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ENGINEERING PRACTICES LABORATORY MANUAL

SUBJECT CODE : GE1X03

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INDEX S.No. NAME OF EXPERIMENT

SAFETY PRECAUTIONS FOR ELECTRICAL ENGINEERING PRACTICE

PREPARATION OF WIRING DIAGARAM

1 HOUSE HOLD WIRING USING SWITCHES AND INDICATOR-LAMP.

2 FLUORESCENT LAMP WIRING

3 STAIRCASE WIRING

4 POWER MEASUREMENT IN 3∅ CIRCUITS

5 CALIBRATION OF AMMETERS AND VOLTMETERS

6 MEASUREMENT OF SINGLE PHASE ENERGY

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SAFETY PRECAUTIONS FOR ELECTRICAL ENGINEERING PRACTICE

While working with electricity, it is necessary that we take all basic safety

precautions. A little loss of concentration or a little carelessness can lead to serve

shocks and fatal accidents. Some of the precautions are given below:

1. In case a person gets into contact with a live conductor, the mains is to be put

off immediately

2. Before attempting to disengage a person in contact with a live wire, one must

insulate one self by standing on a dry rubber mat or wooden boards.

3. While working on a circuit, the corresponding fuse carrier should be taken

away.

4. In the case of a fire, water should not be thrown on the live conductor.

5. The earthing has to be maintained well

6. The switch is always to be connected on the live conductor.

7. In the case of an electric shock, after giving first aid, call a doctor. Continue

first aid till the doctor takes over.

8. Use wooden or PVC insulated handle screws drivers when working on

electrical circuits.

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PREPARATION OF WIRING DIAGARAM

Wiring is the method of drawing or laying wires or cables and connecting

accessories and fitting s for the purpose of distributing electrical power to the

various points or equipment from the mains.

Durability – Any wiring system must be able to withstand wear and tear

due to weather. The atmospheric action should not affect the wiring

system.

Safety – Safety is the most important point to be considered in the

selection of any wiring system. The wiring should be perfectly leak proof.

Selection of the wire should be according to the ISI standard and the wire

sheet be of such a capacity that it can withstand the total load of the whole

installation.

Mechanical Protection – The wiring should be mechanically sound. It

should be properly protected from damages of physical nature

Appearance – The appearance of the wiring has an important bearing on

the architectural beauty of an edifice from the aesthetic point of view.

Normally conduct wiring embedded under plaster is the proper choice for

improving the appearance of a wiring system.

Environmental Conditions – In places where corrosive acids and alkalis

are to come in contact with wiring systems have to be protected against

fumes and dampness.

Accessibility – Facility for extension and renewal should be provided. The

wiring system adopted should be economical and should suit the

individual. Consumer initial cost be minimized

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Expt No:1 HOUSE HOLD WIRING USING SWITCHES AND

INDICATOR-LAMP. Aim:

1. To control the given lamp using a single switch.

2. To control two lamps connected in series using a switch.

3. To control two lamps connected in parallel using a switch.

Material required :

S.No Components Quality

1 Switch 1 No

2 Test Lamp 2 No

3 3 pin socket(5A) 1 no

4 Connecting wires As required

Tools Required:

Wire man’s tool Kit - 1 No

RULES FOR WIRING

1. The total lighting load in a sub circuit, should not be more than 800W or ten

points whichever is less. The maximum power load in a sub circuit is not to

exceed 2000W or two points whichever is less.

2. Every appliance must be controlled by a switch

3. The switch should be on the live conductor

4. Every socket output must also be controlled by a switch

5. All incandescent lamps are to be atleast 2.5m above and ceiling fans 2.75 m

above floor level.

6. All the metal covering (covers of the main switch, paper, brackets fans etc.,)

should be earthed.

7. The light and power wiring should be separate.

8. Every sub- circuit must have a separate distribution fuse.

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9. The switch and starters of the motor should be easily accessible.

Theory:

Series Circuit: The series circuit provides a single, continuous path through

which current flows. In this the devices are connected one after another and the

current flows through them until it returns to the power source.

Parallel Circuit: In parallel circuit the device are connected side-by-side so that,

current flows in a number of parallel path.

Status

Switch Lamp

0 OFF

1 ON

N

P

230V,50Hz,Ac mains

A LAMP CONTROLLED BY A SWITCH

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STATUS

Switch L1(Lamp) L2(Lamp)

0 OFF OFF

1 ON ON

N

P

230V,50Hz,Ac mains

TWO LAMPS CONNECTED IN SERIES

L1 L2

Switch

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TWO LAMPS CONNECTED IN PARALLEL

STATUS

Switch L1 L2

0 OFF OFF

1 ON ON

N

P

230V,50Hz,Ac mains

L1 L2

Switch

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Result:

Thus the lamps are connected in series and parallel by using a switch.

