circuit impedance or circuit power.
Power factor is defined as the ratio of real power (P) to apparent power (S), and is generally expressed as either a decimal value, for example 0.95, or as a percentage: 95percentage.
Power factor angle defines the phase angle between the current and voltage waveforms, were I and V are the magnitudes of rms values of the current and voltage.
Power Factor is also defined as the ratio of Resistance & Magnitude of Impedance.
cos φ= PowerFactor=R/Z
If the phase angle is positive then voltage leads the current and Power factor becomes lagging.
If the phase angle is negative then current leads the voltage and Power factor becomes leading.
