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BEE Lab Manual

BASIC ELECTRICAL ENGINEERING(FIRST YEAR ENGINEERING)

LAB MANUAL

DEPARTMENT OF ELECTRICAL ENGINEERINGVIDYA PRATISHTHAN’S COLLEGE OF ENGINEERING

BARAMATI.

DEPARTMENT OF ELECTRICAL ENGINEERINGVIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI

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------------------------------------------------------------------------------------------------------------1. A) SAFETY PRECAUTIONS B) ENERGY CONSERVATION------------------------------------------------------------------------------------------------------------

Aim: A) Study of safety precautions while working on electric installations and necessity of earthing.

B) Introduction to energy conservation and simple techniques to achieve it.

A) Safety Precautions:

It is necessary to take some safety precautions while using the electricity to avoid serious problems like shocks and fire hazards.

Some of the safety precautions are listed below:

1. Insulation of the conductors must be proper and in good condition. If it is not so, the current in the conductors may find an alternative path through the body of the person coming in contact with such conductors resulting into an electric shock.

2. Megger tests should be carried out for checking insulation resistance. With the help of a megger, all the tests such as insulation test with respect to earth, insulation test between two conductors, continuity test, test for earth resistance & polarity test for single pole switches must be performed on the new wiring before energizing it for use.

3. Earth connection should always be maintained in proper condition.4. Supply from mains must be switched off and the fuses must be removed before

starting repair or maintenance work on any installation.5. Fuses must have correct ratings. 6. Rubber or plastic-soled shoes or chappals must be used while working on an electrical

installation. Using a wooden support under the feet is advisable as it avoids the contact with the earth.

7. Rubber gloves of appropriate voltage rating should be used while touching the terminals or while removing insulation layer from a conductor.

8. A line tester should be used to check whether a terminal is ‘live’ i.e. holds any potential. More appropriate method is to use a test lamp.

9. Insulated screwdrivers, pliers, line testers etc. should be used.10. Two different terminals should not be touched at the same time.11. The plug should never be removed by pulling the wires connected to it.12. The sockets should be fixed at a height beyond the reach of the children.

Necessity of earthing:

Earthing is very important from safety point of view. The connection of metallic parts of electrical apparatus to general mass of earth, with a wire made of material having high value of conductivity is called as earthing (or grounding). The earth is assumed to be at zero electric potential


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Consider a single-phase machine, which is not earthed as shown in figure 1. The windings and coils inside the frame of machine carry current. Let Ri be the resistance (known as insulation resistance) between the windings and the frame and Rbody be the resistance of the body of a person touching the machine.

d Figure 1

Its equivalent circuit can be drawn as:

Where Im is the current taken by the machine and Ibody is the current passing through the body of the person.

When a person, standing on the earth touches the machine, the current gets an alternative path through the body of the person to earth. From the equivalent circuit

we can write,

Ibody = V_______……(1)

Ri + Rbody + RE

When the insulation of the machine is perfect, the insulation resistance is of the order of few mega ohms and practically can be considered as infinity. So, when Ri = ∞ ……..Insulation is perfect Therefore Ibody = V_______ = 0 ……(2) RE + ∞ + Rbody So in normal operating conditions, there is no current passing through the body of the person and hence there is no danger of the shock.

But when the insulation becomes weak or defective or if one of the windings is touching to the frame directly due to some fault, then R i i.e., insulation resistance becomes almost zero.


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Now resistance of body and earth are not very high and hence Ibody increases to such a high value that the person receives a fatal shock. Such a current is called a leakage current. Hence when the machine is not earthed, there is always a danger of the shock, under certain fault conditions.

Let us see now, what happens due to earthing. In case of earthing, the frame of the machine is earthed as shown in the figure 2 (a).

The resistance of the path from frame to earth (i.e., RE1) is very very low. When the person touches the frame, and if there is a leakage due to fault condition, due to earthing a leakage current takes a low resistance path i.e. path from frame to earth, bypassing the person. So body of the person carries very low current, which is not sufficient to cause any shock.

The equivalent circuit of the earthed condition is shown in the fig 2(b).

When there is a leakage current due to deterioration of insulation, R i approaches to zero. So current is sufficiently high to cause a fatal shock. But at point E shown in the fig. 2 (b) the current IT has two paths.

i. One flowing through Rbody (through the person).ii. Other through new earthing connection having resistance RE1.

The current through the body of the person can be obtained by using the results of current division in a parallel combination.

Ibody = IT x RE1___ ……….(3) Rbody + RE1

Now RE1 is very very small about 1 Ω while Rbody under worst condition is 1000 Ω but generally higher than 1000 Ω. Hence, current Ibody is negligible small compared to current IE1.

So entire leakage current IT passes through the earthing contact bypassing the body of the person. The value of Ibody is not sufficient to cause any shock to the person. Not only this but the current IT, is high due to which fuse blows off and thus it helps to isolate the machine from the electric supply.


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Fig.2 (a)

Fig.2(b)

Use of Earthing: Apart from basic use of earthing discussed above, the other uses can be stated as:

1) To maintain the line voltage constant.2) To protect tall buildings and structures from atmospheric lightening.3) To protect all the machines, fed from overhead lines, from atmospheric lightening.4) To serve as the return conductor for telephone and traction work. In such case, all the

complications in laying a separate wire & the actual cost of the wire, is thus saved.5) To protect the human being from disability or death from shock in case the human

body comes into the contact with the frame of any electrical machinery, appliance or component, which is electrically charged due to leakage current or fault.

B) Energy Conservation

Energy conservation is the practice of decreasing the quantity of energy used. It may be achieved through efficient energy use, in which case energy use is decreased while achieving


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similar outcome, or by reduced consumption of energy service. Energy conservation may result in increase of financial capital, environmental value, national security, personal security and human comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy cost and promote economic security. Industrial and commercial users may want to increase efficiency and thus maximise profit.

Energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capital, and thus offsets the growth in energy supply needed to keep up with population growth. This reduces the rise in energy cost and can reduce the need for new power plants and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred method of energy production.

By reducing emission, energy conservation is an important part of lessening climate change. Energy conservation facilitates the replacement of non-renewable sources with renewable energy sources. Energy conservation is often the most economical solution to energy shortage and is a more environmentally benign alternative to increased energy production

Simple techniques to achieve energy conservation.

To save energy is the need of the hour. Electrical energy conservation is a process comprising of measurement of running load parameters of all individual motors/ devices.

Analyzing the data collected and measured for the possible energy conservation by various methods.

Implementing the recommendation derived from the analysis such as energy audit for achieving positive result.

