BEE Lab Manual
BASIC ELECTRICAL ENGINEERING
(FIRST YEAR ENGINEERING)
LAB MANUAL
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S COLLEGE OF ENGINEERING
BARAMATI.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 1
BEE Lab Manual
------------------------------------------------------------------------------------------------------------1.
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) Cross Linked Poly Ethylene wires (XLPE)
5) Fibre Insulated wires
5) Flexible wires
6) 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) Wires
In 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
rubber insulated conductors. P.V.C. being a thermoplastic softens at high temperatures.
Therefore, it should not be used where; extreme temperatures are likely to occur. For
example, it should not be used for making connections to heating appliances.
X. L. P. E. (Cross Linked Poly Ethylene) Wires
Now a days XLPE insulated cables are widely used for industrial applications. It has certain
advantages over PVC insulated wires. Its heat resistant properties are good as compared to
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
PVC and hence these are used for underground applications, carrying heavy currents and
bigger size cables.
Fibre Insulated Wires
Theses are used for connections in heaters, geysers etc. where environment temperature is
very high. Fibre has very good heat resistant as well as insulating properties. Fibre sleeves are
also used in some cases.
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) Flexible cables
b) Armoured 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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
General Construction of the Cable
Conductor
Insulation
Lead Sheath
Bedding
Armouring
Serving
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
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
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
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., C.T.S., P.V.C. and X.L.P.E. wires. Now a days, PVC & XLPE insulated
wires and cables are popularly 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. Standard sizes of wires are 1/18, 3/20, 3/22, 7/20, 7/22,
36/48, 42/48 etc where figure in numerator are number of strands and those in denominator
are sizes of individual strands in standard wire gauges (SWG). Metric sizes of wires are 1.5,
2.5, 4, 6, 10, 16, 25, 35, 50, 75, 120, 150 sq.mm etc in which wires upto 10 sq.mm are
available in single strand and further sizes are in multi strand. Normally 2, 3, 4 core cables
are available but cables of 3.5 cores are also available in higher ratings where ½ core mean
size of fourth core is ½ the size of other cores. Cables in further number of cores are used for
telephonic and control systems.
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.
Push Buttons are used in automation & electric control circuits.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
TYPES OF SWITCHES
SPST
Two way
Two way center off
H.R.C. CARTRIDGE FUSE
E
Intermediate
M
DPST
C
DPDT
B
P
E - FUSE ELEMENT
C - CARTRIDGE
T.P.S.T. Switch
PUSH BUTTON
P - QUARTZ POWDER
B - CONTACT BLADES
M - METAL END CAPS
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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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.
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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HRC Fuse Cartridge
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
Part B: Control of lamps connected in parallel (looping system):
Equipment required:
Single Pole switches: 2 Nos.
Connecting wires
Bulbs (40 Watt) :
2 Nos.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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LOOPING IN SYSTEM
Ph
S1
S2
S3
1 PH, 230 V, 50Hz
A.C. SUPPLY
L1
L2
L3
N
TWO POLE
6A MCB
S1 , S2 & S3
SINGLE POLE SWITCHES
STAIRCASE WIRING
LAMP (L1)
Ph
1 PH, 230 V, 50Hz
A.C. SUPPLY
N
a
a
b
(S1)
b
TWO POLE
6A MCB
S1 S2
(S2)
TWO WAY SWITCHS
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.
Part C: Staircase wiring:
Equipments required:
Two-way switches:
Bulbs (40 Watt):
Connecting wires
2 Nos.
1 No.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
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 of wiring installations & machines.
Objectives: To get familiar with the use of megger
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.
Insulation Resistance Test: 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 of the conductors. Insulation resistance can be measured with the help of 500 V or
1000 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 of equipment or
winding and earth terminal to any point on the earth continuity of the system.
Rotate the handle of megger with hand of approx 300 rpm and note down insulation
resistance. This resistance must not be less than 1 M-Ohm.
Observation Table:
Sr. No.
Insulation resistance between
conductor or winding and earth
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Insulation resistance between
conductors or windings
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-----------------------------------------------------------------------------------------------------------2. 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.
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).
