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Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n 102 [email protected] http://scholar.cu.edu.eg/refky/

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Page 1: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals & Phasors

Dr. Mohamed Refky Amin

Electronics and Electrical Communications Engineering Department (EECE)

Cairo University

[email protected]

http://scholar.cu.edu.eg/refky/

Page 2: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

OUTLINE

โ€ข Previously on ELCN102

โ€ข AC Circuits

โ€ข Sinusoidal Signals

โ€ข Phasor Representation

Dr. Mohamed Refky 2

Page 3: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

CapacitorsWhen a voltage source is connected to a capacitor, an electric

field is generated in the dielectric and charges are accumulated on

the plates.

๐‘„ = ๐ถ ร— ๐‘‰

๐ถ =๐‘„

๐‘‰

The amount of charge (๐‘„) that a capacitor can store per volt

across the plates, is its capacitance (๐ถ).

Coulomb Farad

Volt

3

Page 4: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Series and Parallel Combinations

Series Capacitors

1

๐ถ๐‘’๐‘ž=

1

๐ถ1+

1

๐ถ2+โ‹ฏ+

1

๐ถ๐‘

๐‘„ = ๐ถ ร— ๐‘‰

4

Page 5: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Series and Parallel Combinations

Parallel Capacitors ๐‘„ = ๐ถ ร— ๐‘‰

๐ถ๐‘’๐‘ž = ๐ถ1 + ๐ถ2 +โ‹ฏ+ ๐ถ๐‘

5

Page 6: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

InductorsWhen the current flowing through an

inductor changes, the magnetic field induces

a voltage in the conductor, according to

Faradayโ€™s law of electromagnetic induction,

to resist this change in the current.

๐‘ฃ๐ฟ ๐‘ก = ๐ฟ๐‘‘๐‘–๐ฟ ๐‘ก

๐‘‘๐‘ก

๐ฟ is the inductance in Henri (๐ป)

6

Page 7: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Series and Parallel Combinations

Series Inductors

๐ฟ๐‘’๐‘ž = ๐ฟ1 + ๐ฟ2 +โ‹ฏ+ ๐ฟ๐‘

7

Page 8: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Series and Parallel Combinations

Parallel Inductors

1

๐ฟ๐‘’๐‘ž=

1

๐ฟ1+

1

๐ฟ2+โ‹ฏ+

1

๐ฟ๐‘

8

Page 9: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Transient AnalysisThe transient response of the circuit is the response when the input

is change suddenly or a switches status change.

๐‘ฃ ๐‘ก =

๐‘ฃ1 ๐‘ก , ๐‘ก0 < ๐‘ก < ๐‘ก1๐‘ฃ2 ๐‘ก , ๐‘ก1 < ๐‘ก < ๐‘ก2

โ‹ฎ๐‘ฃ๐‘› ๐‘ก , ๐‘ก๐‘›โˆ’1 < ๐‘ก < ๐‘ก๐‘›

๐‘ฃ ๐‘ก the same

9

Page 10: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Steady State AnalysisThe steady state response of the circuit is the response when the

status of the circuit does not change for long time.

๐‘ฃ ๐‘ก the same

10

Page 11: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Time Domain Analysis 1st Order Systems

๐‘‰๐‘– and ๐‘‰๐‘“ are the initial and final capacitor voltages, respectively.

๐œ = ๐‘…๐‘’๐‘ž๐ถ, ๐‘…๐‘’๐‘ž is the resistance seen between the capacitor nodes

while all sources are switched off.

๐‘ฃ๐‘ ๐‘ก = ๐‘‰๐‘“ โˆ’ ๐‘‰๐‘“ โˆ’ ๐‘‰๐‘– ๐‘’โˆ’๐‘ก๐œ

RC Circuits

11

Page 12: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

Time Domain Analysis 1st Order Systems

๐ผ๐‘– and ๐ผ๐‘“ are the initial and final inductor current, respectively.

๐œ = ๐ฟ/๐‘…๐‘’๐‘ž, ๐‘…๐‘’๐‘ž is the resistance seen between the inductor nodes

while all sources are switched off.

๐‘–๐ฟ ๐‘ก = ๐ผ๐‘“ โˆ’ ๐ผ๐‘“ โˆ’ ๐ผ๐‘– ๐‘’โˆ’๐‘ก๐œ

RL Circuits

12

Page 13: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

AC CircuitsAn AC circuit is a combination of active elements (Voltage and

current sources) and passive elements (resistors, capacitors and

coils).

