Course Seminar on
“PARALLEL RESONANCE WITH PROBLEM”
Presented by
 Student Name :- Ashish Anil Sadavarti
Course Name: Network Theory (PCCET303T)
Course In-charge: Mohammad Waseem Akram
SB
Jain
Department of Electronics & Telecommunication Engineering

SB
Jain
Department of Electronics & Telecommunication Engineering
Contents
 Introduction
 Impedance In A Parallel Resonance Circuit
 Susceptance At Resonance
 Bandwidth Of A Parallel Resonance Circuit
 Example

SB
Jain
Department of Electronics & Telecommunication Engineering
 Define Parallel Resonance
Parallel resonance is a resonance condition that usually
occurs in parallel resonant circuits, where the voltage
becomes a maximum for a given current. Being a parallel
resonance means the impedance is high and inrush surge
current relatively low compared to a simple capacitor.

SB
Jain
Department of Electronics & Telecommunication Engineering
Parallel resonance occurs when the
supply frequency creates zero phase
difference between the supply voltage
and current producing a resistive circuit

SB
Jain
Department of Electronics & Telecommunication
 Impedance In A Parallel Resonance Circuit
Thus at resonance, the impedance of the parallel
circuit is at its maximum value and equal to the
resistance of the circuit creating a circuit condition
of high resistance and low current.

SB
Jain
Department of Electronics & Telecommunication Engineering
 Susceptance At Resonance
As the total susceptance is zero at
the resonant frequency, the
admittance is at its minimum and
is equal to the conductance, G.
Therefore at resonance the current
flowing through the circuit must
also be at its minimum as the
inductive and capacitive branch
currents are equal ( IL= IC ) and are
180o out of phase.

SB
Jain
Department of Electronics & Telecommunication Engineering
The bandwidth of the parallel resonant response
curve is measured between the half power points.
This corresponds to the 70.7% voltage points since
power is proportional to E2. ((0.707)2 = 0.50) Since
voltage is proportional to impedance, we may use the
impedance curve.
 Bandwidth Of A Parallel Resonance Circuit

SB
Jain
Department of Electronics & Telecommunication Engineering
A parallel resonance network consisting of a resistor of 60Ω, a capacitor of 120uF and
an inductor of 200mH is connected across a sinusoidal supply voltage which has a
constant output of 100 volts at all frequencies. Calculate, the resonant frequency, the
quality factor and the bandwidth of the circuit, the circuit current at resonance and
current magnification.
 Parallel Resonance Example

SB
Jain
Department of Electronics & Telecommunication Engineering
2. Inductive Reactance at Resonance, XL
3. Quality factor, Q
1. Resonant Frequency, ƒr

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Jain
Department of Electronics & Telecommunication Engineering
4. Bandwidth, BW
5. The upper and lower -3dB frequency points, ƒH and ƒL

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Jain
Department of Electronics & Telecommunication Engineering
6. Circuit Current at Resonance, IT
At resonance the dynamic impedance of the circuit is equal to R
7. Current Magnification, Imag

SB
Jain
Department of Electronics & Telecommunication Engineering
 Note that the current drawn from the supply at resonance (the resistive
current) is only 1.67 amps, while the current flowing around the LC tank
circuit is larger at 2.45 amps. We can check this value by calculating the
current flowing through the inductor (or capacitor) at resonance.

SB
Jain
Department of Electronics & Telecommunication Engineering
 Resonant Frequency using Impure Inductor
Where: L is the inductance of the coil, C is the parallel capacitance
and RS is the DC resistive value of the coil.

SB
Jain
Department of Electronics & Telecommunication Engineering