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Elements of Engineering Practices Lab Manual & Observation Book

ELECTRICAL ENGINEERING

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

EXPERIMENT NO: 1 THEORY: ONE-WAY SWITCH A one way switch is a basic electrical device used to operate any household electrical or electronic equipment. It works on the principle of make or break. One way switches are regular switches widely used for commercial purpose. The light switch in your room is a one way switch, i.e. the light can be switched on or off from that particular switch only. The different views of one way switch are as shown in Fig 1.1

Fig;1.1

TWO-WAY SWITCH Two way switch can connect one point to the electrical circuit and disconnect the other at the same time. Assume two points A and B in a circuit. When A is connected, B is disconnected and vice versa. Two-way light control is mostly used in the staircase light application. Two switches are placed near to stairs at two ends, when we turn ON/OFF the switch at any end the light present state changes to the opposite state, if light presents in ON condition then it becomes OFF, if light present in OFF condition then it becomes ON. The different views of two way switch are as shown in Fig 1.2

Fig;1.2

INTERMEDIATE SWITCH An intermediate switch is a three way light switch. It is used when you have three or more switches controlling one light, the middle switch needs to be an intermediate light switch . The different views of intermediate switch are as shown in Fig 1.3

Fig 1.3

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

In an intermediate switch, there are four terminals by which it changes the flowing of electric current from one circuit to another and also known as three way switch. It has the ability to ON and OFF the electric supply by two ways. The four terminals of intermediate switch construction and its operation are shown in fig below where the 4 contact points may be known as 1,2, 3 & 4. When the switch knob is up, the terminal contacts of intermediate switch connect terminal 1 with terminal 3 and terminal 2 with terminal 4. On the other hand when knob is down, terminal 1 is connected to terminal 2 and 3 to 4 . ONE-WAY, TWO WAY AND THREE WAY CONTROL OF INCANDESCENT LAMP AIM: To control the given lamp from one, two and three different positions. APPARATUS: Switch Board, Connecting Wires ONE-WAY CONTROL

Fig.1.4: One-Way Control SWITCHING TABLE NO : 1

Sl. No.

Switch S

Lamp Condition

1.

Closed

ON

2.

Open

OFF

PROCEDURE: 1. Connections are made as shown in the circuit diagram of Fig1.4. 2. Switch ON the AC supply mains and close the SPST switch S. Observe the lamp glow condition(as shown in table no.1 3. Open the SPST switch S and observe the lamp glow condition. 4. Switch off the AC supply mains.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

TWO-WAY CONTROL CIRCUIT DIAGRAM:

Fig.1.5: Two-Way Control SWITCHING TABLE NO : 2

Sl. No.

Switch 1(S1) Position Switch 2(S2) Position

Lamp Condition

1.

A

B1

OFF

2.

A

B

ON

3.

A1

B

OFF

4.

A1

B1

ON

PROCEDURE:

1. Connections are made as shown in the Fig. 1.5. 2. Switch ON the AC supply mains and close the SPDT switch. 3. Verify the state of the lamp(as shown in table no.2) for the different combinations of the switch positions. 4. Switch off the AC supply mains.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

THREE –WAY CONTROL CIRCUIT DIAGRAM: a) CIRCUIT DIAGRAM

Fig.1.6 Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

SWITCHING TABLE NO: 3

Sl. No.

Switch 1(S1) position

Switch 2(S2) position

Intermediate Switch

Lamp condition

Position 1.

A

B1

2.

A

B

3.

A1

B

4.

A1

B1

5.

A

B1

6.

A

B

Cross Connection

OFF

7.

A1

B

(C)

ON

8.

A1

B1

OFF Straight Connection (S)

ON OFF ON ON

OFF

PROCEDURE: 1. 2. 3. 4. 5. 6. 7.

Connections are made as shown in the Fig.1.6. Keep the intermediate switch in Straight – connection(S) mode. Switch ON the AC supply mains. Verify the switching table for straight connection(as shown in table no.3). Change the position of intermediate switch to Cross –connection(C) mode. Verify the switching table for Cross- connection(as shown in table no.3). Switch OFF of the main supply and remove the connection.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

a)

OBSERVATION OF THE EXPERIMENT :

b)

TABLE OF EVALUATION : PARTICULARS

MAX.MARKS

Date Sheet

03

Viva

03

Result

04

Total

10

MARKS OBTAINED

Signature of the faculty:

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

EXPERIMENT NO: 02 THEORY: FLUORESCENT LAMP: Fluorescent lamps are cylindrical glass tubes that are coated on the inside with phosphors. They contain a small amount of mercury and are filled with a small quantity of argon, a combination of argon and neon, or krypton gases. During operation, an electrical current passes through the lamp and the mercury is vaporized, producing ultraviolet light. The phosphor coating absorbs the ultraviolet light and re-radiates it as visible light. Fluorescent lamps require ballasts to provide the starting voltage and limit the electrical current during lamp operation. There are two types of ballasts commonly available for residential lighting: the energy-efficient magnetic ballast and the electronic ballast. The majority of ballasts sold today are energy-efficient magnetic types. Electronic ballasts are attractive because they are more energy-efficient than magnetic ballasts. They offer the advantages of lighter weight, quieter operation, and reduction of flicker, but they cost more than magnetic ballasts. Although fluorescent lamps all have tubular-shaped glass bulbs, the tubes can be bent into several shapes. The names for various shapes, and for shapes combined with ballasts and accessories, often are manufacturer-specific. The constructional view, choke and schematic are as shown in Fig