Unlike resistance, capacitors and coils can store energy and do

not dissipate it. Thus, capacitors and coils are called storage

elements.13

Page 14: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Previously on ELCN102

Dr. Mohamed Refky

AC CircuitsAn AC circuit is a combination of active elements (Voltage and

current sources) and passive elements (resistors, capacitors and

coils).

The sources are usually AC sinusoidal voltage or current sources

14

Page 15: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

DefinitionA sinusoid is a signal that has the form of the sine or cosine

function.

๐‘‰๐ด๐ถ = ๐‘‰๐‘š sin ๐œ”๐‘ก ๐œ”๐‘‡ = 2๐œ‹ โ†’ ๐œ” =2๐œ‹

๐‘‡

amplitude

15

Page 16: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

DefinitionA sinusoid is a signal that has the form of the sine or cosine

function.

โ€ข ๐‘‰๐‘š is the amplitude of the sinusoid

โ€ข ๐œ” is the angular frequency in rad/s

โ€ข ๐œ”๐‘ก is the argument of the sinusoid

โ€ข ๐‘“ =๐œ”

2๐œ‹is the sinusoid frequency

โ€ข ๐‘‡ =1

๐‘“is the sinusoid period

๐‘‰๐ด๐ถ = ๐‘‰๐‘š sin ๐œ”๐‘ก ๐œ”๐‘‡ = 2๐œ‹ โ†’ ๐œ” =2๐œ‹

๐‘‡

16

Page 17: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Why Do We Study Sinusoidal Signals?We study the sinusoid because:

โ€ข A sinusoidal signal is easy to generate and transmit. It is the

form of voltage generated throughout the world and supplied

to homes, factories, laboratories.

โ€ข Through Fourier analysis, any practical periodic signal can be

represented by a sum of sinusoids.

โ€ข A sinusoid is easy to handle mathematically. The derivative

and integral of a sinusoid are themselves sinusoids.

โ€ข For a linear time invariant system (LTI), a sinusoid is an eigen

function to the system.

17

Page 18: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Eigen function of an LTI system

If ๐‘ฅ ๐‘ก is an Eigen function to an LTI system, the response of the

system to the input ๐‘ฅ ๐‘ก is

๐‘ฆ ๐‘ก = ๐›ผ๐‘ฅ ๐‘ก

๐›ผ is generally complex number causing a change in both the

magnitude and phase.

18

Page 19: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Phase shift

๐‘‰๐ด๐ถ = ๐‘‰๐‘š sin ๐œ”๐‘ก๐‘‰๐ด๐ถ = ๐‘‰๐‘š sin ๐œ”๐‘ก + ๐œ™๐‘‰๐ด๐ถ = ๐‘‰๐‘š sin ๐œ”๐‘ก โˆ’ ๐œ™

The phase shift is positive if the signal is shifted to the left and isnegative if the signal is shifted to the right.

19

Page 20: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Complex NumbersA complex number can be written in two forms: rectangular

form and polar form.

The rectangular form consists of a

real part and an imaginary part.

๐‘ = ๐‘ฅ + ๐‘—๐‘ฆ

The polar form consists of a

magnitude and phase.

๐‘ = ๐‘Ÿ๐‘’๐‘—๐œƒ = ๐‘Ÿโˆ ๐œƒ

20

Page 21: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Complex NumbersA complex number can be written in two forms: rectangular

form and polar form.

To convert from rectangular form

to polar form

๐‘Ÿ = ๐‘ฅ2 + ๐‘ฆ2,

To convert from polar form to

rectangular form

๐‘ฅ = ๐‘Ÿ cos ๐œƒ , ๐‘ฆ = ๐‘Ÿ sin ๐œƒ

๐œƒ = tanโˆ’1๐‘ฆ

๐‘ฅ

21

Page 22: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Complex NumbersA complex number can be written in two forms: rectangular

form and polar form.

