Kuwait University College of Engineering & Petroleum Electrical Engineering Department Designed & Edited By Eng. Ahmed Shafik Eng. Mohamed Tawfik Supervised By Dr. Meshaal Al-Shaher Dr. Mona Al-Basman
Kuwait University
College of Engineering & Petroleum
Electrical Engineering Department
Designed & Edited By
Eng. Ahmed Shafik Eng. Mohamed Tawfik
Supervised By
Dr. Meshaal Al-Shaher Dr. Mona Al-Basman
Lab Schedule
Date Experiment Title Quiz Pre-Lab Report
From To
19-Feb 23-Feb DC Spice + AC Spice
26-Feb 2-Mar عطلة العيد الوطني
5-Mar 9-Mar Ex1. Ohm's Law Exp 1 12-Mar 16-Mar Ex2. KVL and KCL Quiz 1 Exp 2 Exp 1 19-Mar 23-Mar Ex3. Node, Mesh and Superposition Quiz 2 Exp 3 Exp 2 26-Mar 30-Mar Ex4. Thevenin Equivalent Theorem + Training Quiz 3 Exp 4 Exp 3
2-Apr 6-Apr DC Practical Exam + DC PSpice test Exp 4
9-Apr 13-Apr Ex5. AC Measurements Exp 5 16-Apr 20-Apr عطلة االسراء والمعراج 23-Apr 27-Apr Ex7. Phase shift Measurements Quiz 4 Exp 7 Exp 5 30-Apr 4-May Exp 8 : Steady-state power calculation Quiz 5 Exp 8 Exp 7
7-May 11-May Ex9. Electric Wiring + Training Quiz 6 Exp 8
14-May 18-May AC Practical Exam + AC PSpice test Exp 9 21-May 23-May اخر تاريخ لمراجعة الدرجات
Grading Policy
Pre-Lab 10%
Reports 10%
5 Quizzes 20%
2 Exams 40%
2 Spice tests 20%
Total 100%
Report Grading
PolicyCover
1
Table of Contents
Objective
Equipment
Theory 1
Procedure + Circuit 1
Pspice simulation 1
Data Sheet
Exercise 4
Conclusion 1 References
Report Format 1
Total 10
Second Midterm is considered as Final Exam
Absence of any practical exam = FA
Absence
o 1st absence = انذار اول
o 2nd
absence = انذار ثاني
o 3rd
absence = FA.
All reports and data sheets should be done by computer; no
hand writing will be accepted.
Pre-Lab = Data Sheet + Spice Simulation
Data Sheet should be signed by the lab engineer at the end of
the lab
Mobiles and Calculators are not allowed in the practical
exams. Any violation of this rule will be considered as
cheating and will be dealt with accordingly.
Lab Regulations
1) Performance & Pre Lab: (10 points)
PSpice simulation report (student name and ID must be typed on the circuit
simulation, otherwise the report will not be graded.) (5 pts)
For the Data Sheet, Theoretical part should be filled in and printed by
computer before the lab. (2 pts)
Note: Lab engineer has to sign the pre lab note before students leave the lab.
Performance: (3 pts)
o Student must attend all Lab sessions in time.
o Students must leave the bench clean and switch all the equipments off
before leaving the lab.
o Food and drinks are not allowed in the labs.
o Cell phone use in the labs is prohibited.
2 grades of the per-lab grade will be deducted if the student violates any of
the previous points.
2) Attendance
Students should attend the lab in time. Late students will not be allowed to
attend the lab and will get zero mark for (Pre Lab Note, Performance, Quiz
and Report).
Students can attend in their section only, for critical cases only, the student
has to download and fill the form and sign it to attend in different section.
Absent students for 3 out of 10 labs or more will get FA.
Absence of any practical tests = FA
3) Report Layout:
A typical lab report should contain the following sections (in order), you can
download the report sample from the site:
Cover Page
Table of Contents
Objective
Theory
Experimental Procedure + Exercise
PSpice Simulation
Data Sheet
Conclusion
References
. Writing techniques:
Report and Pre Lab note should be written by computer.
The font and size of the normal text is TimesNewRoman 12.
The font and size of the heading and subheading is TimesNewRoman 16/14.
The report should contain page numbers.
All figures and tables should have a title caption.
The theory part should contain (figures, equations, description) for each part of
the objective.
1
To be familiar with the laboratory equipment and components.
Verification of Ohm’s law.
Series and parallel circuits.
Part I : Lab equipment and components:
DC Power Supply:
It is a multi-channels power source device to generate a variable DC voltage,
Figure 1-1: DC power supply sample
Function Generator (FG):
It is a device to generate a variable AC signals with different wave forms (sine, square and triangle).
Figure 1-2: Function Generator
Familiarization, and Ohm's Law
Objectives
Theory
1
2
Resistor:
There are two types of resistors in the lab, resistor substitution box (from 0 to 9.999 M) and
discrete resistors. See Figure 1-5 for the discrete resistor values reading table.
Resistor Substitution Box
Discrete Resistors
Figure 1-3: Resistors
4-band Color Code
Figure 1-4: 4-band color code table
4
Example:
(a)
(b)
Figure 1-6: Color code example
a) For the resistor of figure 1-6-a, the value can be calculated as follows:
1 2 3 4R N N N N
Where:
Ni = band value.
R = 02 x 105 + 10% = 200 K + 10%
b) For the resistor of figure 1-6-b, the value can be calculated as follows:
1 2 3 4 5R N N N N N
Where:
Ni = band value.
R = 330 x 101 + 0.1% = 3.3 K + 0.1%
5
Inductor:
There is inductance substitution box in the lab (from 0 to 9.999 H).
Figure 1-7: Inductance substitution box
Capacitor:
There is capacitance substitution box in the lab (from 0 to 99.999 uF).
Figure 1-8: Capacitance substitution box
Digital Multi-Meter (DMM):
DMM is a measuring instrument to measure voltage, current, ohm, frequency.
Figure 1-9: DMM sample
6
Digital Oscilloscope (CRO):
CRO is a multi-channels measuring instrument to measure and display voltage wave forms with
different measurements readings.
Figure 1-10: CRO Sample
Bread Board:
It is a board to connect the circuits.
Figure 1-11: Bread Board Sample
7
Part II : Ohms's Law:
Ohm's Law says: The current in a circuit is directly proportional to the applied voltage.
V I R (1)
Circuit Diagram
Relationship Between V & I (slope=1/R)
Figure 1-12: Ohm’s Law
Part III : Series & Parallel Circuits:
Figure 1-13: Series and Parallel Connections
I
1/R
I
V
8
Connect the circuit as shown in Figure 1-14 by the following steps:
Part I:
Figure 1-14: Circuit Diagram
1) Start Orcad [Appendix A-1]
2) Add a Resistor [Appendix A-2] (R1=4 KΩ)
3) Add DC Voltage Source (Vs) [Appendix A-5]
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Add CRO current probe to measure I [Appendix A-12]
7) Select DC sweep analysis with the following parameters [Appendix A-14]
Name = Vs
Start Value = 0
End Value = 12
Increment = 1
8) Simulate the circuit [Appendix A-13]
9) The following wave form will be displayed in a new window.
