Analysis of Parallel Tuned Circuit

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Analysis of Parallel Tuned Circuit

Analysis of Parallel Tuned Circuit- A parallel tuned circuit consists of a capacitor C and inductor L in parallel as shown in Fig-1 (i).

In practice, some resistance R is often present with the coil.

If an alternating voltage is applied across this closed circuit, the frequency of oscillations are that of the applied voltage.

However, if the frequency of applied voltage is adequate to the natural or resonant frequency of LC circuit, then electrical resonance will occur.

Under such conditions, the impedance of the tuned circuit becomes maximum and also the line current is minimum.

The circuit then draws barely enough energy from a.c. supply necessary to beat the losses within the resistance R.

Parallel resonance

A shunt circuit containing reactive elements (L and C ) is *resonant when
the circuit power factor is unity i.e. apply voltage and therefore the supply current are in phase.

The phasor diagram of the closed circuit is show in Fig-1 (ii).

The coil current IL has two rectangular
components viz active component I_L cos φ_L and reactive component I_L sin φ_L.

This loop will
resonate when the circuit power factor is unity.

This is possible only if the web reactive component of the circuit current is zero i.e.

IC − IL sin φL = 0
or IC = IL sin φL
Resonance in shunt circuit will be obtain by changing the availability frequency.

At some frequency f_r
(called resonant frequency), IC = IL sin φL and resonance occurs.
* Resonance means to be in step with. In an a.c. circuit if applied voltage and provide current are in phase
(i.e., in step with), resonance is claimed to occur.
If this happens in an exceedingly parallel a.c. circuit, it's call parallel
resonance.

occurs (i.e. reactive componnent of circuit current becomes zero) is term the resonant frequency f_r .)

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