Based on cost of implementation and the payback period the energy conservation methods may be classified as;

(1) Zero cost method – The payback period is immediate and there is no cost involved for implementing energy conservation by this method. Some of the possible measures to be taken to ascertain the quantum of energy conservation are;

Measurement of the running load parameters of all individual motors available. Measurement of HT & LT incoming and distribution network branch loads. Measurement of incoming and outgoing power transfer load parameter. Study of capacitor distribution for uniform power factor.

In some plants, there are over sized motor during design process to take care of any deviation that may defer from the calculation. Once the plant has commissioned; the over sized motor cause lower efficiency. It is also not practicable to fix all motors to the rated design for high efficiency.


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The higher rated motor can be replaced by smaller capacity motor to achieve saving by increasing the percentage load on the motor and its efficiency. The efficiency can also be improved by tuning the load parameters to the optimum instead of replacing the motor.

(2) Low Cost Method - In this method moderate cost will be incurred to achieve the saving and the pay-back period is less than 2- months. It mainly deals with uniform distribution of capacitors by connecting across motor and re location of capacitor banks for achieving reduction in transmission and distribution losses. Due to capacitor re arrangement the power factor from load end will improve uniformly all over the plant which in turn would reduce the flow of current, thereby minimize the copper losses/heat losses.The low cost is due to relocation of capacitor banks/ modification/ cable layout/ man power cost etc. which can save considerable amount of electrical energy and the pay back period will be less than two months.

(3) Medium cost method –This deals with improvement of power factor by procuring new capacitor to minimize the losses and introduction of various energy saving devices that may be made to suit the requirement of equipment. In this method the cost incurred for the energy conservation will have a pay back period less than a year.

(4) High/Capital Cost Method - In implementing this method; the plant has to procure new devices viz. starters, variable frequency drives, lighting with energy savers, installation of high efficiency motors, replacement of air lift with bucket elevator etc. The pay back period for high/ capital cost method will be more than one year. To streamline all above methods of energy conservation, energy audit is an effective tool.

Energy audit- “A systematic approach to monitor industrial energy consumption and pin-point of wastage of energy is known as energy audit.”

In the present crisis of energy availability and industrial competition, energy auditing has become an important part of any industrial activity. An energy audit helps an organization to understand and analyse its energy utilization and identify areas where energy use can be reduced, decide on how to budget energy use, plan and practise feasible energy conservation methods that will enhance their energy efficiency, curtail energy wastage and substantially reduce energy costs.

The energy audit serves to identify all the energy streams in a facility, qualify energy usage with its discrete functions in an attempt to balance the total energy input with its use. Energy audit is thus the key to a systematic approach for decision making in the area of Energy Management. As a result, energy audit study becomes effective tool in defining and pursuing comprehensive energy management goals.


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An energy audit study includes – Auditing of energy consumption (including any heat or power generated) General examination of work place (including physical condition of organization, its

processes, occupancy time and variation in ambient temperature and energy consumption pattern etc.)

Measuring of all energy flows (including testing of boiler or steam raising, heat equipment, refrigeration etc.)

Analysis and appraisal of energy usage (e.g. specific fuel consumption, energy product interrelationship )

Energy management procedures and methodology Identification of energy improvement opportunities and recommendation for energy

efficiency measures and quantification of implementation costs and paybacks. Identification of possible usages of co-generation, renewable sources of energy and

recommendations for implementation, wherever possible; with cost benefit analysis.

Conclusion:

There is a good potential for reducing power consumption by optimizing the utilization of electrical energy by tuning the load parameters to suit the requirement. Every unit saved is a unit generated. Looking to the substantial capital involved in the generation and transmission of energy, it is necessary to reduce losses of every kind to the best possible extent by making Energy Audit a routine rather than a one time expensive. Energy conservation is a sacred objective since it results in achieving increased long lasting resources of energy apart from the reduction in production cost. Minimizing the wastage is a continuous process, in which cumulative efforts are involved for bringing down specific power consumption levels lower and lower.


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------------------------------------------------------------------------------------------------------------2. WIRING EXERCISE------------------------------------------------------------------------------------------------------------

Aim: - To study various wiring components, control of two lamps from two switches, Staircase wiring and use of megger

Part A: Study of various wiring components (wires, switches, fuses, sockets, plugs,

Lamp holders, lamps etc. their uses and ratings)

WIRES : Types of wires: The various types of wires that are used for various wiring schemes are:

1) Vulcanized India Rubber wires (V.I.R)2) Cab Tyre Sheathed wires (C.T.S)3) Poly Vinyl Chloride wires (P.V.C)4) Flexible wires5) Cables

V.I.R. (Vulcanized India Rubber) Wires This type of wire consists of tinned conductor coated with rubber insulation. This is further covered with protective cotton and bitumen compound and finally finished with wax. This makes it moisture and heat resistant. These are always single core wires. As they are covered with a cotton layer, they have a tendency to absorb moisture and hence rarely used now a days.

C.T.S. (Cab Tyre Sheathed) WiresIn this type, ordinary rubber insulated conductors are provided with an additional tough rubber sheath. The wire is also known as Tough Rubber Sheathed (T.R.S) wire. It provides additional insulation and also protection against moisture, chemical fumes and wear and tear. They are available in single core, double core and three core varieties.

P.V.C. (Poly Vinyl Chloride) Wires

These wires, which are most commonly used, have conductors with P.V.C. insulation. P.V.C. is non-hygroscopic, tough, durable, corrosion resistant and chemically inert; therefore, it is suitable for general wiring work. P.V.C. insulation, being sufficiently tough to give mechanical protection, cotton taping or braiding is not essential as in the case of ordinary


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Conductor

Insulation

Lead Sheath

Bedding

Armoring

Serving

General Construction of the Cable

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rubber insulated conductors. P.V.C. being a thermoplastic, softens at high temperatures. Therefore, it should not be used where, extreme temperatures are


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likely to occur. For example, it should not be used for making connections to heating appliances.

Flexible Wires

Theses are used very commonly in domestic wiring or for wiring of temporary nature. It consists of two separately insulated stranded conductors. The insulation is mostly made of rubber. They are more commonly available in parallel or twisted twins. Due to its flexible nature, the handling of these wires becomes very easy.

CABLES:

Types of cables: There are two types of cables available:

a) Aerial cables

b) Underground cables

A cable can be defined as a group of individually insulated conductors, which is put together and finally provided, with a number of layers of insulation to give mechanical support. The figure shows a general construction of an underground cable.

Conductor or core: This consists of stranded aluminium or copper conductors.

Insulation: Commonly used insulating material is impregnated paper, vulcanized bitumen.