10) Calculate the line slope = and compare it with the theoretical value.
V_Vs
0V 0.5V 1.0V 1.5V 2.0V 2.5V 3.0V 3.5V 4.0V 4.5V 5.0V 5.5V 6.0V 6.5V 7.0V 7.5V 8.0V 8.5V 9.0V 9.5V 10.0V
I(R1)
0A
0.4mA
0.8mA
1.2mA
1.6mA
2.0mA
2.4mA
2.8mA
OrCAD Simulation
9
Part II:
1) Start OrCAD [Appendix A-1]
2) Add Resistors [Appendix A-2] R1= R2=2KΩ, R3=10 KΩ, R4= R5=2KΩ
3) Add DC Voltage Source (Vs) [Appendix A-5] Vs = ask your engineer
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Simulate the circuit [Appendix A-13]
7) Calculate the equivalent resistor.
1) Start OrCAD [Appendix A-1]
2) Add Resistors [Appendix A-2] R1= 1KΩ, R3=10 KΩ, R2=1KΩ
3) Add DC Voltage Source (Vs) [Appendix A-5] Vs = ask your engineer
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Simulate the circuit [Appendix A-13]
7) Calculate the equivalent resistor.
(a)
(b)
Figure 1-15: Circuit Diagram
I
I
R AB1 = 𝑽𝒔
𝑰 =
R AB2 = 𝑽𝒔
𝑰 =
A B1
VS
10
Equipments:
Procedure:
Part I : Ohm’s Law:
1) Select a discrete resistor R = 4 KΩ, measure the resistor value
2) Measure the resistance of the wires, make sure that its value not equal to OL
3) Connect the circuit as shown in Figure 1-16 with the shown values.
4) Vary the DC voltage source and measure I. Fill table 1-1.
Table 1-1
VS I (mA)
1
3
6
9
12
Q1: Draw I versus V, find the slope of the curve and what does the slope represent?.
Q2: Compare the slope of Q1 with the theoretical value. % 100Theoritical Measured
errorTheoritical
Q3: What are the error sources in Q2?
1) DC Voltage Source 2) Bread Board.
3) DMM 4) Discrete resistors
Figure 1-16: Circuit Diagram
Experimental Work
I
R =
11
Part II: Parallel and Series Circuits:
1) Connect the circuit as shown in Figure 1-17-a, R1= R2=2KΩ, R3=10 KΩ, R4= R5=2KΩ,
Measure RAB1.
2) Connect the circuit as shown in Figure 1-17-b, R1=1KΩ, R3=10KΩ, R2=1KΩ.
Measure RAB2.
Q4: Calculate RAB1 and RAB2 theoretically.
Q5: What is the relation between the circuit of Figure 1-17a and Figure 1-17b
(a)
(b)
Figure 1-17: Circuit Diagram
RAB1=
RAB2=
A B2
A B1
12
Verification of KVL and KCL.
Simulating the DC circuits using OrCAD.
Measuring and calculating the equivalent resistance of different circuits.
Kirchhoff’s Voltage Law (KVL)
KVL states that the algebraic sum of all voltages around a closed path (or loop) is zero. Figure 2-1
shows an example for closed loop circuit.
For the circuit shown in Figure 2-1,
applying KVL:
Figure 2-1: KVL example
Kirchhoff’s Current Law (KCL)
Kirchhoff’s current law (KCL) states that the sum of the currents entering a node is equal to the sum
of the currents leaving the node.
For the circuit shown in Figure 2-2,
applying KCL:
Figure 2-2: KCL example
KVL, KCL, and equivalent circuit resistance 2
Objectives
Theory
13
Parallel and Series Circuit Connections
1 2
1
...N
ab N n
n
R R R R R
11 2
1 1 1 1 1...
N
nab N nR R R R R
Series Connection Parallel Connection
Figure 2-3: Series-Parallel Connections
Delta to Wye Conversion
Delta to Why conversion (given Ra, Rb, Rc)
Why to Delta conversion (given R1, R2, R3)
Figure 2-4: Delta Why conversions
n
n
14
Connect the circuit as shown in Figure 2-5 by the following steps:
Figure 2-5: Circuit Diagram
1) Start OrCAD [Appendix A-1]
2) Add a Resistor [Appendix A-2] (R1=2KΩ, R2=3.9KΩ, R3=1KΩ, R4=5.1KΩ)
3) Add DC Voltage Source (Vdc) [Appendix A-5] (V1= ask your engineer Volt, V2= ask your
engineer Volt)
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Select the bias point simulation analysis [Appendix A-15]
7) Simulate the circuit [Appendix A-13]
8) Activate the voltage and current icons in the tool bar.
9) Fill Table 2-1.
OrCAD Simulation
I1
I2
I3
A
L1
L3 L2
L4
+
-
+ -
-
+ -
-
+ -
-
15
Table 2-1
I1 I2 I3
Q1: Verify KCL at point A.
Delta to Wye Conversion
Figure 2-6: Circuit Diagram
1) Start OrCAD [Appendix A-1]
2) Add a Resistor [Appendix A-2]
3) Add DC Voltage Source (Vdc) between the two nodes A and B = ask your engineer
Volt[Appendix A-5]
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Select the bias point simulation analysis [Appendix A-15]
7) Simulate the circuit [Appendix A-13]
8) Activate the voltage and current icons in the tool bar.
9) Calculate the value of RAB
Rab == 𝑉𝑠
𝐼 =
1KΩ
10KΩ
2KΩ
3.9KΩ
2KΩ
10KΩ
1KΩ
16
Equipment:
Part A – KVL & KCL:
1) Select (using color table in Appendix B-1) and measure (using DMM) the resistors values.
Fill the measured values of the resistors in Table 2-2.
Table 2-2
R1 R2 R3 R4
2) Measure the resistance of the wires, make sure that its value not equal to OL
3) Connect the circuit shown in Figure 2-5, adjust V1 = ask your engineer V and V2 = ask your
engineer V using DMM.
4) Fill table 2-3.
Table 2-3
VR1 VR2 VR3 VR4 I1 I2 I3
Q1: Using the measured values of table 2-2 and 2-3, verify KVL for closed loops L1, L2, and L3.
Loop L1:
Loop L2:
Loop L3:
Q2: Using the measured values of tables 2-2 and 2-3, verify KCL at node A.
a) DC Voltage Source b) Bread Board.
c) DMM d) Discrete resistors.
Experimental Work
17
Q3: Repeat Q1 using results of OrCAD.
Part B - Delta to Wye Conversion and equivalent resistance of different
circuits:
Figure 2-7: Circuit Diagram
1) Connect the circuit as shown in Figure 2-7.
2) Using DMM measure Rab.
Q4: Find Rab theoretically in details (step by step with figures) and compare it with measured value
in step 2 and the simulated value by OrCAD.
Rab =
1KΩ
10KΩ
2KΩ 2KΩ
10KΩ
1KΩ
3.9KΩ
18
Verification of Nodal analysis method.
Verification of Mesh analysis method.