FLUOROSCENT TUBE WITH
A GLOW TYPE STARTING SWITCH
FLUOROSCENT TUBE WITH
THERMAL TYPE STARTING SWITCH
S
S
R
C2
E1
G
C2
E2
E1
L
E1,E2 : Main Electrodes
C1,C2 : Capacitor
L : Choke
G : Glass Tube
S : Switch
G
E2
L
C1
E1 E
, 2 : Main Electrodes
C1
C1 C
, 2 : Capacitor
L : Choke
1PH, 230V
50Hz, A.C.
Supply
G : Glass Tube
R : Heater Element
1PH, 230V
50Hz, A.C.
Supply
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
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
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.
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
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 1/5th 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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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COMPACT FLUORESCENT LAMP
COLOUR:
1) When single phosphors coating is used inside the lamp it produce a cool white light.
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
PART C:
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.
MERCURY VAPOUR LAMP
L
1PH, 230 V, 50 Hz,
A.C. Supply
C
G2
A
G1: Inner Glass Tube
E1
G 2: Outer Glass Tube
E1 , E2: Main Electrodes
R
R : High Resistance
L : Stabilizing Choke
E2
G1
C : Capacitor
A : Auxiliary Electrode
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
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.
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.
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
SODIUM VAPOUR LAMP
L
E2
E1
T
C
1PH, 230V, 50 Hz
A.C. Supply
G2
G1
E 1, E2: Electrodes
L : Stabilizing choke
C : Capacitor
T : Transformer
G 1 : Outer Glass Tube
G 2 : Inner Glass Tube
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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-----------------------------------------------------------------------------------------------------------3.
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. Megger tests
should be carried out for checking insulation resistance with respect to earth, between
two conductors etc. with the help of a Megger.
2. Earth resistance shall be checked with the help of Earth Tester. Other tests such as
continuity test, polarity test for single pole switches shall be performed using a
Multimeter or Continuity Tester 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 Tools like screwdrivers, pliers, line testers etc. shall be used.
10. The plug should never be removed by pulling the wires connected to it.
11. 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.
Usually earthing is connected at two different points to any equipment as shown in the figure.
Earth pits are also looped together to have a sound earth connection. Maximum permissible
limit of earth resistance is 5 ohms.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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Earthing has following important uses:
1) To divert fault current and leakage current accumulated on the metallic body of the
equipment, to the earth safely. Thus saving 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 current.
2) To maintain the line voltage constant.
3) To protect tall buildings and structures from atmospheric lightening.
4) To protect all the machines, fed from overhead lines, from atmospheric lightening.
5) 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.
6) To serve as a zero potential terminal in control and electronic circuits.
.
Earthing:
Conventional method of earthing is as shown in the figure. A pit of about 10 ft is made
depending on the quality of the earth. Earth plate of conductive material like copper is placed
at the bottom connected with a flat strip of same material. A pipe is placed for pouring water.
This pit is filled with layers of charcoal, common salt, again charcoal and finally it is
completed by soil. A small chamber is constructed at ground level taking earth flat & pouring
pipe together.
EARTH PIT
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
EARTH CONNECTIONS
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BEE Lab Manual
A recently developed Safe Earth Electrode (SEE) is used as an alternative to the conventional
earthing method. It is safe, easy to install and time & labour saving method. A ready prepared
earth electrode of about 4” or 6” diameter having earth connection at one end is available in
the market. A hole of suitable size is drilled in the ground and SEE is inserted in it. Earth
wire is connected and water is poured around it. A small earth pit is also constructed at the
ground level. Thus earthing becomes ready.
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
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 
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual


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.
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
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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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.
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
-----------------------------------------------------------------------------------------------------------4. 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.
2.
3.
4.
Testing Vessel
Water Heating Coil
RTD Probe (PT 100)
Multimeter
--- 1 No
--- 1 No
--- 1 No
--- 1 No
Theory:
If a metallic conductor having resistance of Ro at 0c is heated to tc and increase in
resistance be Rt, then the increase in resistance depends…..
o directly on its initial resistance
o directly on the rise in temperature and
o on the nature of material of the conductor.
 If change in resistance
R = Rt – Ro
then
Rt – Ro  Ro . ( t – 0 ) or
Rt – Ro =  Ro . t …….. (i)
Where  (alpha) is a constant and is known as Temperature Co-efficient of Resistance of the
conductor. Re-arranging eq. (1), we get
Rt - Ro
 =  ……….. (ii)
Ro . t
Hence the temperature co-efficient of a material may be defined as the increase in resistance
per ohm original resistance per c rise in temperature.