Complex numbers are added/subtracted easily in rectangular

form

๐‘1 = ๐‘ฅ1 + ๐‘—๐‘ฆ1, ๐‘2 = ๐‘ฅ2 + ๐‘—๐‘ฆ2

Then

๐‘1 + ๐‘2 = ๐‘ฅ1 + ๐‘ฅ2 + ๐‘— ๐‘ฆ1 + ๐‘ฆ2

๐‘1 โˆ’ ๐‘2 = ๐‘ฅ1 โˆ’ ๐‘ฅ2 + ๐‘— ๐‘ฆ1 โˆ’ ๐‘ฆ2

22

Page 23: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Sinusoidal Signals

Dr. Mohamed Refky

Complex NumbersA complex number can be written in two forms: rectangular

form and polar form.

Complex numbers are multiplied/divided easily in polar form

๐‘1 = ๐‘Ÿ1๐‘’๐‘—๐œƒ1 = ๐‘Ÿ1โˆ ๐œƒ1, ๐‘2 = ๐‘Ÿ2๐‘’

๐‘—๐œƒ2 = ๐‘Ÿ2โˆ ๐œƒ2

Then

๐‘1 ร— ๐‘2 = ๐‘Ÿ1 ร— ๐‘Ÿ2 ๐‘’๐‘— ๐œƒ1+๐œƒ2 = ๐‘Ÿ1 ร— ๐‘Ÿ2 โˆ  ๐œƒ1 + ๐œƒ2

๐‘1/๐‘2 = ๐‘Ÿ1/๐‘Ÿ2 ๐‘’๐‘— ๐œƒ1โˆ’๐œƒ2 = ๐‘Ÿ1/๐‘Ÿ2 โˆ  ๐œƒ1 โˆ’ ๐œƒ2

23

Page 24: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Definition

The locus of ๐‘’๐‘—๐œƒ is a circle with radius 1.

๐‘’๐‘—๐œƒ

๐œƒ = 0๐‘œ๐œƒ = 30๐‘œ๐œƒ = 60๐‘œ๐œƒ = 135๐‘œ๐œƒ = 225๐‘œ๐œƒ = 315๐‘œ ๐œƒ = โˆ’45๐‘œ

24

Page 25: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Definition

sin ๐œƒ

๐‘’๐‘—๐œƒ = cos ๐œƒ + ๐‘— sin ๐œƒ

cos ๐œƒ = ๐‘…๐‘’ ๐‘’๐‘—๐œƒ

sin ๐œƒ = ๐ผ๐‘š ๐‘’๐‘—๐œƒ

Eulerโ€™s identity

cos ๐œƒ

๐‘’๐‘—๐œƒ

25

Page 26: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

DefinitionThe sinusoid function ๐‘ฃ ๐‘ก = ๐‘‰๐‘š cos ๐œ”๐‘ก + ๐œ™ can be written as

๐‘ฃ ๐‘ก = ๐‘…๐‘’ ๐‘‰๐‘š๐‘’๐‘— ๐œ”๐‘ก+๐œ™

= ๐‘…๐‘’ ๐‘‰๐‘š๐‘’๐‘— ๐œ™ ๐‘’๐‘— ๐œ”๐‘ก

= ๐‘…๐‘’ ๐‘‰๐‘’๐‘— ๐œ”๐‘ก

๐‘‰ = ๐‘‰๐‘š๐‘’๐‘— ๐œ™ = ๐‘‰๐‘šโˆ ๐œ™

๐‘‰๐‘š๐‘’๐‘— ๐œ™ is the phasor representation of ๐‘‰๐‘š cos ๐œ”๐‘ก + ๐œ™

26

Page 27: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

DefinitionA sinusoid

๐‘ฃ ๐‘ก = ๐‘‰๐‘š cos ๐œ”๐‘ก + ๐œ™

= ๐‘…๐‘’ ( ๐‘‰๐‘’๐‘—๐œ”๐‘ก)

can be represented by the projection,

on the horizontal axis, of a phasor

rotating with a constant angular

velocity ๐œ”.

๐‘‰ = ๐‘‰๐‘šโˆ ๐œ™

๐‘‰๐‘š is the circle radius

โˆ ๐œ™ is the initial phasor position27

Page 28: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

DefinitionA sinusoid

๐‘ฃ ๐‘ก = ๐‘‰๐‘š sin ๐œ”๐‘ก + ๐œ™

= ๐ผ๐‘š ( ๐‘‰๐‘’๐‘—๐œ”๐‘ก)

can be represented by the projection, on the vertical axis, of a

phasor rotating with a constant angular velocity ๐œ”.