Verification of Superposition technique.
DC circuits analysis using OrCAD.
Nodal Analysis
Analysis Steps:
1. Select a node as the reference node. Assign voltages v1, v2,…, vn-1 to the remaining n−1
nodes. The voltages are referenced with respect to the reference node.
2. Apply KCL to each of the n−1 non reference nodes. Use Ohm’s law to express the branch
currents in terms of node voltages.
3. Solve the resulting simultaneous equations to obtain the unknown node voltages.
Example:
Figure 3-1: Nodal Example
Applying nodal equation for the circuit of Figure 3-1:
1 1 1 1 2
1 3 2
0N N N NV V V V V
R R R
2 2 2 2 1
5 4 2
0N N N NV V V V V
R R R
Nodal, Mesh and Superposition Analysis
3
Objectives
Theory
19
Mesh Analysis
A mesh is a loop which does not contain any other loops within it.
Analysis steps:
1. Assign mesh currents i1, i2, . . . , in to the n meshes.
2. Apply KVL to each of the n meshes. Use Ohm’s law to express the voltages in terms of the
mesh currents.
3. Solve the resulting n simultaneous equations to get the mesh currents.
Example:
Figure 3-2: Mesh Loop Example
Applying mesh loop equation for the circuit of Figure 3-2:
Superposition technique:
The superposition principle states that the voltage across (or current through) an element in a linear
circuit is the algebraic sum of the voltages across (or currents through) that element due to each
independent source acting alone.
Superposition steps:
1. Turn off all independent sources except one source. Find the output (voltage or current) due
to that active source using nodal or mesh analysis.
2. Repeat step 1 for each of the other independent sources.
3. Find the total contribution by adding algebraically all the contributions due to the independent
sources.
Example:
For the circuit shown in Figure 3-1, to find IR1 using super position:
20
Disconnect the voltage source V2 and replace it with a wire (short circuit it) as shown in
Figure 3-3-a.
Solve for IR1’.
Disconnect the voltage source V1 and replace it with a wire (short circuit it) as shown in
Figure 3-3-b.
Solve for IR1”.
IR1 = IR1’ + IR1”
(a) (b)
Figure 3-3: Superposition Technique Example
Connect the circuit as shown in Figure 3-4 by the following steps:
Figure 3-4: Circuit Diagram
1) Start OrCAD [Appendix A-1]
2) Add a Resistor [Appendix A-2], R1=1K, R2=1K, R3= 3.9K, R4= 2K, R5=2K,
R6=10K.
3) Add DC Voltage Source (Vdc) [Appendix A-5], V1 = ask your engineer V and V2 = ask
your engineer V.
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
OrCAD Simulation
IR1’ IR1”
L1 L2 L3
A B
C
21
6) Select the bias point simulation analysis [Appendix A-15]
7) Simulate the circuit [Appendix A-13]
8) Activate the voltage and current icons in the tool bar.
9) Fill Table 3-1.
Table 3-1
IR1 IR4 IR6 VA VB VC
10) Deactivate V2 and simulate the circuit’ [Appendix A-13]
11) Fill table 3-2
Table 3-2
𝑉𝐴′ 𝐼𝑅4
′
12) Deactivate V1 and simulate the circuit” [Appendix A-13]
13) Fill table 3-3.
Table 3-3
𝑉𝐴" 𝐼𝑅4
"
Q1: Verify superposition technique for VA and IR3.
Equipments:
Part A – Nodal and Mesh Analysis
a. Measure the resistance of the wires, make sure that its value not equal to OL
b. For the circuit shown in Figure 3.4, select (using color table in appendix B-1) and measure
(using DMM) the resistors. Fill the measured values of the resistors in table 3-4.
e) DC Voltage Source f) Bread Board.
g) DMM h) Discrete resistors.
Experimental Work
22
Table 3-4
R1 R2 R3 R4 R5 R6
c. Connect the circuit shown in Figure 3-4, adjust V1 = ask your engineer V and V2 = ask your
engineer V using DMM.
d. Fill table 3-5.
Table 3-5
IR1 IR4 IR6 VA VB VC
Q1: Using the measured values of table 3-4 and 3-5, verify Nodal equations for A and B.
Node A:
Node B:
Q2: Using the measured values of table 3-4 and 3-5, verify Mesh equations.
Mesh L1:
Mesh L2:
Mesh L3:
Part B – Superposition technique:
1) Deactivate the voltage source V2, measure and fill table 3-6 for 𝑉𝐴′ and 𝐼𝑅4
′
2) Deactivate the voltage source V1, measure and fill table 3-6 for 𝑉𝐴" and 𝐼𝑅4
"
3) Verify superposition technique and fill table 3-6 for 𝑉𝐴 and 𝐼𝑅4
Table 3-6
𝑉𝐴′ 𝑉𝐴
" 𝑉𝐴 𝐼𝑅4
′ 𝐼𝑅4" 𝐼𝑅4
23
Verification of Thevenin’s Theory.
Verification of maximum power condition.
Determination of Thevenin’s Eq. Circuit using OrCAD.
Thevenin’s Theory
Thevenin’s theorem states that a linear two-terminal circuit can be replaced by an equivalent circuit
consisting of a voltage source VTh in series with a resistor RTh, where VTh is the open-circuit voltage
at the terminals and RTh is the input or equivalent resistance at the terminals when the independent
sources are turned off.
(a) Original Circuit (b) Thevenin Equivalent Circuit
Figure 4-1: Thevenin Theory
Maximum Power Transfer
Maximum power is transferred to the load when the load resistance equals the Thevenin resistance as
seen from the load (RL = RTh).
For Figure 4-2, maximum power equation is as follows:
(1)
Thevenin’s Equivalent Circuit & Max. Power Transfer
4
Objectives
Theory
24
(a) The circuit used for maximum power
transfer
(b) Power delivered to the load as a function
of RL
Figure 4-2: Maximum Power Circuit
Connect the circuit as shown in Figure 4-3 by the following steps:
Figure 4-3: Circuit Diagram
1) Start OrCAD [Appendix A-1]
2) Add a Resistor [Appendix A-2] R1=5.1KΩ, R2=3.9KΩ, R3=2KΩ, RL=1KΩ
3) Add two DC Voltage Source (Vdc) [Appendix A-5] V1= ask your engineer, V2= ask your
engineer
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
Part 1- Finding I through RL:
1) Select the bias point simulation analysis [Appendix A-15]
2) Simulate the circuit [Appendix A-13]
X
I
OrCAD Simulation
Y
25
3) Activate the voltage and current icons in the tool bar.
Part 2: Calculating I using Thevenin’s Circuit
A) Finding VTH
1) Change the value of RL to be 1T (high value equivalent to open circuit).
2) Simulate the circuit [Appendix A-13]
3) Activate the voltage and current icons in the tool bar. Calculate VTH = Vxy
B) Finding RTH
1) Change the value of RL to be 1f (very small value equivalent to short circuit).
2) The circuit will be as shown in Figure 4-4.
3) Simulate the circuit [Appendix A-13]
4) Activate the voltage and current icons in the tool bar.
