‹#› Eeng 224
Chapter 10 Sinusoidal Steady State Analysis
Chapter Objectives: Apply previously learn circuit techniques to sinusoidal steady-state
analysis.
Learn how to apply nodal and mesh analysis in the frequency domain.
Learn how to apply superposition, Thevenin’s and Norton’s theorems
in the frequency domain. Learn how to analyze AC Op Amp circuits.
Be able to use PSpice to analyze AC circuits.
Apply what is learnt to capacitance multiplier and oscillators.
•
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Steps to Analyze AC Circuits
Transform the circuit to the Phasor Domain.
Solve the problem using circuit techniques listed below
1) Nodal Analysis
2) Mesh Analysis
3) Superposition
4) Source transformation
5) Thevenin or Norton Equivalents
Transform the resulting circuit back to time domain.
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Steps to Analyze AC Circuits
Transform the circuit to the phasor or frequency
domain.
Solve the problem using circuit techniques (nodal
analysis, mesh analysis, superposition, etc.).
Transform the resulting phasor to the time domain.
Time to Freq Solve
Variables in Freq Freq to Time
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Nodal Analysis
Since KCL is valid for phasors, we can analyze AC circuits by
NODAL analysis.
Determine the number of nodes within the network.
Pick a reference node and label each remaining node with a
subscripted value of voltage: V1, V2 and so on.
Apply Kirchhoff’s current law at each node except the reference.
Assume that all unknown currents leave the node for each
application of Kirhhoff’s current law.
Solve the resulting equations for the nodal voltages.
For dependent current sources: Treat each dependent current
source like an independent source when Kirchhoff’s current law
is applied to each defined node. However, once the equations are
established, substitute the equation for the controlling quantity to
ensure that the unknowns are limited solely to the chosen nodal
voltages.
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Nodal Analysis
Practice Problem 10.1: Find v1 and v2 using nodal analysis
Since KCL is valid for phasors, we can analyze AC circuits by
NODAL analysis.
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Nodal Analysis Practice Problem 10.1
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Nodal Analysis Practice Problem 10.1
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Mesh Analysis
Practice Problem 10.4: Calculate the current Io
Meshes 2 and 3 form a
supermesh as shown in
the circuit below.
Since KVL is valid for phasors, we can analyze AC circuits by
MESH analysis.
‹#› Eeng 224
Mesh Analysis Practice Problem 10.4: Calculate the current Io
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Mesh Analysis Practice Problem 10.4: Calculate the current Io
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Superposition Theorem The superposition theorem eliminates the need for solving simultaneous linear
equations by considering the effect on each source independently.
To consider the effects of each source we remove the remaining sources; by setting
the voltage sources to zero (short-circuit representation) and current sources to zero
(open-circuit representation).
The current through, or voltage across, a portion of the network produced by each
source is then added algebraically to find the total solution for current or voltage.
The only variation in applying the superposition theorem to AC networks with
independent sources is that we will be working with impedances and phasors instead of
just resistors and real numbers.
The superposition theorem is not applicable to power effects in AC networks since
we are still dealing with a nonlinear relationship.
It can be applied to networks with sources of different frequencies only if the total
response for each frequency is found independently and the results are expanded in a
nonsinusoidal expression .
One of the most frequent applications of the superposition theorem is to electronic
systems in which the DC and AC analyses are treated separately and the total solution is
the sum of the two.
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Superposition Theorem
When a circuit has sources operating at different
frequencies,
• The separate phasor circuit for each frequency
must be solved independently, and
• The total response is the sum of time-domain
responses of all the individual phasor circuits.
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Superposition Theorem
a) All sources except DC 5-V set to zero b) All sources except 10cos(10t) set to zero
Exp. 10.6 Superposition Technique for sources having different frequencies
Superposition Theorem applies to AC circuits as well.
For sources having different frequencies, the total response must be obtained by
adding individual responses in time domain.
‹#› Eeng 224
c) All sources except 2 sin 5t set to zero
Superposition Theorem
Exp. 10.6 Superposition Technique for sources having different frequencies
vo= v1+ v2+ v3
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Superposition Theorem
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
‹#› Eeng 224
Superposition Theorem
‹#› Eeng 224
Superposition Theorem
P.P.10.6 Superposition Technique for sources having different Frequencies
‹#› Eeng 224
Superposition Theorem
‹#› Eeng 224
Superposition Theorem
Payam zarbakhsh
EElE301 Circuit Theory II
Department of Electrical and Electronic Engineering
Cyprus International university
Top Related