P

N

Earth

Switch2 Switch1

L1 L2

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Expt No: 2 FLUORESCENT LAMP Aim :

To make connections of a fluorescent tube and to study the accessories of

the same.

Materials Required:

S.No Components Quality

1 Fluorescent tube light fitting 1 set(40 W,240 V)

2 2 way connector 1 No

3 PVC copper cables As required

4 Wood Screws 2 Nos

5 Test Lamp 1 No

Tools Required:

Wire man’s tool Kit - 1 No

Procedure: Assembly of Fluorescent Tube:

I. Assemble the fluorescent tube accessories like starter holder , holder

for tube and choke in the fitting base with the help of screws.

II. Finally the tube is fixed in the tube holder to light it.

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Theory:

1. The electrode of the starter which are enclosed in a gas bulb filled with

argon gas , cause discharge in the argon gas with consequent heating.

2. Due to heating , the bimetallic strip bends and causes in the starter to

close. After this , the choke , the filaments (tube ends) to tube and starter

becomes connected in series.

3. When the current flows through the tube end filaments the heat is

produced. During the process the discharge in the starter tube disappears

and the contacts in the starter move apart.

4. When sudden break in the circuit occur due to moving apart of starter

terminals, this causes a high value of e.m.f to be induced in the choke.

5. According to Lenz’s law ,the direction of induced e.m.f in the choke will

try to oppose the fall of current in the circuit.

6. The voltage thus acting across the tube ends will be high enough to cause

a discharge to occur in the gas inside the tube. Thus the tube starts

giving light.

7. The fluorescent lamp is a low pressure mercury lamp and is a long

evacuated tube. It contains a small amount of mercury and argon gas at

2.5 mm pressure. At the time of switching in the tube , mercury is in the

form of small drops. Therefore , to start the tube , filling up of argon gas is

necessary. So , in the beginning , argon gas starts burning at the ends of

the tube; the mecury is heated and controls the current and the tube starts

giving light. At each end of the tube , there is a tungsten electrode which is

coated with fast electron emitting material . inside of the tube is coated

with phosphor according to the type of light.

8. There are two types of starters. A starter helps to start the start the tube

and break the circuit. They are (i)Thermal type (ii

)glow type.

9. The choke coil is also called blast. It has a laminated core over which

enameled wire is wound. The function of the choke is to increase the

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voltage to almost 1000V at the time of switching on the tube and when the

tube starts working, it reduces the voltage across the tube and keeps the

current constant.

Choke(or)

blast

Result:

Thus the fluorescent lamp circuit is studied and assembled

P N

230V,Ac supply

Starter

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Expt No: 3 STAIRCASE WIRING Aim: To control a single lamp from two different places. Materials Required:

S.No Components Quality 1 Incandescent Lamp 1(230 V,40W) 2 Two way switches 2 3 Lamp holder 1 4 Connecting Wires As required 5 PVC Pipes As required 6 L-Joint As required 7 Clamp and screws As required 8 Mounting block. As required

Tools Required: Hammer, Wire mans tool Kit. Procedure:

1. Give the connections as per the circuit diagram using PVC pipes in

the wooden board.

2. Verify the connections.

3. Switch on the supply.

4. Verify the conditions.

Explanations 1. A two way switch is installed near the first step of the stairs. The

other two way switch is installed at the upper part where the stair

ends.

2. The light point is provided between first and last stair at an

adequate location and height if the light is switched on by the

lower switch. It can be switched off by the switch at the top or vice

versa.

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3. The circuit can be used at the places like bed room where the

person may not have to travel for switching off the light to the

place from where the light is switched on.

4. Two number of Two-way switches are used for the purpose. The

supply is given to the switch at the short circuited terminals.

5. The connection to the light point is taken from the similar short

circuited terminal of the second switch. Other two independent

terminals of each circuit are connected through cables.

CONDITIONS:

Position of

switches

S1 S2

Condition Of

Lamp

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RESULT:

Thus the circuit to control the single lamp from two different places is

studied and verified.

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Expt.No.4 POWER MEASUREMENT IN 3∅ CIRCUITS. AIM: To measure the power consumed by given three phase inductive load

using two wattmeter method, and also determining the power factor.

APPARATUS:

S.No Name of the Apparatus

Range Type Quantity

1 Ammeter (0 – 10)A MI 1 2 Wattmeter 600V,10A UPF 2 3 Load - Resistive 1 FORMULA USED:

1. Total power P = W1+W2 (W)

2. ∅ = Tan-1 √3[W1-W2/W1+W2]

3. P.F = Cos∅.

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CIRCUIT DIAGRAM:

A

440,3phase ac supply



B

R

Y

10A

10A

10A

600V,10A UPF Wm

(0-10)A MI

3 phase variable resistive load

T P S T

600V,10A UPF Wm

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TABULAR COLUMN: SNO I W1 W2 POWER

P P.F

(Amps) (Watts) (Watts) Watts COS∅

PROCEDURE:

1. Connections are given as per the circuit diagram.

2. AC supply is given by closing the TPST switch with no load included in

the circuit

3. Vary the load and note current and both the wattmeter readings.

4. Power and power factor are calculated using the given formula and

tabulated.