5) Calculate RTH
Figure 4-4: Circuit Diagram
SC
THTH
I
VR = KΩ
Q1: Using Thevenin Equivalent Circuit, calculate IRL and compare it with the value in part 1.
𝐼𝑅𝐿 =𝑉𝑇𝐻
𝑅𝑇𝐻 + 𝑅𝐿= 𝑚𝐴
Isc
IRL = mA
VTH = V
ISC = mA
26
Equipments:
Part 1 – Finding IRL
1) Measure the resistance of the wires, make sure that its value not equal to OL
2) Connect the circuit as shown in Figure 4-3 with the same values of resistors (using color
resistor table in Appendix B-1). Fill the measured values of the resistors in table 4-1.
Table 4-1
R1 R2 R3 RL
3) Connect the circuit shown in Figure 4-3, adjust V1 = ask your engineer and V2 = ask your
engineer using DMM.
4) Measure I.
Part 2: Calculating I using Thevenin’s Circuit
A) Finding VTH
Remove RL from the circuit and measure VTH = Vxy
B) Finding RTH
Remove RL and replace it with a short circuit wire.
Measure ISC.
Calculate RTH
Q2: Using Thevenin Equivalent Circuit, calculate IRL and compare it with the value in part 1.
i) DC Voltage Source j) Bread Board.
k) DMM l) Discrete resistors and resistor box
Experimental Work
IRL = mA
VTH = V
ISC = mA
RTH = KΩ
IRL = mA
27
Part 3: Maximum Power Transfer
Figure 4-5: Circuit Diagram
Let VTH = 10 V and RTH = 1500 .
Connect the circuit as shown in Figure 4-5, where RL is a resistor box.
Vary RL with the values of table 4-2.
Fill table 4-2.
Table 4-2
RL () I PRL = I2*RL
500
1000
1500
2000
2500
Q3: From table 4-2, plot PRL versus RL. What is the value of RL for maximum power. Comment?
RTH
RL VTH
I
+
-
RL = KΩ PRL MAX = W
28
To be familiar with the Digital Oscilloscope (CRO) and Function Generator (FG).
Using P-Spice to simulate AC circuit analysis.
AC measurements using CRO.
Verifying the relation between Peak-Peak value and RMS values for AC circuits.
Alternating current (AC): the flow of charge is continually changing in magnitude (and direction)
with time.
Sample of AC supply waveforms:
(a) sine wave (b) square wave (c) triangle wave
Figure 5-1: AC waveforms samples
AC Basics:
Figure 5-2: Sinusoidal Waveform
AC Fundamentals and Measurements
5
Objectives
Theory
VPP
VP
29
Frequency F: the number of cycles per second of a waveform in Hz.
The period T: of a waveform is the duration of one cycle in seconds. 1TF
Peak Value: the peak value of a voltage or current is its maximum value with respect to zero.
Peak-to-peak VPP: is the value between minimum and maximum peaks
Root Mean Square (RMS) value:
The effective value of a periodic current is the dc current that delivers the same average power to a
resistor as the periodic current.
(1)
Where: x is v(t) or i(t).
Table 5-1: RMS equations for different waveforms
Wave Form RMS
Sinusoidal wave 2 2
PP
rms
VV
Triangle wave 2 3
PP
rms
VV
Square wave 2
PP
rms
VV
Connect the circuit as shown in Figure 5-3 by the following steps:
Figure 5-3: Circuit Diagram
1) Start OrCAD [Appendix A-1]
2) Add 3 Resistors (R1=5.1KΩ - R2=2KΩ - R3=3.9KΩ - R4=1KΩ) [Appendix A-2]
OrCAD Simulation
A B C
30
3) Add V1 = AC sine wave voltage source (Vsinpp) = ask your engineer V [Appendix A-7]
a. VOFF = 0
b. VAMPL = V1/2
c. FREQ = 1520 Hz
4) Add Ground [Appendix A-11]
5) Connect the circuit by adding wires [Appendix A-10]
6) Add CRO probes to measure both VA and VB [Appendix A-12]
7) Adjust the transient simulation parameters [Appendix A-17]
a. Print step = 0 ns
b. Final time = 2*Time period
c. Tick the skip initial transient solution.
8) Simulate the circuit [Appendix A-13]
9) To get the value of VA-VB , add trace [Appendix A-18]
a. Trace expression = V(A)- V(B)
10) The following wave form will be displayed in a new window.
11) Using the toggle cursor [Appendix A-19], fill table 5-2:
Table 5-2
VA PP VB PP VAB PP Period T (msec)
12) Apply KVL for loop ABA to check your result.
13) Repeat the steps from 1 to 9, modify step 3 to be square wave (VPP = ask your engineer V,
Freq. = 1520 Hz KHz) as follows:
Time
0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0ms
V(R5:2) V(B) V(A)
-8.0V
-4.0V
0V
4.0V
8.0V
31
a. Add square wave voltage source (Vpulse) [Appendix A-8]
i. V1= V1/2
ii. V2= -V1/2
iii. TD= 0
iv. TR= 1p
v. TF= 1p
vi. PW=1
2 .Freq
vii. PER=1
.Freq
14) The following wave form will be displayed in a new window.
15) Using the toggle cursor [Appendix A-19], fill table 5-3:
Table 5-3
VA PP VB PP VAB PP Period T (msec)
16) Repeat the steps from 1 to 9, modify step 3 to be triangle wave (VPP = ask your engineer V,
Freq. = 1520 Hz) as follows:
a. Add triangle wave voltage source (Vpulse) [Appendix A-9]
i. V1= -V1/2
ii. V2= V1/2
iii. TD= 0
iv. TR=1
2 .Freq
v. TF= 1
2 .Freq
vi. PW= 1p
Time
0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0ms
V(R5:2) V(B) V(A)
-8.0V
-4.0V
0V
4.0V
8.0V
32
vii. PER=1
.Freq
17) The following wave form will be displayed in a new window.
18) Using the toggle cursor [Appendix A-19], fill table 5-4:
Table 5-4
VA PP VB PP VAB PP Period T (msec)
Equipments:
Procedure:
Part 1: 1) Measure the resistance of the wires, make sure that its value not equal to OL
2) Connect the circuit as shown in Figure 5-3 with: (R1=5.1KΩ - R2=2KΩ - R3=3.9KΩ -
R4=1KΩ)
3) Adjust the function generator to get sine wave with ask your engineer V PP and freq. = 1520
Hz.
4) Fill table 5-5 by using CRO (use the math function to get VAB).
5) Fill table 5-6 by using DMM.
Time
0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0ms
V(R5:2) V(B) V(A)
-8.0V
-4.0V
0V
4.0V
8.0V
1) Function Generator 2) Bread Board.
3) CRO, DMM 4) Discrete resistors.
Experimental Work
33
Table 5-5
VA PP VB PP VAB PP Period T (msec)
Table 6-6
IR1 RMS VB RMS
6) From table (5-5) calculate VB (RMS) =
Part 2:
7) Adjust the function generator to get square wave with ask your engineer V PP and freq. =
1520 Hz.
8) Fill table 5-7 by using CRO (use the math function to get VAB).