28

Page 29: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasors

The cosine function leads the sine function by 90๐‘œ

cos ๐œ”๐‘ก = sin ๐œ”๐‘ก + 90๐‘œ

sin ๐œ”๐‘ก = cos ๐œ”๐‘ก โˆ’ 90๐‘œ

29

Page 30: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Graphical approachThe cosine function leads the sinefunction by 90๐‘œ

cos ๐œ”๐‘ก = sin ๐œ”๐‘ก + 90๐‘œ

sin ๐œ”๐‘ก = cos ๐œ”๐‘ก โˆ’ 90๐‘œ

Graphical approach is very handyin representing the addition oftwo sinusoids of the samefrequency

๐‘‰ = ๐›ผ cos ๐œ”๐‘ก + ๐›ฝ sin ๐œ”๐‘ก

= ๐›พ cos ๐œ”๐‘ก โˆ’ ๐œƒ ๐›พ = ๐›ผ2 + ๐›ฝ2, ๐œƒ = tanโˆ’1๐›ฝ

๐›ผ30

Page 31: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Sinusoid-Phasors transformation

Phasor domain is also known as the frequency domain.

Time-domain representation Phasor representation

๐‘‰๐‘š cos ๐œ”๐‘ก + ๐œ™ ๐‘‰๐‘šโˆ ๐œ™

๐‘‰๐‘š sin ๐œ”๐‘ก + ๐œ™ ๐‘‰๐‘šโˆ ๐œ™ โˆ’ 90๐‘œ

๐ผ๐‘š cos ๐œ”๐‘ก + ๐œƒ ๐ผ๐‘šโˆ ๐œƒ

๐ผ๐‘š sin ๐œ”๐‘ก + ๐œƒ ๐ผ๐‘šโˆ ๐œƒ โˆ’ 90๐‘œ

31

Page 32: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (1)For the sinusoid 5sin(4๐œ‹๐‘ก + 60๐‘œ) calculate its amplitude, phase,

angular frequency, frequency, and period.

32

Page 33: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (2)Transform these sinusoids to phasors representation:

๐‘ฃ = 6cos(50๐‘ก โˆ’ 40๐‘œ)

๐‘– = โˆ’4 sin(50 ๐‘ก + 50๐‘œ)

33

Page 34: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (3)Transform these phasors representation to sinusoids:

๐‘‰ = 8๐‘’โˆ’๐‘—20๐‘œ

๐‘– = 3 + ๐‘—4

34

Page 35: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (4)Calculate the phase angle (phase difference) between:

๐‘ฃ1 = โˆ’10cos(๐œ”๐‘ก + 50๐‘œ) ๐‘Ž๐‘›๐‘‘ ๐‘ฃ2 = 12 sin(๐œ”๐‘ก โˆ’ 10๐‘œ)

State which sinusoid is leading.

35

Page 36: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

If the current in a resistor ๐‘… is given by:

๐‘–๐‘… ๐‘ก = ๐ผ๐‘šcos(๐œ”๐‘ก)

The resistor voltage will be given by

๐‘ฃ๐‘… ๐‘ก = ๐‘… ร— ๐‘–๐‘… ๐‘ก = ๐‘…๐ผ๐‘š cos ๐œ”๐‘ก = ๐‘‰๐‘šcos(๐œ”๐‘ก)

๐ผ = ๐ผ๐‘šโˆ 0๐‘œ ๐‘‰ = ๐‘‰๐‘šโˆ 0

๐‘œ = ๐‘…๐ผ๐‘šโˆ 0๐‘œ

Resistor

For a resistor, the voltage and current are in phase

36

Page 37: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

If the current in an inductor ๐ฟ is given by:

๐‘–๐ฟ ๐‘ก = ๐ผ๐ฟcos(๐œ”๐‘ก)

The inductor voltage will be given by

๐‘ฃ๐ฟ ๐‘ก = ๐ฟ๐‘‘๐‘–๐ฟ ๐‘ก

๐‘‘๐‘ก= โˆ’๐œ”๐ฟ๐ผ๐ฟ sin ๐œ”๐‘ก = โˆ’๐‘‰๐ฟ sin(๐œ”๐‘ก)

๐ผ = ๐ผ๐‘šโˆ 0๐‘œ ๐‘‰ = ๐‘‰๐ฟโˆ 90

๐‘œ = ๐œ”๐ฟ๐ผ๐ฟโˆ 90๐‘œ

Inductor

For an inductor, the current lags the voltage by 90๐‘œ

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Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