2.1

Fig. 2.1 INCANDESCENT LAMP: The electrical light source which works on the principle of the incandescent phenomenon is called Incandescent Lamp. In other words, the lamp working due to glowing of the filament caused by electric current through it is called an incandescent lamp. The filament of incandescent lamps is airtightly evacuated with a glass bulb of suitable shape and size. This glass bulb is used to isolate the filament from surrounding air to prevent oxidation of filament and to minimize convention current surrounding the filament hence to keep the temperature of the filament high. The glass bulb is either kept vacuum or filled with inert gases like argon with a small percentage of nitrogen at low pressure. Inert gases are used to minimize the evaporation of filament during service of the lamps. But due to the convection flow of inert gas inside the bulb, there will be greater chances of losing the heat of filament during operation. Again vacuum is a great insulation of heat, but it accelerates the evaporation of filament during operation. In the case of gas-filled incandescent lamps, 85% of argon mixed with 15% nitrogen is used. Occasionally krypton can be used to reduce filament evaporation because the molecular weight of krypton gas is quite higher. But it costs greater. At about 80% of

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

atmospheric pressure, the gasses are filled into the bulb. Gas is filled in the bulb with the rating more than 40 W. But for less than 40 W bulb; there is no gas used. The most widely used filament material now a day is tungsten because of its high luminous efficacy. It can give 18 lumens per watt when it operates at 2000 oC. This efficacy can be up to 30 lumens per watt when it operates at 2500 oC. The high melting point is a major criterion for filament material as it has to work at very high temperature without being evaporated. Although tungsten has the little bit poorer melting point than that of carbon still tungsten is more preferable as filament material. This is because of high operating temperatures which makes tungsten much luminous efficient. The mechanical strength of tungsten filament is quite high to withstand mechanical vibrations. The constructional view of incandescent lamp is as shown in Fig 2.2

Fig. 2.2

COMPACT FLUORESCENT LAMPS (CFL): A compact fluorescent lamp (CFL), also known as a compact fluorescent light or energy saving light, is a type of fluorescent lamp. Most CFLs are designed to replace incandescent lamps and fit into most existing light fixtures. Compared to general service incandescent lamps giving the same amount of visible light, CFLs use less power and have a longer rated life. Downside is they have a higher purchase price. Like all fluorescent lamps, CFLs contain mercury, which complicates their disposal. CFLs radiate a different light spectrum compared to incandescent lamps. New phosphor compositions have improved the colour of the light emitted by CFLs in such a way that the best warm white CFLs are nearly similar in colour to standard incandescent lamps. Its view is shown in Fig. 2.3

Fig .2.3 LIGHT EMITTING DIODE(LED) LEDs ( Light Emitting Diodes) normally consist of a single p-n junction diode. A diode is the basic building block of solid state electronics and is the simplest possible semiconductor device. The fundamental electrical property of a semiconductor diode is that it only allows electric current to flow in one direction, but how does it do that? Most semiconductors are made of a poor conductor such as silicon and germanium that has had atoms of another material deliberately added to it. This process of Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

adding these impurities is often called doping. The original pure material is electrically neutral and has exactly the right number of electrons associated with each atom, meaning there are neither too many nor too few electrons and so there are no free electrons available to carry electric current. However the doping process of adding extra atoms moves some of the electrons in the material and can leave a material with either more free electrons than it needs in some parts or with too few, thus leaving positively charged holes where electrons can fit. Both these changes make the material more able to conduct an electric current. In normal terminology the material with extra electrons is called N-type, since those extra electrons are negatively charged particles, and the material with a deficit of electrons (or surfeit of holes) is called P-type. Because of the electrostatic attraction between positive and negative particles free electrons are attracted towards the positively charged holes. The working principle and image are as shown in Fig.2.4

Fig. 2.4 2a). POWER FACTOR MEASUREMENT OF FLUORESCENT LAMP WITH AND WITHOUT CAPACITOR AIM: To measure power factor of Fluorescent lamp with and without the capacitor. APPARATUS REQUIRED: One (0-1A) AC ammeter, one (0-300V) AC voltmeter, one (1/2A, 250V, LPF wattmeter), one Capacitor 2µF and connecting wires.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

CIRCUIT DIAGRAM:

Fig .2.5: Measurement of power and power factor of fluorescent lamp PROCEDURE: 1. 2. 3. 4. 5.