Metallic sheath: This is an aluminium sheath or lead sheath, which covers the insulation and provides mechanical protection. It restricts moisture to reach to the insulation.

Bedding: It consists of some fibrous material, which protects metallic sheath from corrosion

Armouring: This consists of layers of galvanized steel wires, which provide protection to the cable from mechanical injury.

Serving: It is a layer of fibrous material like jute cloth, which protects the armouring from atmospheric conditions.

As in cities and big towns the network of the aerial cables or overhead wires is not feasible, it is necessary to use the network of the underground cables.

The cable with only one conductor is called as a single core cable. The cable with two conductors is called as a two core cable and so on.

Specification of wires:

Similar to the cables, many other types of wires also use more than one conductor in them. The wires using more than one strand of conductors in them are called as multistranded wires. The number of strands in various types of wires are 3, 7, 19, 37, 61, 91, 127 and 169. This number of strands ensures that the cross-section of the conductor or wire remains circular in shape.

The multi-stranded construction increases the current carrying capacity of the wires. As current through conductor increases, heat produced is more. In case of single solid conductor, majority of current flows near the surface and hence surface becomes very hot and


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insulation comes under high temperature stress. Due to many strands, the current gets divided into number of paths and larger surface area is available for heat dissipation than the single solid conductor. Hence, for the same temperature limit, a multistranded wire can carry more current than single solid conductor. A multistranded wire is more flexible as the cross section of each strand is much less. It makes it suitable while wiring. If at all there is an open circuit in one of the strands, other strands can carry current. The heat produced gets dissipated quicker in multistranded wires.

The one way of specifying wires is the number of strands of conductors used in it. Secondly, various insulations can withstand different temperatures and depending upon the type of insulation, wires are specified. As mentioned earlier, various insulations are vulcanized India rubber, cab tyre, tough rubber, and poly vinyl chloride etc. So wires are specified as V.I.R., T.R.S., C.T.S., and P.V.C. wires. Now a days, P.V.C. insulated wires are very commonly used.

The size of the strand of the conductor is also important from the specification point of view. The size determines the current carrying capacity of the conductor. To specify the size of conductor various methods, are used.

SWITCHES:

The switch is a device, which is used to make (close) or break (open) the electrical circuit. At the instant of breaking, the switch should not produce an arc at the contacts of the switch. To ensure fast switching, switches are provided with a spring to its movable blades. The various types of switches are shown in the figure.

S.P.S.T. (Single pole single throw) switch: It consists of only one pole and it can be thrown only on one side for making or breaking the circuit.

S.P.D.T. (Single pole double throw) switch: This is further classified as a two-way switch or a two way with center off switch. A two-way switch always makes contact with one of the two poles and a two way with center off switch can be kept at its center position keeping away from the two poles.

D.P.S.T. (Double pole single throw) switch: For simultaneous action of both poles, a spring is provided connecting two movable blades.

D.P.D.T. (Double pole double throw) switch: This is also available in the form of intermediate switch.T.P.S.T. (Triple pole single throw) switch: This is used for three-phase supply. Other varieties of switches are push button switch, rotary snap switch, flush switch etc.


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FUSES:When there is short circuit, overload or some type of fault in the circuit, heavy current

flows through it. This is dangerous to the appliances connected to the same supply and also to the loads connected in parallel to the same line. High current overheats the wires and damages the insulation. Hence, under such conditions, it is necessary to break the supply. This is done by a fuse.

a) Semi-enclosed or Rewirable Type Fuse:

It consists of a porcelain base and a wire, which melts at higher temperatures. It is inserted in live or phase wire. When current exceeds certain limit, fuse wire melts due to overheat and supply to the circuit gets disconnected. Either copper or lead-tin alloy is generally used as a fuse wire. Instead of connecting the fuse wire directly in series with live wire, a fuse top is used which is having porcelain base. The porcelain structure containing fuse wire is bridged to the base by fitting top into the base. Such arrangement is called as kitkat type of fuse unit.

Advantages:

They are cheaper. After blowing off the fuse element, the bridge can be pulled out and again rewired

with a new fuse wire. Thus, service can be restored very quickly with negligible additional expenditure.

Disadvantages:

Cannot be used for higher values of fault current. Protection is not reliable due to inaccurate characteristics. Since the wire is exposed to air, it is subjected to deterioration due to oxidation caused

by heating. This decreases the effective diameter of the wire. Heating due to increased resistance causes premature failure under normal load.

Slow speed i.e. current interruption is not quick in comparison with other interrupting devices.

Risk of fire-hazards due to external flash on blowing.

Applications: Commonly used in domestic installations and other circuits where very low values of fault currents are to be handled.

b) HRC Fuse:

This fuse is used to break the circuit where fault current level is very high. In such cases, the fuse has to withstand heavy stresses hence the construction is of totally closed type. This type of fuse is called as high rupturing capacity (H.R.C.) fuse. The fuse wire is enclosed in a ceramic cartridge. The ends of fuse wire are connected to metal caps. The body of cartridge is filled with powdered quartz. When fuse melts, it reacts with quartz powder forming a substance having high resistance like insulator. This also restricts the arc formation.


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Advantages:

Being totally closed, there is no deterioration of the fuse element. Due to accurate characteristics and consistent performance, protection is reliable. High-speed operation. Ability to clear high values of fault current. Its operation is silent and without flame, gas or smoke. Hence safe from the point of

view of fire hazards.

Disadvantages:

Costly in comparison with Rewirable type fuses. The fuse is to be totally replaced by a new one after each operation. Overheating of the adjacent contacts is possible during the operation of the fuse.

Applications:With the increasing loads and sizes of the networks, H.R.C. cartridge fuses are now gradually replacing the rewirable types, particularly in industrial installations. They are also frequently used in low voltage distribution systems. LAMP HOLDERS:

These are used to hold the lamps required for lighting purposes. These are made up of brass, bakelite or hard plastic. The lamp holders are classified as, having moulded or porcelain interior with a solid plunger and having moulded interior with spring plunger.The two types of holders are bayonet type and screw type holders. Each of these types is further classified into the following types.

Batten holders:These can be screwed to wooden blocks and hence can be used for wall or ceiling attachments. Pendant holders: These can be used for lamps hanging from the ceiling.Bracket holders: These can be screwed on a wall bracket or on a table lamp stand.

PLUGS & SOCKETS:

The sockets have insulated base having two or three sleeves. These are the points from which electricity can be tapped. In two terminal socket, the terminals are phase and neutral but in case of a three terminal socket, two thin terminal sleeves are for phase and neutral while the third of thicker cross-section is meant for earth connection. For tapping power from the socket, 2 or 3 pin plug is used. By using socket and plug, the various domestic appliances can be connected to an electric supply. Both three-pin and two-pin type plugs and sockets are available with the rating of 5 A - 250 V & 15 A - 250 V


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Part B: Control of two lamps from two switches (looping in system):

Equipment required:

Single Pole switches: 2 Nos.Connecting wires Bulbs (40 Watt) : 2 Nos.

