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Virtual Laboratory Manual

For

Basic Electrical Engineering

Department of Electrical Engineering

DELHI TECHNOLOGICAL UNIVERSITY

(FORMERLY DELHI COLLEGE OF ENGINEERING)

BAWANA ROAD,DELHI-

LAB COMMITTEE MEMBERS

1. Prof. Uma Nangia (Head of Department)
2. Prof. N.K.Jain (Chairman)
3. Shri N.K.Bhagat (Member)
4. Dr.Rinchin Wanzom Mosobi (Member)
5. Mrs.Shatakshi Jha (Member)
6. Dr.Avirup Maulik (Member)
7. Mr.Gaurav Kaushik (Member)
8. Mr.Rohan Pillai (Member)
9. Mr. Abhishek Chaudhary (Member)
10. Mr.Shreyansh Upadhyaya (Member)

PREFACE Basic Electrical Engineering is a compulsory subject for undergraduate students of all engineering disciplines. This course has a practical component wherein the students perform experiments in laboratory which enhances their understanding of knowledge learnt from classroom lectures. Unfortunately, due to prevailing COVID-19 pandemic situation, it is not possible for students to get hands-on experience. This manual of Virtual Lab of Basic Electrical Engineering has been primarily written for UG students of this semester. This manual covers a total of eight (08) experiments. Five (05) of them are on network theorems and three (03) are on basic concepts of electrical engineering. The steps to conduct an experiment on online virtual platform have been explained elaborately. Video recording of each experiment has also been prepared. It took about two months to prepare this manual. All the discussions regarding experiments were held online and it was a unique experience for all the committee members. This manual is the outcome of comprehensive effort of all the committee members under the expert guidance of Prof. N.K. Jain. I am thankful to Prof. N.K. Jain and all the committee members for their dedicated effort to prepare this manual for virtual lab required under this extraordinary situation.

Table of Contents

Figure 1

3. Never apply full voltage to motor at the time of starting. Use starter or a variac. Apply low voltage while by switching-on & increase voltage gradually.
4. Gradually apply & switch-off an Electrical Load.
5. Keep all meters/instruments used for experiment in their proper position.
6. Any live terminal shouldn’t be touched while supply is on.
7. Supply should be switched-on only after ensuring the correctness of connections. TREATMENT OF ELECTRIC SHOCK VICTIM
8. Immediately switch-off power supply.
9. if switch is away or it is difficult to identify switch, pull out the plug top.
10. Pull the victim away using dry wooden stick, dry rope or dry cloth.
11. Make sure that electrical connections are right & tight.
12. Circuit should be switched-off before changing any connection.
13. Use sufficiently long wires, rather joining two or three small ones. In this case you have open joints which are DANGEROUS.
14. Familiarize yourself with the shock chart instructions.
15. You can also pull away the victim by hand provided you are well insulation from the ground (Standing on insulator or wearing rubber soled shoes).
16. Cut the conductor using some device/tool with insulated handle.
17. Once the Victim is disconnected from supply, he should be treated for recovery as soon as possible. Any one of the Three Methods of Artificial Respiration can be used. Mouth to Mouth Artificial Respiration Following steps should be followed for this process
18. Lay the victim on the back with his head slightly down, so that his chin points upwards.
19. To allow proper breathing clear victim’s neck from clothing etc.
20. Take deep breath and blow it into victim’s mouth until his chest rises.
21. Keep victim’s noses pinching with your thumb and fore finger. Remove your mouth for victim to exhale.
22. Repeat this process as fast as you can.

Figure 2

Schafer’s Method of Artificial Respiration

1. Lay the victim on the stomach with his face on one side.
2. To allow proper breathing clear victim’s neck from clothing etc.
3. Kneel over the victim(refer fig.a)

Figure 3

4. Place your both hands flat on his back in such a manner that both of your thumbs nearly touch each other and fingers spread.
5. Lean forward over the victim gradually keeping your elbow straight.
6. While doing so put your weight on victim for a moment(refer fig.b)
7. Slowly release the pressure & come to the original position.

8. Then bring the arms on each side of chest,so as to compress the chest (Figure 4).
9. Keep position for 2-3 seconds.
10. Repeat the process until the victim starts breathing the normal.
11. Method useful when victim cannot conveniently lie on his stomach. SUPPLY SYSTEMS Available Supply Systems: (a) A.C.Supply Systems These are two types mainly: (i) Single Phase-230volts: In this system we have two wires,one is known as Phase/Line & the other are known as neutral.