Connections are made as shown in the circuit diagram of Fig 2.5 (including the capacitor). The main supply switch is closed and readings of all meters are noted down. Switch OFF the supply and remove the capacitor connection from the circuit. The main supply switch is closed again and readings of all meters are noted down. Switch OFF the AC supply mains and remove the connections.

TABULAR COLUMN:

Sl. No

Condition

1.

Voltmeter reading

Ammeter reading

Wattmeter reading

(V) volts

(A) amps

(W * Constant) watts

Power (P)

Power Factor (PF)

With Capacitor Without Capacitor

2.

CALCULATIONS:

1. Wattmeter Constant : Voltage selected on the wattmeter∗Current selected on the wattmeter∗cosΦ Full scale reading of the wattmeter 2.

Power Factor=

W V∗I

3. Power Consumed = V x I x cosΦ RESULTS: 1. Power factor with capacitor = _____________. Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

2. Power factor without capacitor = ____________. 2.b) POWER AND POWER FACTOR MEASUREMENT OF LED , COMPACT FLUORESCENT AND INCANDESCENT LAMPS AIM: To measure power factor of LED, Compact Fluorescent and Incandescent Lamps. APPARATUS REQUIRED: One (0-1A) AC ammeter, one (0-300V) AC voltmeter, one (1/2A, 250V, LPF wattmeter), and connecting wires. CIRCUIT DIAGRAM:

Fig .2.6: Measurement of power of CFL, LED and Incandescent lamps PROCEDURE:

Sl. No

Lamp

1.

LED

2.

CFL

3.

Incandescent Lamp

1. 2. 3. 4. 5. 6. 7.

Voltmeter reading

Ammeter reading

Wattmeter reading

(V) volts

(A) amps

(W * Constant) watts

Power (P)

Power Factor (PF)

Connections are made as shown in the circuit diagram of Fig .2.6. Connect the LED lamp. The Main supply switch is closed and readings of all meters are noted down. Switch OFF the supply and replace the LED lamp with a Compact Fluorescent Lamp (CFL). Again the switch ON supply and note down the readings of all meters. Switch OFF the supply and replace the CFL with an incandescent Lamp. Again the switch ON supply and note down the readings of all meters. Switch off the AC supply mains and remove the connections.

TABULAR COLUMN:

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

CALCULATIONS:

1. Wattmeter Constant : Voltage selected on the wattmeter∗Current selected on the wattmeter∗cosΦ Full scale reading of the wattmeter

2.

Power Factor=

W V∗I

3. Power Absorbed(P) = V x I x CosΦ RESULTS: Power absorbed by incandescent lamp and its power factor: _________. Power absorbed by CFL and its power factor: __________. Power absorbed by LED and its power factor: __________.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

a) OBSERVATION OF THE EXPERIMENT :

b)

TABLE OF EVALUATION : PARTICULARS

MAX.MARKS

Date Sheet

03

Viva

03

Result

04

Total

10

MARKS OBTAINED

Signature of the faculty:

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

EXPERIMENT NO: 03 THEORY : WATTMETER: The wattmeter is an instrument for measuring the electric power which is real power (or the supply rate of electrical energy ) in watts of any given circuit. The device consists of a pair of fixed coils, known as current coils, and a movable coil known as the potential coil. The schematic and image of wattmeter are as shown in Fig 3.1. The current coils are connected in series with the circuit, while the potential coil is connected in parallel. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement. A current flowing through the current coil generates an electromagnetic field around the coil. The strength of this field is proportional to the line current and in phase with it. The potential coil has, as a general rule, a high-value resistor connected in series with it to reduce the current that flows through it. There are two types of wattmeters: i)

Low Power Factor wattmeter(LPF) ii) Unity Power Factor wattmeter(UPF) Low Power Factor wattmeter(LPF) LPF(Low Power Factor) wattmeter is used to measure power in inductive circuits.

Unity Power Factor wattmeter(UPF) UPF (Unity Power Factor) meter measures the PF more accurately when connected to a load which is having a high PF.

UPF Wattmeter

LPF Wattmeter Fig .3.1

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

POWER MEASUREMENT OF BALANCED STAR AND DELTA CONNECTED LOADS AIM: To measure the power consumed by a 3-phase balanced star & delta connected load. APPARATUS REQUIRED: One (0-2A) AC ammeter, one (0-600V) AC voltmeter, three (0-1/2A, 250/300V, UPF wattmeter), one three-phase auto transformer, One resistive load and connecting wires.

CIRCUIT DIAGRAM: a) Two-Wattmeter method for star connected load

Fig . 3.2 : Two-Wattmeter method for star connected balanced load b) Two-Wattmeter method for delta connected load

Fig. 3.3 Two-Wattmeter method for delta connected balanced load.

Dept. of Electrical and Electronics Engineering, R.V. College of Engineering, Bengaluru

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Elements of Engineering Practices Lab Manual & Observation Book

PROCEDURE: 1. Connections are made as shown in the circuit diagram of Fig 3.2. 2. Ensure that the autotransfo...