AC2 Fundamentals Unit 3 – Parallel Resonance
UNIT 3 – PARALLEL RESONANCE
UNIT OBJECTIVE
At the completion of this unit, you will be able to analyze parallel resonant LC circuits by using
calculations and measurements.
UNIT FUNDAMENTALS
Resonance occurs in series and parallel circuits. The resonant frequency (fr) of a parallel
resonant circuit is calculated with the same formula used for series resonant circuits.
fr = 1/2π√LC
In a parallel LC circuit, the generator voltage (VGEN) is applied across each component. The
component currents (IC and IL) are determined from the following equations.
IC = VGEN/XC IL = VGEN/XL
The current in the capacitor (IC) leads the generator voltage (VGEN) by 90°. The current in the
inductor (IL) lags the generator voltage by 90°. At resonance, the currents (IC and IL) are equal
and opposite in their effect, so they cancel one another. The total current drawn from the
generator is the line current (IT).