9) Fill table 5-8 by using DMM.
Table 5-7
VA PP VB PP VAB PP Period T (msec)
Table 5-8
IR1 RMS VB RMS
10) From table 5-7, calculate VB (RMS) =
Part 3:
11) Adjust the function generator to get triangle wave with ask your engineer V PP and freq. =
1520 Hz.
12) Fill table 5-9 by using CRO (use the math function to get VAB).
13) Fill table 5-10 by using DMM.
Table 5-9
VA PP VB PP VAB PP Period T (msec)
34
Table 5-10
IR1 RMS VB RMS
14) From table 5-9, calculate VB (RMS) =
Q1: Is the peak to peak values of the voltage or current changed by changing the wave
form?
Q2: Is the RMS values of the voltage or current changed by changing the wave form?
Why?
Q3: Find the RMS value for sine, square and triangle wave using general formula?
Show your work in details
-------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------------------
35
Study the natural response and step response of RL/RC circuits.
Calculate the Time Constant.
When the dc source of an RC circuit is suddenly applied, the voltage or current source can be
modeled as a step function, and the response is known as a step response. The natural response or
transient response is the circuit’s temporary response that will die out with time. The forced response
or steady-state response is the behavior of the circuit a long time after an external excitation is
applied. The complete response of the circuit is the sum of the natural response and the forced
response.
Natural Response
RL Circuit RC Circuit
Figure 6-1 : RL & RC Circuit
( ) , 0t
L oi t i e t
(1)
( ) , 0t
C ov t v e t
(2)
Where :
eq
eq
L
R (3)
is the time constant.
Io is the initial conductor current at t=0.
Where:
eq eqR C (4)
is the time constant.
Vo is the initial capacitor current at t=0.
As shown in figure 6-2 and figure 6-4:
( ) ( )Lx t i t for RL circuit. (5)
Natural-Response of RL/RC circuits
6
Objectives
Theory
+
Vo
- Io
36
( ) ( )Cx t v t for RC circuit. (6)
Figure 6-2 : Natural Response
Step Response
Figure 6-3 : Step Response of RL & RC circuit
( ) (1 ), 0t
sL
Vi t e t
R
(7)
( ) (1 ), 0t
C sV t V e t
(8)
RL Circuit RC Circuit
iL +
Vc
-
37
Figure 6-4 : Step Response
Time Constant : the time required for the natural response to decay by a factor of e-1 (36.8%) as
shown in figure 6-2 or the time for the step response to be 63.3% of its final value as shown in figure
6-4.
Part A: RC Circuit
Figure 6-5: RC Circuit
Connect the circuit as shown in figure 6-5 by the following steps:
19) Start OrCAD [Appendix A-1]
20) Add Resistor [Appendix A-2] R=500Ω
21) Add Capacitor [Appendix A-3] C=0.2uF
22) Add Vs = square wave voltage source (Vpulse) with amplitude VPP= ask your engineer and
frequency =625 Hz [Appendix A-8]
o DC=0
OrCAD Simulation
s
38
o AC=0
o V1= 0
o V2=VS
o TD= 1f
o TR= 1f
o TF1f
o PW= 1
2 .Freq= 0.8m
o PER= 1
.Freq =1.6m
23) Add Ground [Appendix A-11]
24) Connect the circuit by adding wires [Appendix A-10]
25) Add CRO probes to measure both Vs and Vc [Appendix A-12]
26) Adjust the transient simulation parameters [Appendix A-17]
a. Print step = 0.000001 m, Final time = 2ms.
27) Simulate the circuit [Appendix A-13]
28) The output will be displayed in a new window as shown.
11. Trace the simulation [Appendix A-18] to get the time constant :
Trace expression = 6.32 which represents 63.2% of the final value to get the time
constant from the intersection of the 6.32 trace with the charging voltage.
=
12. Measure the value of VC at t = 0.2 msec, then verify this value theoretically by using equation
(8). Calculate the %error.
VC = (simulation)
Time
0s 0.2ms 0.4ms 0.6ms 0.8ms 1.0ms 1.2ms 1.4ms 1.6ms 1.8ms 2.0ms
V(V1:+) V(C1:2) 6.32 3.62
0
5
10
39
VC = (theoretical)
%error=
Part B: RL Circuit
Figure 6-6: RL Circuit
1) Repeat the steps of part A, connect the circuit as shown in figure 6-6 by changing the
capacitor with an inductor=20mH and the value of R to be 2 KΩ [Appendix A-4].
2) Trace the simulation [Appendix A-18] to get the time constant :
Trace expression = 6.32 which represents 63.2% of the final value to get the time
constant from the intersection of the 6.32 trace with the increasing VR response.
=
3) Measure the value of VR at t = 0.3 msec, then verify this value theoretically by using equation
(8). Calculate the %error.
VR = (simulation) VR = (theoretical)
%error =
(Note: ( ) RL
Vi t
R , so the response of IL(t) is the same response of VR(t) divided by constant)
Equipments:
1) Resistor, capacitor, and inductor substitution box.
2) Function Generator.
3) Digital Multi-Meter DMM
4) CRO.
Experimental work
40
Procedure:
Part A: RL Circuit
Figure 6-7: Circuit Diagram Figure 6-8: Pulse Voltage
1) Measure the resistance of the wires, make sure that its value not equal to OL
2) Connect the circuit as shown in figure 6-7,
3) Adjust the function Generator to generate square wave with maximum amplitude= ask your
engineer V and minimum amplitude=0 V, Frequency=625 Hz, as shown in figure 6-8 (by
adjusting the amplitude value and the DC offset).
4) From the CRO screen, measure the value of .
=
5) Calculate the % error between (Practical) and (OrCAD).
(OrCAD) = %error =
6) Calculate the % error between (Practical) and (Theoretical).
(theoretical) = %error =
10
1.6m time
41
Part B: RC Circuit
Figure 6-9: Circuit Diagram Figure 6-10: Pulse Voltage
1) Connect the circuit as shown in figure 6-9,
2) Adjust the function Generator to generate square wave with maximum amplitude= ask your
engineer V and minimum amplitude=0 V, Frequency=625 Hz, as shown in figure 6-10 (by
adjusting the amplitude value and the DC offset).
3) From the CRO screen, measure the value of .
=
4) Calculate the % error between (Practical) and (OrCAD).
(OrCAD) = %error =
5) Calculate the % error between (Practical) and (Theoretical).
(theoretical) = %error =
Q1: Define time constant? τ =RC (for RC circuit)
τ =R
L(for RL circuit)
10
1.6m time
42
Study the sine wave of AC voltage and current.
Measure Phase Shift between voltage and current.
Phase Shift
Phase shift is the angle between voltage and current.