Working: This type of wiring is called as a looping in system. Instead of running separate wires for each lamp from the supply point, they are looped in from one lamp to other. In this case it will be observed that the position of any switch does not affect the working of the other lamps, and thus its own switch controls each lamp independently.

Application: This system is commonly used in domestic wiring as it saves length of wire & avoids the soldered joints.


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Part C: Staircase wiring:

Equipments required:Two-way switches: 2 Nos.Bulbs (40 Watt): 1 No.Connecting wires

Working: When a person has to climb stairs, the staircase needs to be illuminated. For this purpose switch S1 is kept in position ‘b’ (switch S2 is in position ‘b’) so that the circuit is completed and bulb lights up. After climbing the stairs, one does not need the light any more, so switch S2 is brought to position a, the circuit breaks and lamp is switched off. While coming down, switch S2 is brought to position b to put the lamp on. After reaching downstairs, switch S1 is put in position ‘a’ to put off the lamp. Thus two switches can control one and the same lamp.

Application: Normally used for staircases and corridors.

Part D: Use of megger for insulation test & continuity test of wiring installations & machines.

Objectives: To get familiar with use of megger for insulation test and continuity of installation and machines.

Equipment: Megger ---- 1 No.

Megger is used for measurement of high resistance (of the order of Mega-Ohm). That is why it is called as megger. To avoid the shock, insulation resistance of the installation should be very high. This resistance can be measured with the help of megger. Before any electrical installation is connected to supply for the first time, certain tests have to be carried out to ensure that there is no leakage, which may cause danger.

Testing of electrical installation: Before any electrical installation is connected to supply, number of tests have to be carried out to ensure that there are no defects, which may cause danger. The following test should be conducted before a new electrical installation is put into service.

Testing insulation resistance: For testing insulation of the installation, we have to check insulation resistance between earth & conductor and the insulation resistance between conductors.

(A) Insulation resistance between earth & conductor: For the purpose of safety, it is necessary to ensure that there is no leakage current through the insulation used. This test gives the value of the insulation resistance between earth & conductor. Insulation resistance can be measured with the help of 500 V megger using the procedure as given below.

Keep all fuse links, all switches and lamps in position. The main switch should be off. Connect the line terminal of megger to either of the main leads (phase or neutral) and

earth terminal to any point on the earth continuity conductor of the system. Rotate the handle of megger with hand and note down insulation resistance between

conductor and earth. This resistance should not be less than 50 M-Ohm divided by the number of outlets.


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(B) Insulation resistance between conductors:

In this test, keep all the switches and fuse links in position. Keep the main switch in off position. Remove all the lamps and appliances from supply.

Now connect the megger terminals between two conductors (phase & neutral). Rotate the handle of megger with hand & note down insulation resistance between

conductors. This resistance should be less than specified in previous test.

Observation Table:

Sr. No. Insulation resistance between earth and conductor

Insulation resistance between conductors

(C) Insulation Test on machine:

Keep all the switches and fuse links in position. Keep the main switch in off position. Now connect the megger terminals between machine winding and the frame, also

between the two windings. Rotate the handle of the megger with hand and note down the insulation resistance

between windings and frame and between the two windings

Observation Table:

Sr. No. Insulation resistance between winding and frame

Insulation resistance between two windings


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TITLE OF EXPERIMENT :- ________________________________________

__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________

BATCH: ______________________ ROLL NO.: ______________________

PERFORMED ON DATE: ___________________________________________

SIGN. OF TEACHING STAFF WITH DATE:___________________________

------------------------------------------------------------------------------------------------------------STUDY OF LAMPS

------------------------------------------------------------------------------------------------------------

Aim: A) Study of fluorescent tube circuit

B) Study of Compact Fluorescent Lamp (CFL)

C) Study of Mercury Vapour Lamp & Sodium Vapour Lamp.


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PART (A): Study of fluorescent tube circuit

CONSTRUCTION: The fluorescent tube is a low-pressure mercury discharge lamp. It generally consists of a long glass tube (G) with an electrode at each end. These electrodes are made of tungsten filament coated with an electron emitting material. The tube is coated from inside with a fluorescent powder and contains a small amount of argon together with a little mercury at a very low pressure. The control circuit of the tube consists of a starting switch (S) known as a starter, an iron cored inductive coil called a choke (L) and two capacitors (C1 and C2).

OPERATION: Two types of starters, namely; the glow type (a voltage operated device) and the thermal type (a current operated device) are generally used. A tube fitted with a glow type starter (S) is shown in figure. This starter consists of two electrodes hermetically sealed in a glass bulb fixed with a mixture of helium and hydrogen. One electrode is fixed and other is a U-shaped bimetallic strip made of two metals having different temperature coefficients of expansion. The contacts are normally open. When the supply is switched on, heat produced due to glow discharge between electrodes of starter is sufficient to bend the bimetallic strip (due to expansion of two metals) until it makes contact with the fixed electrode. Thus the circuit between two electrodes is completed and a relatively large current flows through them. The electrodes are heated to incandescence by this circulating current and the gas through their immediate vicinity is ionized. After a second or two, due to the absence of glow discharge, which ceases after the closing of the contacts of the starting switch, the bimetallic strip cools sufficiently. This causes it to break contacts and the sudden reduction of current induces an e.m.f. of about 800-1000 V in the choke coil. This voltage is sufficient to strike an arc between the two electrodes due to ionization of argon. The heat generated vaporizes the mercury and the potential difference across the tube falls to about 100-110 V. This potential difference is not sufficient to restart the glow in starter.


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COMPACT FLUORESCENT LAMP

For a thermal type starter, the circuit arrangement is as shown in figure. This switch (S) is either open type or enclosed in a hydrogen filled gas bulb. It has a bimetallic strip close to a heater element (R). The two elements of starter are normally closed. Consequently, when lamp is switched on, the circuit being complete through the thermal switch, a relatively large


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current flows through the two filaments of the tube. This circulating current heats the filaments to the incandescence and the gas in their immediate vicinity is ionized. Since the same current is also passing through the heater element (R), it causes the bimetallic strip to break contact and the inductive voltage surge due to the choke starts the discharge in the tube. The starter contacts then remain open till the lamp is in operation due to the heat generated in the heater element.

