The phenomenon of resonance occurs both in case of parallel and series circuit which is supplied by an alternating ac source. Resonant circuit consists of these components - R , L and C . In the parallel RLC circuit the condition for resonance occurs when the susceptance part is zero.
However admittance Y = G + j B
= 1 / R + j ω C + 1 / j ω L
= 1 / R + j (ωC - 1/ω L)
The frequency at which resonance occurs is ω0 C - 1 / ω0 L = 0
ω0 = 1/ √LC
At resonant frequency current becomes maximum .
A parallel resonating circuit is also called rejector circuit or anti-resosnant circuit. Another common name is tuned circuit .
Properties of resonance of parallel RLC circuit are given below :
- Power factor is unity
- Current at resonance is [V / (L /CR)] and is in phase with applied voltage.The value of current at resonance is minimum.
- Net impedance at parallel circuit is maximum and equal to (L/CR) Ω .
- The admittance is minimum and net susceptance is zero at resonance
- The susceptance frequency of the circuit is given as f0 = 1/ 2π √ (1/ LC - R2 / L2)