If the voltage in a capacitor ๐ถ is given by:

๐‘ฃ๐ถ ๐‘ก = ๐‘‰๐ถcos(๐œ”๐‘ก)

The capacitor current will be given by

๐‘–๐ถ ๐‘ก = ๐ถ๐‘‘๐‘ฃ๐ถ ๐‘ก

๐‘‘๐‘ก= โˆ’๐œ”๐ถ๐‘‰๐ถ sin ๐œ”๐‘ก = โˆ’๐ผ๐ถ sin(๐œ”๐‘ก)

๐‘‰ = ๐‘‰๐ถโˆ 0๐‘œ ๐ผ = ๐ผ๐ถโˆ 90

๐‘œ = ๐œ”๐ถ๐‘‰๐ถโˆ 90๐‘œ

Capacitor

For an capacitor, the current leads the voltage by 90๐‘œ

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Page 39: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

๐ผ = ๐ผ๐‘šโˆ 0๐‘œ ๐‘‰ = ๐‘…๐ผ๐‘šโˆ 0

๐‘œ

๐‘‰ = ๐‘‰๐‘šโˆ 0๐‘œ ๐ผ = ๐ถ๐œ”๐‘‰๐‘šโˆ 90

๐‘œ๐ผ = ๐ผ๐‘šโˆ 0๐‘œ ๐‘‰ = ๐ฟ๐œ”๐ผ๐‘šโˆ 90

๐‘œ

inductor capacitor

resistor

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Page 40: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

The impedance ๐‘ of a circuit is the ratio of the phasor voltage ๐‘‰to the phasor current ๐ผ, measured in ฮฉ.

Resistor Inductor Capacitor

๐‘ฃ๐‘… ๐‘ก = ๐‘…๐‘–๐‘… ๐‘ก ๐‘ฃ๐ฟ ๐‘ก = ๐ฟ๐‘‘๐‘–๐ฟ ๐‘ก

๐‘‘๐‘ก๐‘–๐ถ ๐‘ก = ๐ถ

๐‘‘๐‘ฃ๐ถ ๐‘ก

๐‘‘๐‘ก

๐‘‰๐‘… = ๐‘… ร— ๐ผ๐‘…๐‘‰๐ฟ = ๐œ”๐ฟ๐ผ๐ฟโˆ 90

๐‘œ

= ๐‘—๐ฟ๐œ” ร— ๐ผ๐ฟ

๐ผ๐ถ = ๐œ”๐ถ๐‘‰๐ถโˆ 90๐‘œ

= ๐‘—๐œ”๐ถ ร— ๐‘‰๐ถ

๐‘๐‘… = ๐‘… ๐‘๐ฟ = ๐‘—๐œ”L ๐‘๐ถ =1

๐‘—๐œ”๐ถ= โˆ’

๐‘—

๐œ”๐ถ

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Page 41: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Phasor Relationships for Circuit Elements

The admittance ๐‘Œ of a circuit is the ratio of the phasor current ๐ผto the phasor voltage ๐‘‰, measured in ฮฉโˆ’1.

Resistor Inductor Capacitor

๐‘ฃ๐‘… ๐‘ก = ๐‘…๐‘–๐‘… ๐‘ก ๐‘ฃ๐ฟ ๐‘ก = ๐ฟ๐‘‘๐‘–๐ฟ ๐‘ก

๐‘‘๐‘ก๐‘–๐ถ ๐‘ก = ๐ถ

๐‘‘๐‘ฃ๐ถ ๐‘ก

๐‘‘๐‘ก

๐‘‰๐‘… = ๐‘… ร— ๐ผ๐‘…๐‘‰๐ฟ = ๐œ”๐ฟ๐ผ๐ฟโˆ 90

๐‘œ

= ๐‘—๐ฟ๐œ” ร— ๐ผ๐ฟ

๐ผ๐ถ = ๐œ”๐ถ๐‘‰๐ถโˆ 90๐‘œ

= ๐‘—๐œ”๐ถ ร— ๐‘‰๐ถ

๐‘Œ๐‘… =1

๐‘…๐‘Œ๐ฟ =

1

๐‘—๐œ”L= โˆ’

๐‘—

๐œ”L๐‘Œ๐ถ = ๐‘—๐œ”๐ถ

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Page 42: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Impedance and Admittance

The impedance ๐‘ of a circuit is the ratio of the phasor voltage ๐‘‰to the phasor current ๐ผ, measured in ฮฉ.