PART B:

Study of Compact Fluorescent Lamp (CFL)

Introduction:

The increasing popularity of energy efficient lamp has led to a virtual explosion of new lamps and ballasts. Compact fluorescent lamps (CFL) are the energy efficient lamp and used as alternative to incandescent lamps. They consume as little as 1/5 th of power and also have long life. The increasing varieties in shape, colour and size have made them more versatile and acceptable than the traditional fluorescent lamps.

CONSTRUCTION

A CFL consist of a gas filled glass tube with two electrodes mounted in an end cap. It contains a low pressure mix of argon gas, mercury and is a coated on the inside with three different phosphors. The electrode provides a stream of electrons to the lamp and ballast control the current and voltage. Ballast may be attached directly to the lamp or may be remotely connected. The main parts of any CFL is the ballast. The ballast provide the high initial voltage required to create the starting arc and then limits current to prevent the lamp from self destructing

OPERATION:

The visible light from CF lamp is produced by a mixture of three phosphors on the inside of the lamp. They give a off light when exposed to ultraviolet radiation released by mercury atoms as they are bombarded by electrons. The flow of electron is produced by an arc between two electrodes at the ends of the tube.

COLOUR:

1) When single phosphors coating is used inside the lamp it produce a cool white light.


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2) when three phosphors coating is use inside the lamp it produce light in the red, blue and green regions of the visible spectrum, giving white light when blended together.

PART C:


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1) Study of Mercury Vapour Lamp

THEORY: There are different types of high-pressure mercury vapour lamps available in a range of 80W, 125W, 250W & 400W. The high-pressure lamps are used either for street lighting or for industrial purposes.

CONSTRUCTION: It consists of a glass tube of borosilicate, which is quite hard. At the ends of the tube, two electrodes made of specially coated wires are provided. Near the upper electrode, there is one more auxiliary starting electrode, which is connected to the bottom electrode through a high resistance. The tube is sealed with an inside pressure of 1 & 1/2 atmosphere. This tube is further enveloped by another tube; the advantage being that, the heat of inner tube is not dissipated & the tube does not come in contact with sudden changes in temperature. The lamp has a screwed cap & is connected to the mains supply through a choke. To improve the power factor, a condenser is connected across the mains as shown. The inner tube; in addition to mercury; also contains a small quantity of argon since, at the time of starting the tube is cold & the mercury is in the condensed form.

OPERATION: When the tube is switched on, an arc between main electrode & auxiliary electrode discharges argon. Due to the high resistance, the discharge shifts between two main electrodes. The heat produced during discharge warms up the tube & the mercury is evaporated & the pressure inside grows. The discharge later takes up the shape of intense arc. After about 5 minutes the lamp starts giving full brightness. The choke stabilizes the discharge i.e., limits the current to a safe value.

APPLICATIONS: These lamps are widely used for outdoor yard lighting & street lighting.

ADVANTAGES: Efficiency more than that of a filament lamp. Hence, gives more light output per input Watt. Longer life (about 3000 working hours)

DISADVANTAGES: Requires warming up time of about 3 to 5 minutes. If the lamp goes out while in service, for its restarting cooling is

necessary.


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2) Study of Sodium Vapour Lamp

THEORY: The different ranges of sodium vapour lamps are 70W, 125W, 250W, 400W. The colour of sodium discharge lamp is bright yellow & is recommended only for street lighting.


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CONSTRUCTION: The sodium vapour lamp is similar in construction to the mercury vapour lamp. The glass of this tube is also special since sodium vapour blackens the ordinary glass. The lamp is quite sensitive to temperature so to keep the temperature of the lamp within working range, it is enclosed in a double walled flask. In addition to sodium small quantity of inert neon gas is also inserted.

OPERATION: Before the lamp starts working, the sodium is usually in the form of a solid deposited on the sides of tube walls. So in the initial stage when the potential is applied to the lamp, it operates like low pressure neon lamp with pink colour, but as the lamp warms up it vaporizes sodium & slowly radiates out yellow light & after about twenty minutes the lamp starts giving its full output.

IGNITOR:At the time of starting of the discharge lamp, a voltage higher than normal supply voltage is required. Such voltages are obtained from a transformer. The transformer used has a very poor regulation i.e. at no load when no current is taken from the transformer the voltage is very much higher than when the transformer is loaded. Thus when the discharge starts the output voltage of transformer falls. Hence the transformer acts as a blast or ignitor

APPLICATION: The colour of the sodium discharge lamp is bright yellow & is used for the illuminations of the roads, goods yards, airports etc. They are also sometimes used for advertisement purpose.

ADVANTAGES: Highest efficiency, about 3 to 4 times that of the filament lamps. Most of the radiation is on visible region & therefore more economical. Longer life.

DISADVANTAGES:Bright yellow colour is not suitable for indoor lighting. Long tubes are required for sufficient light output. Requires 10 to 20 minutes for giving full output. Since the sodium solidifies when the tube cools, it is necessary to ensure that the sodium is deposited reasonably uniformly along the whole length of the tube & not concentrated at one end. Consequently the lamp is to be used preferably in a horizontal position.


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BEE Lab Manual


__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________

BATCH: ______________________ ROLL NO.: ______________________




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ELECTRICAL ENGINEERING DEPARTMENT

VIDYA PRATISHTHAN’S COLLEGE OF ENGINEERING

------------------------------------------------------------------------------------------------------------


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EFFECT OF RISE IN TEMPERATURE ON RESISTANCE OF MATERIAL------------------------------------------------------------------------------------------------------------

Aim: To study the effect of rise in temperature on the resistance of a conducting material.

Apparatus: 1. DC Ammeter --- (0-1 A)2. DC Voltmeter --- (0-300 V)3. Rheostat --- (570 , 1.2 A)4. Stop watch5. Field winding of DC machine as a conducting material.

Theory:

When the temperature of a conductor is changed, the change in resistance depends on following factors:

1. Its initial resistance.2. The rise in temperature.3. The nature of the material of the conductor.

i.e. Rt2 – Rt1 Rt1 (t2-t1)

OR

Rt2 – Rt1 = t1 Rt1 (t2-t1)

Where, t1 = temperature coefficient of resistance of the conductor at initial temperature. Rt2 = resistance of the conductor at t 0c. Rt1 = resistance of the conductor at initial temperature. t2-t1 = change in température.

Procedure:

1. Make the connection as per circuit diagram.2. Keep the rheostat in intermediate position.3. Switch on DC supply. 4. Note down voltmeter and ammeter reading.5. After 5 minutes again adjust current to the constant value with the help of

rheostat & take down voltmeter reading.6. Repeat the procedure after every 5 minutes& take down 6 reading.7. Plot the graph of resistance Vs temperature.