Passive Circuit Elements
A) Resistor
Figure 7-1: Resistor Passive Element
Figure 7-2: Time Domain Response (Voltage and Current are in phase)
Sinusoidal AC Voltage & Current for RL & RC Circuits
7
Objectives
Theory
43
Figure 7-3: Phasor Form
Figure 7-4: Phaseor Diagram ( = 0o )
B) Inductor
Figure 7-5: Inductor Passive Element
Figure 7-6: Time Domain Response (Current lags the Voltage by angle = 90o)
V j LI (1)
Figure 7-7: Phasor Form
Figure 7-8: Phasor Diagram ( = 90o )
V
I
I V
44
C) Capacitor
Figure 7-9: Capacitor Passive Element
Figure 7-10: Time Domain Response (Current leads Voltage by angle = 90o)
1V I
j C
(2)
Figure 7-11: Phasor Form
Figure 7-12: Phasor Diagram ( = 90o )
I
V
90o
45
D) R-L series AC circuit
Figure 7-13: RL Circuit
Figure 7-14: Time Domain Response (Current lags Voltage by angle )
( )V j L R I (3)
Figure 7-15: Phasor Form
1tanL
R
(4)
Figure 7-16: Phasor Diagram 0 90
VR
V
I
V
i
V
j
VL
I
46
E) R-C series AC circuit
Figure 7-17: RC Circuit
Figure 7-18: Time Domain Response (Current leads Voltage by angel )
1V R I
jwC
(5)
Figure 7-19 : Phasor Form
1 1tan
C R
(6)
Figure 7-20 : Phasor Diagram 0 90
VR
V
I
V
V
VC
I
47
Part A: RL Circuit
Figure 7-21: RL Circuit
Connect the circuit as shown in figure 7-21 by the following steps:
1) Start OrCAD [Appendix A-1]
2) Add Resistor (R= 1450 Ω) [Appendix A-2]
3) Add Inductor (L=131 mH) [Appendix A-4]
4) Add Vs = AC sine wave voltage source (Vsinpp) = ask your engineer V [Appendix A-7]
a. VOFF = 0
b. VAMPL = Vs/2
c. FREQ = 2175 Hz
5) Add Ground [Appendix A-11]
6) Connect the circuit by adding wires [Appendix A-10]
7) Add CRO probes to measure both Vs and VR [Appendix A-12]
8) Adjust the transient simulation parameters [Appendix A-17]
d. Print step = 1ns
e. Final time = 2*Time period
f. No-Print Delay = 0.1 ms
g. Tick the skip initial transient solution.
9) Simulate the circuit [Appendix A-13]
10) The output will be displayed in a new window as shown.
OrCAD Simulation
s
48
11. Measure X (the time shift between Vs and Vr).
12. Calculate (phase shift between Vs and Vr), using the following equation:
360X
T (9)
Where T (time period) = 1/Freq.
X =
T =
=
VR Leads or Lags Vs ? ……….
Part B: RC Circuit
Figure 7-22: RC Circuit
Connect the circuit as shown in figure 7-22 by the following steps:
1) Repeat the steps of part (A) except:
a. Step 2 = R = 2280 Ω [Appendix A-2]
Time
0.1ms 0.2ms 0.3ms 0.4ms 0.5ms 0.6ms 0.7ms 0.8ms 0.9ms 1.0ms 1.1ms 1.2ms 1.3ms 1.4ms 1.5ms 1.6ms 1.7ms 1.8ms 1.9ms 2.0ms
V(R4:2) V(V2:+)
-4.0V
-3.0V
-2.0V
-1.0V
0.0V
1.0V
2.0V
3.0V
4.0V
s
49
b. Step 3 = Capacitor (0.084 uF) [Appendix A-3]
c. Add Vs = AC sine wave voltage source (Vsinpp) = ask your engineer V [Appendix A-
7]
i. VOFF = 0
ii. VAMPL = Vs/2
iii. FREQ = 2175 Hz
d. Step 8: Adjust the transient simulation parameters [Appendix A-17]
iv. Print step = 1ns
v. Final time = 2*Time Period
vi. No-Print Delay = 0.1 ms
vii. Tick the skip initial transient solution.
The output will be displayed in a new window as shown
2. Measure X (the time shift between Vs and Vr).
3. Calculate (phase shift between Vs and Vr), using the following equation:
360X
T (10)
Where T (time period) = 1/Freq.
X =
T =
=
VR Leads or Lags Vs ? ……….
(Note : VR represents the response of I in the circuit for both RL and RC Circuit)
Time
2.0ms 2.1ms 2.2ms 2.3ms 2.4ms 2.5ms 2.6ms 2.7ms 2.8ms 2.9ms 3.0ms 3.1ms 3.2ms 3.3ms 3.4ms 3.5ms 3.6ms 3.7ms 3.8ms 3.9ms 4.0ms
V(V2:+) V(R4:2)
-4.0V
-3.0V
-2.0V
-1.0V
0.0V
1.0V
2.0V
3.0V
4.0V
50
Part C: RLC Circuit
Figure 7-23: RL Circuit
Connect the circuit as shown in figure 7-23 by the following steps:
2) Start OrCAD [Appendix A-1]
3) Add Resistor (R= 1200 Ω) [Appendix A-2]
4) Add Inductor (L=168 mH) [Appendix A-4]
5) Add Capacitor (C=0.132 uF) [Appendix A-3]
6) Add Vs = AC sine wave voltage source (Vsinpp) = ask your engineer V[Appendix A-7]
h. VOFF = 0
i. VAMPL = Vs/2
j. FREQ = 1320 Hz
7) Add Ground [Appendix A-11]
8) Connect the circuit by adding wires [Appendix A-10]
9) Add CRO probes to measure both Vs and VR [Appendix A-12]
10) Adjust the transient simulation parameters [Appendix A-17]
k. Print step = 1ns
l. Final time = 2xTime Period
m. No-Print Delay = 0.1 ms
n. Tick the skip initial transient solution.
11) Simulate the circuit [Appendix A-13]
12) The output will be displayed in a new window as shown.
A B
C
s
51
13. Measure X (the time shift between Vs and Vr).
14. Calculate (phase shift between Vs and Vr), using the following equation:
360X
T (9)
Where T (time period) = 1/Freq.
X =
T =
=
VR Leads or Lags Vs ? ……….
Time
0.1ms 0.2ms 0.3ms 0.4ms 0.5ms 0.6ms 0.7ms 0.8ms 0.9ms 1.0ms 1.1ms 1.2ms 1.3ms 1.4ms 1.5ms 1.6ms 1.7ms 1.8ms 1.9ms 2.0ms
V(R4:2) V(V2:+)
-4.0V
-3.0V
-2.0V
-1.0V
0.0V
1.0V
2.0V
3.0V
4.0V
52
Equipments:
Resistor, capacitor, and inductor substitution boxes.
Function Generator.
Digital Multi-Meter DMM
CRO.
Procedure:
Part A: RL Circuit
Figure 7-24: Circuit Diagram Figure 7-25: Sine Wave Voltage Source
1) Measure the resistance of the wires, make sure that its value not equal to OL
2) Connect the circuit as shown in figure 7-23. (R= 1450 Ω) (L=131 mH)
3) Adjust the function Generator to generate sine wave with VPP = ask your engineer V,
Frequency= 2175 Hz, (Note: be sure that the function generator is adjusted to high output
impedance)
4) Measure and fill table 7-1. (VL will be measured by using the math function of the CRO)
Table 7-1
Adjust Measure Calculate
VS VR VL X (ms) T (ms) o
5) Compare calculated with the obtained from OrCAD.