Figure 6

(ii) Three Phase-430volt(Line to Line)

1. This system may have three wires, one for each phase/line.
2. This system may also have four wires, three for phase/line & one for neutral. (b)D.C.Supply Systems These are of two types namely, (i)From Battery-6V or 12V:
3. We may use rectifiers for 6V or 12V d.c. supply for lower requirements if regular 6V or 12V supply is not available in laboratory.
4. This system has two wires, one being +ve & other-ve. (ii)From D.C. Generator (or A.C. & Rectifier)
5. It is 230 volts d.c.

Figure 7: Supply From a D.C. Generator

2. It has two wires one being +ve & other being -ve. Systems to Obtain Variable Voltage Supply from the Available Supply System. (a) D.C.Circuit: It consists of a tubular resistance having three terminals.The two end terminals A and B are fixed and represent the two ends of a resistance. The third terminal C is a moving contact which slides over AB. The fixed D.C voltage is applied across AB and a variable D.C. Voltage across CB where C is positive and B is negative is obtained.When the sliding contact C is at B and A, the D.C. voltage is zero and equal to supply voltage respectively.

Figure 8: Obtaining a variable supply from D.C. source

(b)A.C. Circuit:Here we can get A.C. voltage by replacing a rheostat by auto-transformer, also known as Variac/Dimmerstat. It is a coil wound on a magnetic core with its two ends A and B brought out and sliding contact C. It is capable of

(c) Three Phase Circuit:If three single phase variacs are connected in Star-form, it is called three phase variac.When the tapping points are all near the neutral the voltage is small whereas if they are near the line terminals the output voltage is large. Any one limb can be used as a single phase variac.

Figure 10: Obtaining a Variable Supply from a Three Phase A.C. Source

RHEOSTAT

The salient features of a rheostat are:

1. Made up of high resistivity materials like nickel-chromium-iron alloy closely wound over a circular tube.

Figure 11

2. Available in single and double tube.
3. Inter turn insulation is provided to avoid short circuiting of the turns.

Figure 12

4. These are employed at places where resistance of a circuit is to be varied without breaking the circuit.
5. Normally it is 1000Ω,1.2 A and 100Ω, 5A. PLOTTING A GRAPH Some important points to be kept in mind while drawing graphs are:
6. Graphs are drawn to provide a visual of relationship between two quantities.

11. DISCUSSION: This section contains,results,conclusions,comparison of the results and anything important about the aim of the experiment and the apparatus used can be mentioned here.

Experiment No. Aim: To Verify Superposition Theorem Link: http://vlabs.iitkgp.ernet.in/asnm/exp5/index.html#l Theory: If a number of voltage or current source are acting simultaneously in a linear network, the resultant current in any branch is the algebraic sum of the currents that would be produced in it, when each source acts alone replacing all other independent sources by their internal resistances. Circuit Diagram:

Figure 13: Circuit analysis of Superposition theorem

Figure 14: Circuit with only V 2 short circuited Figure 15: Circuit with only V 1 short circuited

In the given figure 1 apply superposition theorem, let us first take the sources

Figure 16: Circuit for analysis of Superposition theorem

3. Set S1 to positions ”aa” and S2 to position ”dd” respectively which means the, only 220V source is energized and the terminals of S2 are shorted. Note down current I 1 ′^ , I 2 ′^ and I 3 ′^ from the ammeter A1, A2 and A3.
4. Set S1 to position ”bb” and S2 to position to ”cc” respectively. Which means the, only 110V source is energized and the terminals of S1 are shorted. Note down current I 1 ′′^ , I 2 ′′^ and I 3 ′′^ from the ammeter A1, A2 and A3.
5. Compare I 1 , I 2 and I 3 with I 1 ′^ + I 1 ′′^ , I 2 ′^ + I 2 ′′^ and I 3 ′^ + I 3 ′′^ taking care of signs properly of verify the theorem.
6. Repeat the step (2) to (6) for five different values of resistance for each three rheostats.

Simulation: The simulator for this experiment is designed based on JavaScript platform combined with HTML5 Canvas for graphics. So, the users are recom- mended to use browsers with HTML5 compatible.

Link to perform simulation: http://vlabs.iitkgp.ernet.in/asnm/exp5/ js-simulator/superposition_website_17mar.html

Figure 17: Simulation Circuit Diagram