๐‘ = ๐‘… + ๐‘—๐‘‹

๐‘… is the resistance & ๐‘‹ is the reactance

๐‘ is inductive if ๐‘‹ is +๐‘ฃ๐‘’.

๐‘ is capacitive if ๐‘‹ is โˆ’๐‘ฃ๐‘’.

๐‘, ๐‘…, and ๐‘‹ are in units of ฮฉ

Impedance

๐‘๐ฟ = ๐‘—๐œ”L

๐‘๐ถ =1

๐‘—๐œ”๐ถ= โˆ’

๐‘—

๐œ”๐ถ

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Page 43: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Impedance and Admittance

The admittance ๐‘Œ of a circuit is the ratio of the phasor current ๐ผ to

the phasor voltage ๐‘‰, measured in ฮฉโˆ’1.

๐‘Œ = ๐บ + ๐‘—๐ต

๐บ is the conductance & ๐ต is the susceptance.

๐‘Œ is inductive if ๐ต is โˆ’๐‘ฃ๐‘’.

๐‘Œ is capacitive if ๐ต is +๐‘ฃ๐‘’.

๐‘Œ, ๐บ, and ๐ต are in units of ฮฉโˆ’1

Admittance

๐‘Œ๐ฟ =1

๐‘—๐œ”L= โˆ’

๐‘—

๐œ”L

๐‘Œ๐ถ = ๐‘—๐œ”๐ถ

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Page 44: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Impedance Combination

๐‘‰๐‘’๐‘ž = ๐‘‰1 + ๐‘‰2 +โ‹ฏ+ ๐‘‰๐‘

๐ผ ร— ๐‘๐‘’๐‘ž = ๐ผ ร— ๐‘1 + ๐ผ ร— ๐‘2 +โ‹ฏ+ ๐ผ ร— ๐‘๐‘

๐‘๐‘’๐‘ž = ๐‘1 + ๐‘2 +โ‹ฏ+ ๐‘๐‘

Series Combination

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Phasor Representation

Dr. Mohamed Refky

Impedance Combination

๐ผ๐‘’๐‘ž = ๐ผ1 + ๐ผ2 +โ‹ฏ+ ๐ผ๐‘

๐‘‰

๐‘๐‘’๐‘ž=

๐‘‰

๐‘1+๐‘‰

๐‘2+โ‹ฏ+

๐‘‰

๐‘๐‘

Parallel Combination

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Page 46: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Impedance Combination

1

๐‘๐‘’๐‘ž=

1

๐‘1+

1

๐‘2+โ‹ฏ+

1

๐‘๐‘

Parallel Combination

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Page 47: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Admittance Combination

๐‘‰๐‘’๐‘ž = ๐‘‰1 + ๐‘‰2 +โ‹ฏ+ ๐‘‰๐‘

๐ผ

๐‘Œ๐‘’๐‘ž=

๐ผ

๐‘Œ1+

๐ผ

๐‘Œ2+โ‹ฏ+

๐ผ

๐‘Œ๐‘

Series Combination

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Page 48: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Admittance Combination

1

๐‘Œ๐‘’๐‘ž=

1

๐‘Œ1+1

๐‘Œ2+โ‹ฏ+

1

๐‘Œ๐‘

Series Combination

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Page 49: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Admittance Combination

๐ผ๐‘’๐‘ž = ๐ผ1 + ๐ผ2 +โ‹ฏ+ ๐ผ๐‘

๐‘‰ ร— ๐‘Œ๐‘’๐‘ž = ๐‘‰ ร— ๐‘Œ1 + ๐‘‰ ร— ๐‘Œ2 +โ‹ฏ+ ๐‘‰ ร— ๐‘Œ๐‘

๐‘Œ๐‘’๐‘ž = ๐‘Œ1 + ๐‘Œ2 +โ‹ฏ+ ๐‘Œ๐‘

Parallel Combination

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Phasor Representation

Dr. Mohamed Refky

Voltage DividerWhen impedances are connected in series, the total voltage

across these impedances is divided between them with a ratio that

depends on the values of theses impedance.