Observation Table:


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Sample

Calculation:

1) Assume, Initial temperature as 250C2) Resistance at 250C i.e. initial resistance

Rt 1=Voltage at 250CCons tan t Current

3) Temperature Coefficient of resistance of copper at 00C i.e. 4) Temperature Coefficient of resistance of copper at 25 0C i.e. 25

α 1 =α25 = 1

(1α0

+25 )

Rt 2 =Voltage at t

0CCurrent ( I )

Rt2 - Rt1 = 1 Rt1 (t2 – t 1)

5) Calculate t 2 for each reading.


Sr.No.Time

(Minutes)Voltage across winding

(Volts)Current(Amp.)

1 0

2 5

3 10

4 15

5 20

6 25

7 30

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BEE Lab Manual

Result Table:-

Graph: Plot a graph of

Temperature versus Resistance

Conclusion:As temperature of coil increases, its resistance goes on increasing. Hence copper has a positive temperature coefficient of resistance.


Sr.No.Resistance

(ohm)Temperature (t2)

( 0 C)1234567

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TITLE OF EXPERIMENT: ________________________________________

__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________

BATCH: ______________________ ROLL NO.: ______________________




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ELECTRICAL ENGINEERING DEPARTMENTVIDYA PRATISHTHAN’S COLLEGE OF ENGINEERING

------------------------------------------------------------------------------------------------------------THEVENIN’S THEOREM

------------------------------------------------------------------------------------------------------------

Aim: To verify Thevenin’s theorem

Apparatus: 1. Experimental kit.2. Dual power supply (0-30 V D.C., 2 A, CC/CV) 3. D.C. milliammeter (0-500mA)4. Multimeter5. Connecting wires


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Theory: Thevenin’s theorem states that, any linear, two port circuit consisting of voltage sources and resistances can be replaced by an equivalent two port circuit consisting of a single voltage source (VTH) in series with a single resistance (RTH), where, the value of ‘VTH’ is equal to the open circuit voltage across the two ports and the value of ‘RTH’ is equal to the net resistance of the entire circuit across the same two ports.

‘VTH’ and ‘RTH’ are called as Thevenin’s equivalent voltage and resistance respectively.

This idea can be used to find current in any circuit element (or to find voltage across any circuit element) say, a resistor. Let us find the current in a certain resistor in the given circuit. We call this resistor as the ‘load resistor (RL)’.

First, we assume that this resistor is removed from its place. The remaining circuit will be a two-port circuit as shown to left hand side in above diagram. Then we measure the voltage between the two ports and also the effective resistance of the entire circuit across the same two ports with suitable methods. Finally we represent the given circuit with Thevenin’s equivalent circuit as shown to right hand side in the above diagram.

When we replace the load resistor across the same two ports, the given circuit will be equivalent to a circuit as shown in the adjacent diagram. Hence, the current in the load resistor will be;

I =

V THRTH+R L

Procedure: 1. Apply certain voltages from the two voltage sources. Observe and note down the

current in the load resistor (as shown by the ammeter connected in series with it. This reading is required to compare the results i.e., for verification of Thevenin’s theorem).

2. Now, remove the load resistor (RL) through which the current is to be determined. 3. Measure the voltage between the two terminals from where the load resistance has

been removed. This is the value of Thevenin voltage ‘VTH’.


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4. Now, short-circuit the voltage sources (assuming the voltage sources to be ideal). Measure the resistance of the whole network between the same two terminals with the help of multimeter. This is the value of Thevenin resistance ‘RTH’.

5. Repeat the procedure for a different set of source voltages and record all the observations as before.

Observation Table:

R1 = R2 = R3 = R4 = RL =

Obs. No.

Source Voltage

‘V1’

Source Voltage

‘V2’

RL Current recorded by ammeter (IL)

VTH RTH

1

2

Calculation:

Current in load resistor by Thevenin’s Theorem (I’L)=

V THRTH+R L


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BEE Lab Manual

Result table:

Sr. No. IL I’L

1

2

Conclusion:

From the result table it is seen that the actual value of load current IL & the value of load current calculated using Thevenin’s theorem are approximately same. The difference may be due to:

i) Assuming the voltage sources to be idealii) Instrumental errorsiii) Manual errors


__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________

BATCH: ______________________ ROLL NO.: ______________________




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------------------------------------------------------------------------------------------------------------R-L-C SERIES CIRCUIT

------------------------------------------------------------------------------------------------------------

AIM : To study R-L-C series circuit.


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APPARATUS:1) R-L-C series circuit (with variable resistor) -- 1 No 2) A.C. Ammeter (0 - 1A) -- 1 No3) Digital Multimeter / AC Voltmeter (0-300V) -- 1 No

THEORY:Consider a circuit in which a rheostat (which is a variable resistor), an inductor & a capacitor are connected in series. Let a sinusoidal alternating voltage (v) be applied across the circuit. Hence, v = Vm sin ωt

Also, I=VZ

‘Z ’ is known as impedance of the circuit. It is given as; Z=R+ j(XL−X C ) .

The magnitude of impedance is given as; Z = √R2+( XL−XC)2

Where, XL = Inductive reactance = 2L Ohm ( ‘L’ is in Henry)

XC = Capacitive reactance =

12π fC Ohm (‘C’ is in Farad)

Inductive reactance and the capacitive reactance are the oppositions offered to the current due to inductance and capacitance of the circuit.In a series R-L-C circuit, if XL XC, circuit becomes inductive circuit & if XC XL, circuit becomes capacitive circuit.

Power factor: It is the factor, which decides the conversion of input power (or energy) into useful output. It is expressed as the ratio of resistance to impedance of the circuit. It is also defined as the cosine of the angle of phase difference () between applied voltage & resulting current in a circuit.

Power factor (P. F.) =

RZ = cos

PROCEDURE:1) Connect the circuit as shown in the diagram.2) With the help of rheostat, vary the current in circuit.3) For each current setting, read and note down VR, VL, VC, VR-L, and VT with the help of

multimeter.

