RLC series resonant (also known as series resonant withstand voltage device) circuit is a series connection of pure resistors, pure inductors, and pure capacitors, forming a resonant circuit through this series connection. At the resonant frequency, the phase angle will be zero, and the total impedance of the circuit will be equal to the resistance of the resistors in the circuit. Due to the series connection of these three components, the current through each component will be equal to the current through the entire circuit.

The angular frequency of the circuit can be determined by

The resonance condition of an RLC circuit is X L=X C, where X is the reactance of the inductor and X Ç is the reactance of the capacitor. The reactance of the inductor is given by the following equation: X L=X C, where L is the inductor and c is the capacitor. The reactance of the capacitor is given by the following equation

At resonance Z=R, where z is the impedance of the circuit and R is the resistance, the impedance of the circuit is given by the following equation

At resonance, the phase is

The behavior of the RLC series resonant circuit can be represented by a phasor diagram

The instantaneous voltage through a resistor will be in phase with the current, but the instantaneous voltage through a capacitor (V C) will lag 90 degrees behind the current, while the instantaneous voltage through an inductor (V L) will cause the current to lag 90 degrees. If V L<V C forms an inductive circuit, and if V C>V L forms a capacitive circuit.