Electrical Engineering ⇒ Topic : General Case for Parallel Resonance

General Case for Parallel Resonance

We have discussed above parallel resonance for a circuit consisting of a coil (R_L series circuit) in parallel with an ideal capacitor. However, no capacitor is perfect and can be considered to consist of an ideal capacitor in series with a resistor. The circuit then becomes as shown in Fig.(a). The total admittance Y_T of this circuit is given by ;

                                                     figure (a)

Resonance is defined as a circuit condition of unity power factor. Under this condition, the circuit admittance is a pure conductance. In other words, circuit susceptance is zero. Therefore, at resonance, the j part of eq. (i) must be zero i.e