(OrCAD) = %error = (%error=
%calculated
spicecalculated
)
6) Compare calculated with the theoretical obtained from eq. (4).
(theoretical) = %error = (%error= %ltheoretica
ltheoretica
calculated )
Vpp/2
T
Experimental work
s
53
Note: = 2 Freq.
Part B: RC Circuit
Figure 7-26: Circuit Diagram Figure 7-27: Sine Wave Voltage Source
1) Connect the circuit as shown in figure 7-24. R= 2280 Ω , C = 0.084 uF, FREQ = 2175 Hz.
2) Repeat the steps of part A and fill table 7-2.
Table 7-2
Adjust Measure Calculate
VS VR VC X (ms) T (ms) o
3) Compare calculated with the obtained from OrCAD.
(OrCAD) = %error = (%error=
%calculated
spicecalculated
)
4) Compare calculated with the theoretical obtained from eq. (6).
(theoretical) = %error = (%error= %ltheoretica
ltheoretica
calculated )
Note: = 2 Freq.
Vpp/2
T
s
54
Part C: RLC Circuit
Figure 7-28: Circuit Diagram Figure 7-29: Sine Wave Voltage Source
1) Connect the circuit as shown in figure 7-28. R= 1200 Ω , C = 0.132 uF, L=168 mH, F=1320Hz
2) Connect CRO ch1 to point A and ch2 to point B to measure Vs PP and VL PP = Vch1-ch2.
3) Connect CRO ch1 to point B and ch2 to point D to measure VR PP and VC PP =Vch1-ch2.
4) Connect CRO ch1 to point A and ch2 to point D to measure o between Vs and VR PP.
5) Fill table 7-3.
Table 7-3
Adjust Measure Calculate
VS VL PP VC PP VR PP X (ms) T (ms) o Pf
Q1: From table 7-3, verify KVL Σ V = 0.
Vpp/2
T
A B
D
s
55
Q2:
V Vin Vo
Pt3
Pt1 Pt2
NOTE: Both signals have same frequency
1. Complete the following table.
2. Determine the frequency of the input voltage and the output current?
3. Determine the phase shift between Vin and Vo in seconds and degrees.
4. Is the current lag or lead the input voltage? State whether the circuitis RL or RC circuit
Pt # X-axis value Y-axis value
1 0.05 ms 0
2 0.55 ms 0
3 0
0
56
Phase shift measuring between voltage and current.
Calculation of average active, reactive, and apparent powers.
Verification of power balance in the circuit.
Improvement of power factor.
Power definitions
P: Average active power in watts.
Q: Reactive power in vars.
|S|: Apparent power in VA.
S: Complex power = P + j Q in VA.
Power factor
For max max,v IV V I I
v Iphase shift
PF = power factor = cos()
We have three cases as shown in Table 8-1.
Table 8-1
Case Power Factor Phasor Diagram
= 0 Unity power factor (V & I are in phase)
= +ve Lagging power factor (I lags V)
= -ve Leading power factor (I leads V)
V I
I
V
I
V
Sinusoidal steady-state power calculations
8
Objectives
Theory
57
Power triangle
S P j Q (1)
Pf = cos() (2)
P, Q, S calculations
Table 8-2
Case Equations
Voltage Source
max max,v IV V I I
*
max max max max
1 1cos sin
2 2S V I V I jV I
(3)
Resistor
2 2
max max
2 2
V I RP
R
Q = 0, S = P (4)
Inductor
P = 0
2
2max
max
1
2 2
VQ I L
L
S = j Q (5)
Capacitor
P = 0
2
2max
max
1
2 2
V cQ I
c
S = j Q (6)
Note: for any electric circuit, 0, 0, 0S P Q
Power factor improvement
In a typical electric circuit, the current lags the voltage as shown in Figure 8-2. By adding a capacitor
or (adjusting the existing capacitor in the circuit) will be decreased and pf will be improved. The
best value of pf is unity where = 0.
Q
P
S
Figure 8-1: Power Triangle
I
V
j
c
I
V
Figure 8-2: Lagging pf
58
Figure 8-3: OrCAD Circuit Diagram
Connect the circuit as shown in Figure 8-3 by the following steps:
1) Start OrCAD [Appendix A-1]
2) Add 2 Resistors R1= 1KΩ, R3= 2KΩ [Appendix A-2]
3) Add Inductor L1=100 mH[Appendix A-4]
4) Add capacitor C=0.1 uF[Appendix A-3]
5) Add Vs = AC sine wave voltage source (Vsinpp) = ask your engineer V [Appendix A-7]
VOFF = 0
VAMPL = Vs/2
FREQ = 1000
6) Add Ground [Appendix A-11]
7) Connect the circuit by adding wires [Appendix A-10]
8) Add CRO probes to measure both Vs and VR [Appendix A-12]
9) Adjust the transient simulation parameters [Appendix A-17]
Print step = 0 ns
Final time = 2xTime period
No-Print delay = .1 ms
Step ceiling = 0.001 ms
Tick the skip initial transient solution.
10) Simulate the circuit [Appendix A-13]
11) The following wave form will be displayed in a new window.
OrCAD Simulation
S
59
12) Using the toggle cursor [Appendix A-19], fill Table 8-3:
Table 8-3
VPP (R1) Difference in time (X) Phase Shift pf (lead/lag/unity)
13) Change the value of capacitor to 0.25 uF and repeat the step 10.
14) The following wave form will be displayed in a new window:
15) Using the toggle cursor [Appendix A-19], fill Table 8-4:
Table 8-4
VPP (R1) Difference in time (X) Phase Shift pf (lead/lag/unity)
16) Comment on the obtained power factor.
Time
6.0ms 6.2ms 6.4ms 6.6ms 6.8ms 7.0ms 7.2ms 7.4ms 7.6ms 7.8ms 8.0ms
V(L1:1) V(V1:+)
-5.0V
0V
5.0V
60
Equipments:
1) Function Generator
2) CRO, DMM
3) Electronic Bread Board
4) Resistor, capacitor and inductance substitution boxes.
5) Discrete resistors.
Procedure:
Part A – Power Calculations:
Figure 8-4: Circuit Diagram
1) Measure the resistance of the wires, make sure that its value not equal to OL
2) Connect the circuit as shown in Figure 8-4 with the shown values.
3) Adjust the function generator to get sine wave with ask your engineer VPP and freq. = 1 KHz. (Note:
be sure that the function generator is adjusted to high output impedance)
4) Connect the CRO channels to measure VS PP and VR1 PP as shown in Figure 8-4.
5) Measure VPP (R2//L1//C1) = Ch1 – Ch2
6) Fill Table 8-5.
7) Using equations 1 to 6, fill Table 8-6.
Table 8-5
VS PP VR1 PP T between VS & VR1 VPP (R2//L1//C1)
Experimental Work
61
Table 8-6
360T
T
pf
(lead/lag)
PVS QVS PR1 PR2 QL1 QC1
Q1: Verify average active and reactive power balance.