OBSERVATION TABLE:

SR.NO. I(Ampere)

VR

(Volt)VL

(Volt)VC

(Volt)VR-L

(Volt)VT

(Volt) 1

2

3

CALCULATIONS:


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A) PARAMETERS : i) R =

V RI

ii) XL =

V L sinφLI

iii) XC =

V C sinφCI

iv) L =

X L2πf Henry

v) C =

12π fXC Farad

B) POWERS: i) PR = VR I = I2 R = _________________Watt ii) PL = VL I cos L = __________________Watt iii) PC = VC I cos c = __________________Watt iv) PT = VT I cos T = __________________Watt

Verify that, PT = PR + PL +PC

C) POWER FACTORS: i) P.F of coil = cos L = ____________________ ii) P.F of capacitor = cos c = ________________

iii) P.F. of the entire circuit = cos T = ____________.Procedure for plotting phasor diagram:

1) Current I should be taken as reference phasor,2) Choose a suitable scale for voltage.3) VR (OA) should be drawn in phase with current.4) With ‘A’ as center & radius equal to VL, an arc is drawn. Similarly with ‘O’ as center

& radius equal to VR-L another arc is drawn to cut the first arc at B. Join AB & OB.5) With ‘O’ as center & radius equal to VT , an arc is drawn.6) With ‘B’ as center & radius equal to Vc, an arc is drawn to cut the above arc at C.

Join BC & OC.7) The angles L, C and T are measured.


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BEE Lab Manual

RESULT TABLE:

Obs.No.

R(Ω)

L(H)

C(F)

cosL cosC cosT PR

(W)PL

(W)PC

(W)PT

(W)1

2

3

PHASOR DIAGRAMS: Draw phasor diagrams for all the readings

CONCLUSION:


__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________


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BATCH: ______________________ ROLL NO.: ______________________




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------------------------------------------------------------------------------------------------------------STAR & DELTA CONNECTIONS

------------------------------------------------------------------------------------------------------------

Aim: To study the line voltage-phase voltage & line current-phase current relationships in balanced STAR & DELTA connected loads.

Apparatus:

1) Three phase lamp load --- (440V, 10 Amp.)2) A.C.Voltmeter --- (0-300V-600V) 3) A.C. Ammeter --- (0-5A)4) A.C. Ammeter --- (0-10A)

Theory:A balanced three phase system is one in which the voltages in all phases are equal in magnitude & differ in phase from one another by equal angle i.e.120 degree (electrical). A three phase balanced load is that in which the loads connected across three phases are identical in nature and magnitude.

STAR CONNECTION:

In this type of interconnection, one of the ends of each load impedances are joined together to form a common point called as star or neutral point. The potential difference between line & neutral is called as phase voltage & between two lines is called line voltage.

Hence VRN,VYN,VBN (Each equal to VPH ) are the three phase voltages.

We have, as phasor relations:

V RY=V RN+ V NY = V RN - V YN


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V YB=V YN+ V NB = V YN - V BN

V BR=V BN+ V NR = V BN - V RN

From phasor diagram,

V RY= 2 ×V RN× cos 30 =√3 V RN

i.e., Also IR, IY, IB are the three line currents, as well as the three phase currents

i.e., IL=IPH


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DELTA CONNECTION:

In this type of interconnection, the end of first load impedance is connected to start of second load impedance, the end of second load impedance is connected to start of third load impedance and end of third is connected to start of first. In this way a closed loop of three impedances is formed. Three-phase supply is given to the three junctions in the closed loop of the impedances. Current flowing through any line is called line current (i.e., IR = IY = IB = IL ) & current through any single load impedance is called as phase current (i.e., IRY = IYB =IBR = IPH ). The line voltages VRY , VYB & VBR are phase voltages as well as line voltages.

We have, as phasor relations,IR=I RY - IBRIY=IYB - IRYIB=IBR - IYB

From phasor diagram,

IR= 2 ×IRY× cos 30 =√3 IRY

i.e., IL= √3 I PH

Procedure:

1) Connect the given lamp load in STAR, make it balance by switching appropriate number of lamps in each phase. Measure the line and phase voltages as well as line and phase currents

2) Repeat the same procedure by connecting the load in DELTA.

Observation table:

Connection Line VoltageVL (Volt)

Phase Voltage VP (Volt)

Line CurrentIL (Amp)

Phase CurrentIP (Amp)

STAR1

2

DELTA1

2


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CALCULATIONS:

PHASOR DIAGRAM: Draw phasor diagram to the scale for one case each for star and delta

CONCLUSION:


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__________________________________________________________________

DIVISION : ___________________ BRANCH: _______________________

BATCH: ______________________ ROLL NO.: ______________________




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------------------------------------------------------------------------------------------------------------SINGLE PHASE TRANSFORMER

------------------------------------------------------------------------------------------------------------

PART A) VOLTAGE RATIO & CURRENT RATIO:

AIM: To determine voltage ratio & current ratio of a single phase transformer.

APPARATUS:


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1) Single phase transformer (230/115V) -- 1 No. 2) Dimmerstat (230/0-270V,15 A) -- 1 No.

3) A.C. Voltmeters (0-150-300V) -- 2 Nos. 4) A.C Ammeters (0-5A) -- 2 Nos.

THEORY : A transformer is a static device which transfers electrical energy from one circuit to another without change in frequency. While doing this, it can change voltage and current levels in the two circuits which is decided by the number of turns of the two windings. If N1 & N2 are the number of turns of primary and secondary windings respectively, then;

2

1N

N

is called as the ‘turns ratio’.For ideal transformer the power equation is;

V1 I1 = V2 I2 ………….Eqn I Where, V1 = Primary voltage I1 = Primary current V2 = Secondary voltage I2 = Secondary current

Also, the primary MMF is equal to secondary MMF

i.e., N1 I1= N2 I2 …………….Eqn. II

From equations I & II,

V 2

V 1

=I 1

I 2

=N2

N1

=k

The ratio ‘k’ is called as the ‘transformation ratio’.

The ratio

V 2

V 1

=I 1

I 2

=N2

N1

=k is called as the ‘voltage ratio’

The ratio

V 2

V 1

=I 1

I 2

=N2

N1

=k is called as the ‘current ratio’

PROCEDURE:

VOLTAGE RATIO TEST:

1) Make the connections as shown in diagram. 2) Set the dimmerstat to zero position. 3) Increase the primary voltage in steps of 50 Volt upto rated voltage.

4) Note down the corresponding secondary voltages.


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CURRENT RATIO TEST:

1) Make the connections as shown in diagram.2) Set the dimmerstat to zero position. Apply a very small voltage on

primary side such that certain current (e.g. 1A) flows through primary. Note down corresponding secondary current (I2).

3) Increase the primary current in suitable steps (e.g. each step of 1A) & note down the corresponding secondary currents.

OBSERVATION TABLES:

VOLTAGE RATIO TEST:

Sr.No. V1 (Volt) V2 (Volt) Voltage Ratio= V1/V2

1 0

2 50

3 100

4 200

5 230

CURRENT RATIO TEST:

Sr.No. I1 (Amp) I2 (Amp) Current Ratio= I1/I2

1 0

2 2

3 3

4 4

5

RESULTS: 1) The transformation ratio is________.2) The voltage ratio is _________.


