Electronics - RLC Circuits and Resonance - Discussion

Power Factor = (True Power/Apparent Power).

TP = I^2*R.

AP = V*I.

Cos(phi) = PF.

Why is the phase angle negative here? Can anyone please explain?

In a parallel circuit the voltage is the same across all the components, so we have to work with the currents, which are V/R, V/Xc and V/XL. The current leads V in the capacitor (+90) , lags V in the inductor (-90) and is in phase in the resistor (0).

Total current is the vector sum of the three components (I = sqrt (Ir^2 + (Ic-IL)^2) , and the phase angle is tan^-1 ((Ic-IL)/Ir. Since IC<IL, this will be negative.

@Patrick

IC is not less than IL, then why it is negative?

tan(phi) = ((v/xL-v/xc)/v/r).
= IL - IC/IR.
= - 28.44.

Yes, you are right @Rutuja.

The phase difference is <= 90 degrees. It is customary to use the angle by which the voltage leads the current. This leads to a positive phase for inductive circuits since current lags the voltage in an inductive circuit. The phase is negative for a capacitive circuit since the current leads the voltage.

If the inductive reactance is greater than the capacitive reactance, i.e. XL > XC, then the RLC circuit has lagging phase angle and if the capacitive reactance is greater than the inductive reactance, i.e. XC > XL then the RLC circuit has a leading phase angle.

Lagging phase angle (positive phase angle).
Leading phase angle (negative phase angle).