๐‘‰๐‘Ž๐‘ = ๐ผ ร— ๐‘1 + ๐ผ ร— ๐‘2

= ๐ผ ๐‘1 + ๐‘2

๐ผ =๐‘‰๐‘Ž๐‘

๐‘1 + ๐‘2

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Phasor Representation

Dr. Mohamed Refky

Voltage DividerWhen impedances are connected in series, the total voltage

across these impedances is divided between them with a ratio that

depends on the values of theses impedance.

๐‘‰๐‘1 = ๐ผ ร— ๐‘1 = ๐‘‰๐‘Ž๐‘๐‘1

๐‘1 + ๐‘2= ๐‘‰๐‘Ž๐‘

๐‘1๐‘๐‘’๐‘ž

๐‘‰๐‘2 = ๐ผ ร— ๐‘2 = ๐‘‰๐‘Ž๐‘๐‘2

๐‘1 + ๐‘2= ๐‘‰๐‘Ž๐‘

๐‘2๐‘๐‘’๐‘ž

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Phasor Representation

Dr. Mohamed Refky

Current DividerWhen impedances are connected in parallel, the total current is

divide between these impedances with a ratio that depends on the

values of theses impedances.

๐ผ = ๐ผ1 + ๐ผ2 =๐‘‰

๐‘1+๐‘‰

๐‘2

= ๐‘‰๐‘1 + ๐‘2๐‘1๐‘2

๐‘‰ = ๐ผ๐‘1๐‘2

๐‘1 + ๐‘2

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Page 53: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Current DividerWhen impedances are connected in parallel, the total current is

divide between these impedances with a ratio that depends on the

values of theses impedances.

๐ผ1 =๐‘‰

๐‘1= ๐ผ

๐‘2๐‘1 + ๐‘2

= ๐ผ๐‘๐‘’๐‘ž๐‘1

๐ผ2 =๐ผ

๐‘2= ๐ผ

๐‘1๐‘1 + ๐‘2

= ๐ผ๐‘๐‘’๐‘ž๐‘2

๐‘๐‘’๐‘ž =๐‘1๐‘2

๐‘1 + ๐‘253

Page 54: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Star-Delta Transformation

๐‘๐ด๐ต = ๐‘๐ด + ๐‘๐ต +๐‘๐ด๐‘๐ต๐‘๐ถ

๐‘๐ด๐ถ = ๐‘๐ด + ๐‘๐ถ +๐‘๐ด๐‘๐ถ๐‘๐ต

๐‘๐ต๐ถ = ๐‘๐ต + ๐‘๐ถ +๐‘๐ต๐‘๐ถ๐‘๐ด

๐‘๐ด =๐‘๐ด๐ต๐‘๐ด๐ถ

๐‘๐ด๐ถ + ๐‘๐ต๐ถ + ๐‘๐ด๐ต๐‘๐ถ =

๐‘๐ต๐ถ๐‘๐ด๐ถ๐‘๐ด๐ถ + ๐‘๐ต๐ถ + ๐‘๐ด๐ต

๐‘๐ต =๐‘๐ด๐ต๐‘๐ต๐ถ

๐‘๐ด๐ถ + ๐‘๐ต๐ถ + ๐‘๐ด๐ต

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Page 55: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (5)Find the equivalent impedance of the shown circuit. Assume ๐œ”= 50 ๐‘Ÿ๐‘Ž๐‘‘/๐‘ .

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Page 56: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (6)Find the current ๐ผ for the circuit shown

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Page 57: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (7)Find the current ๐ผ for the circuit shown

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Phasor Representation

Dr. Mohamed Refky

Example (8)For the circuit shown,

๐‘… = 5๐‘˜ฮฉ, ๐ถ = 0.1๐œ‡๐น and ๐‘ฃ๐‘Ž๐‘ ๐‘ก = 10 cos(4000๐‘ก)find the circuit current ๐‘– ๐‘ก and the capacitor voltage ๐‘ฃ๐‘ ๐‘ก .

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Page 59: Sinusoidal Signals & Phasors Sinusoidal Signals & Phasors Dr. Mohamed Refky Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com

Phasor Representation

Dr. Mohamed Refky

Example (9)For the circuit shown,

๐‘… = 4ฮฉ, ๐ฟ = 0.2๐ป and ๐‘ฃ๐‘Ž๐‘ ๐‘ก = 5 ๐‘ ๐‘–๐‘›(10๐‘ก)find the circuit current and the inductor voltage.

59