Part B – Power factor improvement:
1) Change the capacitor value to 0.25 uf.
2) Fill Table 8-7.
Table 8-7
Measure Calculate
VS PP VR1 PP T
between VS & VR1
pf
(lead/lag/unity)
Q2: explain the effect of capacitor on the pf.
62
To be familiar with the protective devices for electric wiring.
To study the final circuit diagram
To study the calculation of customer electric energy cost.
The very nature of the grid system is such that power has to be transmitted over large distances. This
immediately creates a problem of voltage drop. To overcome this problem, a high voltage is used for
transmission (275 or 132 kV), the 275 kV system being known as the ‘Super Grid’. We cannot,
however, generate at such high voltages (the maximum in modern generators is 25 kV) and
transformers are used to step up the generated voltage to the transmission voltage. At the end of a
transmission line is a grid substation, where the requirements of the grid system in that area can be
controlled and where the transmission voltage is stepped down via a transformer to 132 kV. The
system voltage is then further reduced at substations to 33 000, 11 000 and 415/240 V.
Figure 9-1: Kuwait Electric Energy System
Electric Wiring & Energy
Consumption
9
Objectives
Theory
275/132 KV
275 KV
415/240 V
11000/415 V
63
Distribution Board (DB):
A distribution board (or panel board) is a component of an electricity supply system which divides an
electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for
each circuit, and safety protective devices, (RCD), in a common enclosure.
Figure 9-2: Distribution Board
64
Figure 9-3: DB 8-ways double busbar
Electric Fuse:
In electronics and electrical engineering a fuse (from the Latin "fusus" meaning to melt) is a type of
sacrificial over-current protection device. Its essential component is a metal wire or strip that melts
when too much current flows, which interrupts the circuit in which it is connected. A fuse interrupts
excessive current (blows) so that further damage by overheating or fire is prevented. Wiring
regulations often define a maximum fuse current rating for particular circuits.
65
Figure 9-4: Electric Fuses
Low Voltage Circuit Breaker (LVCB)
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical
circuit from damage caused by overload or short circuit. Its basic function is to detect a fault
condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse,
which operates once and then has to be replaced, a circuit breaker can be reset (either manually or
automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small
devices that protect an individual household appliance up to large switchgear designed to protect high
voltage circuits feeding an entire city.
Figure 9-4: Low Voltage CB
66
Fuses compared with circuit breakers
Fuses have the advantages of often being less costly and simpler than a circuit breaker for similar
ratings. The blown fuse must be replaced with a new device which is less convenient than simply
resetting a breaker. Some types of circuit breakers must be maintained on a regular basis to ensure
their mechanical operation during an interruption. This is not the case with fuses, which rely on
melting processes where no mechanical operation is required for the fuse to operate under fault
conditions.
Earth Leakage CB and Residual Current Devices (RCD)
In non-technical terms if a person touches something, typically a metal part on faulty electrical
equipment, which is at a significant voltage relative to the earth, electrical current will flow
through him/her to the earth. The current that flows is too small to trip an electrical fuse which
could disconnect the electricity supply, but can be enough to kill. An ELCB detects even a small
current to earth (Earth Leakage) and disconnects the equipment (Circuit Breaker).
Earth Leakage Circuit Breakers and Residual Current Devices are safety devices that offer that
additional protection. These two types of safety devices are used in areas that have high levels of
earth impedance. These devices have the primary purpose of reducing the risk of shock in the
event of a current flow to the earth.
Principle of operation of an RCD
Figure 8-5 illustrates the construction of an RCD. In a healthy circuit, the same current passes
through the line coil and the load, and then back through the neutral coil. Hence, the magnetic effects
of line and neutral currents cancel out. In a faulty circuit, either line-to-earth or neutral-to-earth, these
currents are no longer equal. Therefore, the out-of-balance current produces some residual
magnetism in the core. As this magnetism is alternating, it links with the turns of the search coil,
inducing an electro-motive force (EMF) in it. This EMF in turn drives a current through the trip coil,
causing operation of the tripping mechanism.
Figure 9-5: RCD Circuit
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Lighting circuits
The ‘loop-in’ system, this is the most common of all lighting circuitry and, as the name suggests,
circuit cables simply ‘loop’ in and out of each lighting point figure 9-6.
Figure 9-6: Lighting Circuit
Radial socket-outlet circuits
Most domestic installations use ring final circuits to supply socket outlets, radial circuits are quite
acceptable. The recommendations for such circuits are given in table 9-1. These radial circuits are
shown in figure 9-7.
Table 9-1: Conventional Circuit Arrangements for Radial Socket outlet Circuits.
Protective
Device Size
Protective
Device Type
Maximum
Floor Area Served
Cable Size Number of
Socket Outlets
30 A or 32 A any 75 m 2 4.0 m 2 unlimited
20 A any 50 m 2 2.5 m 2 unlimited
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Figure 9-7: Radial Socket Outlet Circuit
Ring Final outlet circuits
In electricity supply, a ring final circuit or ring circuit (informally also ring main or just ring) is an
electrical wiring technique developed that provides two independent conductors for live, neutral and
protective earth (ground) within a building for each connected load or socket as shown in figures 8-8-
a & 8-8-b. The ring acts like two radial circuits proceeding in opposite directions around the ring. If
the load is evenly split across the two directions, the current in each direction is half of the total,
allowing the use of wire with half the current-carrying capacity. In practice, the load does not always
split evenly, so thicker wire is used.
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Power Consumption
Consumers pay for the electrical energy they consume and NOT for the power. As before, the energy
is related to the power by:
Energy = Power x Time (1)
Example 1: Consider a 1200 W hairdryer. How much does it cost per month if you use it every day
for 15 minutes? The KWh in Kuwait costs 2 fils to the consumer and approximately 20
fils to the government.
Solution: We want the number of KW times the number of hours to find the energy in KWh. The
total time per month is about 15 min/day x 30 days/month = 450 min/month. = 450/60 =
7.5 h/month. So the energy used is 1.2 KW x 7.5 h = 9 KWh. Then, the cost is 180 fils.
Example 2: A refrigerator rated at 1000 W operates one third of time. What does it cost per month?
Assume 2 fils/KWh.
Solution: 1000 W = 1 KW. The number of hours that the fridge is running is 1/3 x 24 h/day x 30
days= 240 h. So. Cost = 1 KW x 240 h x 2 fils/KWh = 480 fils.
Sample of Warning Labels
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Questions:
Q1: What is the function of electric fuse?
Q2: What is the function of circuit breaker?
Q3: What is the function of earth leakage circuit breaker?
Q4: A typical house contains air condition, clothes dryer, range, refrigerator, lighting and other
appliances. Complete table 9-1, given that cost for KWh is 3 fils. Calculate the bill of the house
for July.
Table 9-1 – House Consumption in July
Item Consumption
(KW)
Consumption
Duration (h)
Total
Consumption/Month
Cost
Air Condition 12 12
Clothes Dryer 3 4
Range 0.8 5
Refrigerator 0.4 24
Lighting 0.8 10
Total