By definition, " The ratio between actual power dissipated by an AC circuit to the product of r.m.s. values of voltage & current ".
This can be simplified as the ratio of active power (kW) to apparent power (kVA). The difference between kW & kVA is due to reactance in the circuit & represents power that does no useful work. Power factor indicates how efficient an electrical system is, a system which has minimum losses.
Power factor varies between -1 to +1. the negative PF represents a capacitive load whereas a positive PF represents inductive load.
Power factor or true power factor consists of two components, viz.,
1) Displacement power factor :
This PF represents the phase difference between voltage & current sine waveforms. Ideally voltage & current waveforms are in phase but due to inductive/capacitive nature of load, there is a phase difference between voltage & current waveforms.
Displacement PF can be improved by using shunt reactors & series capacitors of appropriate combination & rating to maintain displacement PF.
Displacement PF is said to be worsened when either capacitive or inductive component is greater than the other one which drops down from 1 towards 0.
2) Distortion power factor :
This PF signifies the presence to harmonics in the system. Greater the harmonics in the system worse is the distortion PF.
Distortion PF can be improved by adding detuning reactors in series with capacitors in case the THD% is low. In case of higher THD% levels, active harmonics filter (AHF) is to be used.
Distortion PF is worsened with increase in THD% in the system which makes PF drop down from 0 to 1
3) True PF :
True PF comprises the effect of phase difference between voltage & current, reactance in the system and also harmonics in the system. In simple words, true PF gives an idea of total losses in the system.
True PF = Displacement PF x Distortion PF
From the equation it is clear that to maintain true PF at optimum level it is necessary to maintain both the PFs at their optimum level.
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