From eq. (i), we find that Rt = Ro ( 1 +  . t ) ………. (iii)
This equation is true for both rise as well as fall in temperature. For decrease in temperature
of conductor, resistance also decreases.
The value of temperature co-efficient  is not constant but depends on the initial temperature
at which heating is initiated i. e. on which the increment in resistance is based. When the
increment is based on the resistance measured at 0c, then  has the value of o.

Rt - Ro
o = 
Ro . t
……….. (similar to eq. ii)
So for heating of the conductor of resistance Ro at 0c to tc,
The Resistance Rt = Ro (1 + o . t ) ….….. (similar to eq. iii)
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
Similarly if it is cooled from tc to 0c,
The Resistance Ro = Rt  1 + t ( - t )  = Rt (1 - t . t ) …….. (iv)
And
Rt - Ro

t = 
……….. (v)
Rt . t
Where t is the temperature co-efficient of resistance of the conductor at tc.
Conductor:
Silver is the best conductor but its cost limits its use to special circuits only. Copper and
Alluminium are most commonly used conductors. Copper has higher conductivity than
alluminium but is more expensive & heavier than alluminium. Alluminium has about 60% of
the conductivity of copper, but its lightness makes long spans possible.
RTD PT-100:
Remote Temperature Detector (RTD) type PT-100 is platinum resistance thermometer, which
offers excellent accuracy over a wide range i. e. from -200c to 850c. The principle of
operation is to measure the resistance of a platinum element which exhibits almost a linear
relationship with temperature over a small temperature range. PT-100 has a resistance of 100
ohms at 0c and 138.4 ohms at 100c, i. e. a 1c change in temperature will cause 0.384 ohm
change in resistance.
Diagram:
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
Procedure:
1. Place water in the vessel such that the specimen coil and PT-100 are
sufficiently immersed in the water.
2. Measure resistance of the specimen coil using multimeter.
3. Switch ON the panel supply and note down the initial temperature.
4. Start heating by switching ON the supply to heating coil through temperature
relay. Increase in temperature will start.
5. Note down the resistance of the specimen coil at every 1c rise in temperature.
6. Take 7 to 8 readings and switch OFF the heating coil supply.
7. Switch OFF temperature relay supply and panel supply.
8. Calculate temperature co-efficient of coil at all recorded temperatures. Also
calculate Resistance and Temperature co-efficient of resistance at 0c.
9. Plot the graph of Resistance verses Temperature. Extrapolate it to cut Y axis
and find out Ro.
Safety Precautions:
1. Do not touch to the hot apparatus.
2. Do not allow heating above 40 - 45c.
Observation Table:
Sr.No.
Temp.
Tc
Resistance
R
Calculated Values
t
o
Ro
1
2
3
4
5
6
7
Average Values
Values by Graph
Conclusion:
As temperature of coil increases, its resistance goes on increasing. Hence the specimen coil
has a positive temperature coefficient of resistance.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 24
BEE Lab Manual
-----------------------------------------------------------------------------------------------------------5. Verification of Kirchhoff’s Laws and Superposition Thereom
-----------------------------------------------------------------------------------------------------------Aim: To verify a) Kirchhoff’s Laws and
b) Superposition Theorem
PART A : To Verify Kirchhoff’s Laws
Apparatus: 1.
2.
3.
4.
5.
Experimental kit.
Dual power supply (0-30 V D.C., 2 A)
D.C. milliammeter (0-500mA)
Multimeter
Connecting wires
Kirchhoff’s Current Law (KCL):
The algebraic sum of currents meeting at a junction or node in an electric circuit is zero.
Consider five conductors carrying currents I1, I2, I3, I4, and I5 meeting at a point O as shown in
the figure. Assuming the incoming currents to be positive and outgoing currents negative, we
have
I1 + (- I2) + I3 + (- I4) + I5 = 0
I1 - I2 + I3 - I4 + I5 = 0
I1 + I3 + I5 = I2 + I4
Thus above law can also be stated as the sum of currents flowing towards any point in an
electric circuit is equal to the sum of currents leaving from the point.
Procedure:
1. Construct the circuit as per diagram using the values R1, R2 and R3.
2. Adjust the source voltage between 0 to 30 Volts and note down the currents I1,
I2 and I3.