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3) The current ratio is ________.

PRECAUTION:In both the tests, keep dimmerstat to its zero position initially.

CONCLUSION:

From this experiment we can conclude that, the transformation ratio k V2/V1 I1/I2


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PART B) EFFICIENCY AND REGULATION BY DIRECT LOADING METHOD.

Aim: To determine efficiency and regulation by direct loading.

Apparatus:1. Single PhaseTransformer --- 1 kVA, 230/230 V2. A. C.Voltmeter --- (0-300V)3. A. C.Ammeter --- (0-5A) 4. Dimmer stat --- 230V/0-270V, 15A5. Single Phase Lamp bank (Resistive load) --- (230V, 10Amp.)6. Wattmeter --- (5 /10 Amp. , 300 V)

Theory:

Transformer transforms electrical energy from one circuit to another. By keeping primary side voltage constant if load on secondary side is increased, then terminal voltage V2 across the load changes. For a resistive or inductive type of load this change is on negative side, i.e., the terminal voltage drops. With the further increase in load it drops further because the load current increases and hence the voltage drops in resistance and leakage reactance of the secondary winding also increases.

Voltage Regulation:The change in secondary voltage from no load to full load expressed as the fraction of no load secondary voltage is defined as the voltage regulation of transformer.

Losses: There are two types of losses in transformer

1. Copper losses or Winding losses (They are variable).2. Iron losses or Core losses (They are constant)


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Due to various losses, the power output of the transformer is always less than the corresponding power input. So for same input, higher the value of power output i.e. lesser the losses, more efficient is the transformer.

Efficiency: Efficiency of the transformer is defined as the ratio of output power to the input power. When expressed in percentage;

% = (Output power / input power) x 100.

Procedure:

1) Connect the circuit as shown in diagram.2) Initially keep all the lamps off and keep the dimmerstat at zero position. Switch on the

supply and by varying the dimmerstat, apply rated voltage to primary. Note down the readings of currents, voltages and power. The secondary voltmeter reading is obviously the no load secondary voltage V2(0).

3) Now keeping primary voltage constant, increase the load on secondary side in steps by switching the lamps on. Note down various quantities V 1, I1, W1, V2 and

I2 at each step.4) Repeat the procedure till about 125% of full load.

OBSERVATION TABLE:

Sr.No.

Primary Voltage

V1 (Volt.)

Primary Current

I1 (Amp.)Power InputW1 (Watts)

Secondary Voltage

V2 (Volt.)

Secondary Current

I2 (Amp.)

1

2

3

4

5

6

CALCULATIONS:

1) Full load Secondary current ( I2) =

kVA ratingV 2 ( rated )

2) Power Output (W2) = V2 × I2 Watt

3) % Efficiency =

Power output (w2)Power input (w1) ¿100


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3) % Regulation =

V2 ( 0 )−V 2

V2 (0 ) ¿100


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RESULT TABLE:

Obs. No. Power output (W2) % Efficiency % Regulation1

2

3

4

5

6


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Graphs: Plot the graphs of % Efficiency and % Regulation Verses Output Power

Conclusion:

As the load on the transformer increases the efficiency of the transformer goes on increasing

until about full load and starts decreasing thereafter. The voltage regulation goes on

increasing almost linearly with increase in load.

ASSIGNMENT ON EXPERIMENTS

EXPERIMENT NO. 1

1. State different types of wires.

2. What are the different types of switches and where they are used?

3. What are the different types of fuses and how they are rated?

4. What are the different types of sockets?

5. What are the different types of plugs?

6. What are the different types of lamp holders and where they are used?

7. What are the different types of cables?

8. Explain different parts of cable.

EXPERIMENT NO. 2

1. State general safety precautions taken while working with electricity?

2. Explain necessity of earthing?

3. State different the types of earthing?

4. What is energy conservation?

5. What are different techniques to achieve energy conservation?

6. What is energy audit?

7. Why energy audit is important?

EXPERIMENT NO. 3

1. What are the different types of lamps?

2. What are the different types of fluorescent lamp?

3. What is use of electromagnetic ballast in fluorescent lamp?

4. What is use of capacitor in fluorescent tube?

5. Enlist different parts of fluorescent tube and CFL.

6. State applications of fluorescent lamp


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7. State applications of compact fluorescent lamp

8. State applications of mercury vapour lamp

9. State applications of sodium vapour lamp


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EXPERIMENT NO. 4

1. What is effect of temperature on resistance of conductor?

2. What is effect of temperature on resistance of insulator?

3. What is the resistance temperature coefficient (α)?

4. State/explain effect of temperature on α?

EXPERIMENT NO. 5

1. Classification / types of DC networks

2. State Thevenin’s theorem?

3. Application of Thevenin’s theorem?

4. State superposition theorem?

5. Procedure of conversion any network /circuit to Thevenin’s circuit?

6. State Maximum power transfer theorem?

7. State formula for maximum power transferred to the load?

8. Use Kirchoffs laws to find current in 4Ω resistance as shown in fig. Hence verify

your result by Thevenin’s and Superposition Theorem Theorem. All the resistances

are in ohm

EXPERIMENT NO. 6

1. What do you mean by Resistor (rheostat), Inductor and Capacitor? Explain their

functions

2. Define inductive reactance?

3. Define capacitive reactance?

4. What is impedance?

5. What is power factor?

6. State formulas for Z, XL, XC, cosΦ?


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7. Comments on power factor for individual devices (Pure R, L, and C)?

8. Comments on power factor for RL series circuit

9. Comments on power factor for RC series circuit

10. Comments on power factor for RLC series circuit

11. Comments on power factor for RLC parallel circuit

EXPERIMENT NO. 7

1. Explain what is star connection?

2. Explain what is Delta connection?

3. Explain the concept of phase values

4. Explain the concept of line values

5. State relation between line and phase values of voltage and current in star

6. State relation between line and phase values of voltage and current in delta

EXPERIMENT NO. 8

1. State Faraday’s Laws of Electromagnetic Induction?

2. State Lenz’s Law?

3. Explain the concept mutually induced E.M.F and where this concept is used?

4. Explain the concept of self induced E.M.F and where this concept is used?

5. Explain the concept dynamically induced E.M.F and where this concept is used?

6. State equations for statically & dynamically induced E.M.F?

7. What is transformer, why it is required and where it is used

8. Explain various parts of transformer

9. Explain what primary and secondary winding is. Why they are named so?

10. Explain working principle of transformer

11. Explain different types of ratios in transformer

12. What do you mean by dimmerstat and why it is named so.

13. State various losses in transformer.

14. What do you mean by regulation and efficiency of transformer? Write formulae for

the same.


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