FORMULA USED:

1. Total power P = W1+W2 (W)

2. ∅ = Tan-1 √3[W1-W2/W1+W2]

3. P.F = Cos∅.

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RESULT: Thus the Power and Power factors for the given resistive load are

measured and tabulated.

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Ex.No. CALIBRATION OF AMMETERS AND VOLTMETERS Date: Aim To calibrate the given ac and dc ammeters and voltmeters. Apparatus required


Range Type Quantity

1 Ammeter (0 – 10)A MI 2 2 Ammeter (0 – 10)A MC 2 3 Voltmeter (0 – 300)V MI 2 4 Voltmeter (0 – 300)V MC 2 5 Load - Rheostat 1 6 Single Phase

autotransformer 300V,5A - 1

Formula:

a) Percentage Error = (At – As) * 100 / At

b) Percentage Error = (At – As) * 100 / At

c) Percentage Error = (Vt – Vs) * 100 / Vt

d) Percentage Error = (Vt – Vs) * 100 / Vt

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Circuit Diagram

a) DC AMMETER

b) AC AMMETER

10 A

Tested Ammeter

Standard Ammeter

Loading Rheostat

(0-10)A MI

(0 – 10)A MI

230V AC Supply

P

N

SPST

At

As

10A

10 A

Tested Ammeter

Standard Ammeter

Loading Rheostat

(0-10)A MC

(0 – 10)A MC

220V DC Supply

+

-

D P S T

At As

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c) DC VOLTMETER

d) AC VOLTMETER

5 A

(0 – 300)V MI

(0– 300)V MI

230V AC Supply

P

N

SPST

Single phase Autotransformer

Vt

Vs

5A

5 A

(0 – 300)V MC

400 ohms/ 1.5A

(0–300)V MC 220V DC

Supply

+

-

D P S T

+

- -

+

Vt Vs

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Procedure a) i)Connections are given as per the circuit diagram

ii) Close the DPST switch

iii) Vary the load, take the readings of both the ammeters and

tabulate them.

iv) Calculate the error and plot the graph between Percentage error

vs Current

b) i) Connections are given as per the circuit diagram

ii) Close the SPST switch

iii) Vary the load, take the readings of both the ammeters and

tabulate them.


vs Current

c) i) Connections are given as per the circuit diagram

ii) Close the DPST switch

iii) Vary the rheostat, take the readings of both the voltmeters and

tabulate them.


vs Voltage.

d) i) Connections are given as per the circuit diagram

ii) Close the SPST switch

iii) Vary the autotransformer, take the readings of both the

ammeters and tabulate them.


vs Voltage

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Model Graph

Result Thus the given ac and dc voltmeters and ammeters are calibrated.

Percent Error

Voltage or Current

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Expt. No.6 MEASUREMENT OF ENERGY

AIM: To measure the energy consumed in a single phase circuit. APPARATUS REQUIRED


Range Type Quantity

1 Ammeter (0 – 10)A MI 1 2 Voltmeter (0 – 300)V MI 1 3 Load - Rheostat 1 4 Energymeter 300V,10A,

single phase UPF 1

NAME PLATE DETAILS:

RATED CURRENT

RATED VOLTAGE

FREQUENCY

REVOLUTIONS/KWH

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CIRCUIT DIAGRAM

V

A

P

N

SPST 10A

(0-300)V MI

(0-10)A MI

Single phase Energymeter

230V,single phase ac supply

Loading Rheostat

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PROCEDURE: 1.Connections are given as shown in the circuit diagram. 2.Supply is switched ON and load is increased in steps, each time noting the readings of ammeter and wattmeter. Also the actual time taken for 1 revolution of the disc is measured using stop watch. 3.Step 2 is repeated till rated current of the energymeter is reached. 4. % Error is calculated and calibration curve is drawn. TABULAR COLUMN: S.NO LOAD

CURRENT I (Amps)

WATTMETERREADING t (Sec)

INDICATEDPOWER W1 (watts)

% ERROR

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CALCULATION: Let x revolution / kwh be the rating. Now x revolution = 1 kwh = 1* 3600*1000* watt-sec. Constant k of energymeter = 3600 * 103/x watt-sec For each load indicated power Wi is given as Wi = k/t watts Where k→ energymeter constant (watt-sec) t→ time for 1 revolution(sec). Actual power is indicated by the wattmeter reading. % error = Wi-Wa/Wi* 100. It can be zero +ve or –ve. MODEL GRAPH: COCLUSION AND REMARKS: From the calibration curve it is possible to predict the error

in recording the energy. So the correction can be applied to the energymeter reading so that correct energy reading can be obtained and used.

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