SureDenPower Factor
P = Vrms Irms cosθ
The term cosθ is known as Power Factor and determines the power consumed by AC circuit.
P = VI cosθ V and I are considered to be rms values.
For impedance triangle cosθ = R/Z
And I = V/Z
P = V.I cosθ
= I Z.I = R/Z = I = R
Power Factor of various compounds:-
cosθ = R/Z
(1) for Pure resistance θ = 0 ∴ cosθ = 1
Power factor = 1
(2) for Pure inductance θ = (π/2) ∴ cosθ = 0
cosθ = R/Z = 0/Z = 0
No power consumed
(3) for Pure capacitor θ = (π/2) ∴ cosθ = 0
Power factor = 0
No power consumed
(4) for L – R circuit
0 < θ < (π/2)
1 > cosθ > 0
cosθ = R/Z = R(R2 + XL2)1/2
(5) for CR – circuit
0 < θ < (π/2) 1 > cosθ > 0
(6) for L – C circuit
θ = ± (π/2) --> cosθ = 0
(7) for LCR circuit
0 ≤ θ < (π/2) 1 ≥ cosθ > 0
cosθ = R/(R2 + (XL – XC)2)1/2