Circuit Analysis

Circuit Analysis (EE-126)
Engr. Dr. Raja Masood Larik
rmlarik@neduet.edu.pk
• Class code: ak3xqba
MEET LINK: https://meet.google.com/lookup/g6rnx4hvb2
• B.E (Electrical Engineering), NED University of Engineering & Technology Karachi, Sindh-Pakistan. 1998.
• M.Engg (Electrical Engineering, CGPA 3.45/4.00), NED University of Engineering& Technology Karachi,
Sindh-Pakistan. 2006
• Doctor of Philosophy (Electrical Engineering) from University Technology Malaysia (UTM). CGPA
3.67/4.00 2019.
• Dr. Larik (Google Scholar Profile)
• https://scholar.google.com/citations?hl=en&user=7z1g_I0AAAAJ
Lecture Notes by Dr.R.M.Larik 1

• Engineering Circuit Analysis by William H. Hayt 8th edition (Text Book)
• Fundamentals of Electric circuits by Charles k Alexander (Reference Book)
• Introduction to Electric Circuits by Dorf, Richard C (Reference Book)
• Electric Circuits by Nilsson, James W (Reference BooK)
• Concepts in Electric circuits by Dr.Wasim Naseem (Reference BooK)
• Electric Circuits by Theodore F.Bogart (Reference BooK)
• Electric Circuits by H.Alex Romanowitz (Reference BooK)

1.Poly Phase Circuits
2.Magnetically Coupled Circuits
3.Two Port Networks
Poly Phase circuits
➢ Balance Three Phase Voltages
➢ Balance Wye Wye Connection
➢ Balanced Wye-Delta Connection
➢ Balanced Delta-Delta Connection
➢ Balanced Delta-Wye Connection
➢ Power in Balanced System
➢ Unbalanced Three Phase Systems

Poly Phase Circuits
Learning Outcomes
▪ Be Familiar with ac single and three phase system
▪ The basics of ac generation from source (Generators/alternator)
▪ The basic difference between balanced and unbalanced three-phase system
▪ To analyse three phase circuits
▪ Connection pattern for three phase i.e. star/delta

AC Generation
Three things must be present in order to produce electrical current:
a) Magnetic field
b) Conductor
c) Relative motion
▪ Conductor cuts lines of magnetic flux, a voltage is induced in the conductor
Direction and Speed are important

What is 1 and 3 Phase?
• 1-Phase (voltage which appears between line to neutral is known as
phase voltage Range from 215-240 V) permissible limit 180V
• Wye or Star Connection
• 3-pahse (Voltage appears between any two lines is known as line
voltage line to line voltage the 3 phase voltage Range from 415-440 V
permissible limit 380V

Single Phase generation

Conductor and magnetic field
have zero degree angle (both
are parallel to each other

Negative Maximum
induced Voltage

No relative motion
between conductor
and magnetic field Lecture Notes by Dr.R.M.Larik 16

Advantages and importance of three-phase systems
An AC generator designed to develop a single sinusoidal voltage for each rotation of the shaft (rotor)
is referred to as a single-phase AC generator.
If the number of coils on the rotor is increased in a specified manner, the result is a Polyphase AC
generator, which develops more power than one AC phase voltage per rotation of the rotor
In general, three-phase systems are preferred over single-phase systems for the transmission of
power for many reasons.
1. The instantaneous power in three-phase system can be constant (not pulsating as in a single phase
circuit).
2. For the same transmitted power, three-phase systems consume less wires.
3. The lighter lines are easier to install, and the supporting structures can be less massive and farther
apart.
4. In general, most larger motors are three phase because they are essentially self starting and do not
require a special design or additional starting circuitry.
For the above reasons, most of the power distribution systems in US and over the world, use three-
phase systems.
The first three-phase electrical system was patented in 1882 by John
Hopkinson - British physicist, electrical engineer, Fellow of the Royal Society.

Three Phase generation

WHY WE STUDY 3 PHASE SYSTEM ?
ALL electric power system in the world used 3-
phase system to
GENERATE, TRANSMIT and DISTRIBUTE
One phase, two phase, can be taken from
three phase system rather than generated
independently

Three Phase generation

Important relation of Impedance

What is Phase? What is Line?
The voltage appears between line to neutral is termed as phase voltage
The voltage appears between any two lines (phases) is Line voltage.
We have commonly two types of connection (to connect windings) either we connect in star or delta pattern.
Both connections have certain advantages as well as disadvantages

What is Balanced and Unbalanced 3 Phase System?
Unbalanced 3 Phase System
Each impedance of all phase are dislike for example the impedances are
(4+j2)ohm ,(6+j3)ohm and (8+j5)ohm (Single Phase loads at homes and
Offices)
Balanced 3 Phase System
Balance 3 Phase System each impedance having same value for
example (3+j3)ohm (3+j3)ohm and (3+j3)ohm (3 Phase Induction motor
used in industry)

Single Phase, two and three wire Circuits
Lecture Notes by Dr.R.M.Larik
Two Phase 3 Wire
system ac sources
operates at different
phases
30

Three Phase 4 wire Circuits

Three Phase Generation
The three-phase generator has three induction coils placed 120° apart on the stator.
• The three coils have an equal number of turns, the voltage induced across each coil will have the
same peak value, shape and frequency. Internal impedance of a generator is usually inductive
(due to the use of coils).

Wye Connected Generator

Delta Connected Generator
The Line voltages are equals to
phase voltages while the line
current equals Under root 3
times phase current
34

Balanced 3 Phase Loads

Balanced 3 Phase Voltages

3 Phase Connections

Wye Connection

Balanced Y-Y Connections
• A balanced Y-Y system, showing the source, line and load impedances.
41

Balanced Wye Wye Connection

Wye –Delta Connection

Delta Delta Connection

Delta-Wye Connection

Circuit Analysis

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