3. Calculate I1, I2, I3 and compare calculated values with the observed values.
Both calculated and observed values should be nearly equal.
4. Calculate sum of observed values and this should be near to zero.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 25
BEE Lab Manual
Observation Table:
Calculated Values
V
I1
I2
Sum of
Observed Values
Observed Values
I3
I1
I2
I3
I1 + I2 + I3 ≈ 0
15
20
25
Conclusion:
Since calculated and observed values are matching and also sum of observed currents is
almost zero, hence Kirchhoff’s Current Law is verified.
Kirchhoff’s Current Law (KCL):
The algebraic sum of all the voltage in any closed electric circuit or mesh or loop is zero.
If we start from any point in a closed circuit and go back to that point, after going round the
circuit, there is no increase or decrease in potential at that point. This means the sum of emfs
and sum of voltage drops or rises meeting on the way is zero.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
Procedure:
1. Construct the circuit as per diagram using the values R1 and R2.
2. Adjust the source voltage between 0 to 30 Volts and note down the current I
and voltage across R1 and R2 i. e V1 and V2 respectively.
3. Calculate V1 and V2 and compare calculated values with the observed values.
Both calculated and observed values of voltages should be nearly equal.
4. Calculate sum of observed voltages plus source voltage and this should be
near to zero.
Observation Table:
Supply
V
Current
I
Calculated Voltages
V1=I*R1
V2=I*R2
Observed Voltages
V1
Sum of Observed Plus
Supply Voltages
V2
V1 + V2 + V ≈ 0
15
20
25
Conclusion:
Since calculated and observed values are matching and also sum of observed plus supply
voltages is almost zero, hence Kirchhoff’s Voltage Law is verified.
Apparatus: 1.
2.
3.
4.
5.
PART B : To Verify Superposition Theorem
Experimental kit.
Dual power supply (0-30 V D.C., 2 A)
D.C. milliammeter (0-500mA)
Multimeter
Connecting wires
Theory:
In a linear network containing more than one independent source, the resultant current in any
element is the algebraic sum of the currents that would be produced by each independent
source acting alone, all the other independent sources being represented meanwhile by their
respective internal resistances.
The independent voltage sources are represented by their internal resistances if given or
simply with zero resistances i. e. short circuits if internal resistances are not mentioned. The
independent current sources are represented by infinite resistances i. e. open circuits.
A linear network is one whose parameters are constant i. e. they do not change with voltage
and current.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 27
BEE Lab Manual
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 28
BEE Lab Manual
Procedure:
1. Construct the circuit as per the circuit diagram in fig. (iv) using the values R1,
R2 and R3 and sources V1 and V2.
2. Adjust the source voltages between 0 to 30 Volts and note down the current I3
through R3. Select 2 to 3 different sets of source voltages and record the
current I3 at respective sets of source voltages.
3. Replace voltage source V2 by its internal resistance i. e. short circuit as shown
in the circuit diagram in fig. (v). Record the currents I’3 by setting same
voltages as per sr. no. 2 above.
4. Replace voltage source V1 by its internal resistance i. e. short circuit as shown
in the circuit diagram in fig. (vi). Record the currents I”3 by setting same
voltages as per sr. no. 2 above.
5. Calculate currents I’3 and I”3 and add together to get the current I3. Compare
calculated values with the observed values of current I3. Both calculated and
observed values of currents should be nearly equal.
6. Calculate sum of observed values of currents I’3 and I”3 and this should be
near to observed current I3.
Observation Table:
Obs.
No.
1
2
3
V1
V2
I’3
Calculated Values
I”3
I3 = I’3 + I”3
I’3
Observed Values
I”3
I3 = I’3 + I”3
Conclusion:
Since calculated and observed values are almost matching and sum of independent sources
acting alone also almost equals the current produced with both sources connected in the
circuit, hence Superposition Theorem is verified. The differences may be due to :
i) Assuming the voltage sources to be ideal
ii) Instrumental errors
iii) Manual errors
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 29
BEE Lab Manual
-----------------------------------------------------------------------------------------------------------6. SINGLE PHASE TRANSFORMER
-----------------------------------------------------------------------------------------------------------PART A) VOLTAGE RATIO & CURRENT RATIO:
AIM: To determine voltage ratio & current ratio of a single phase transformer.
APPARATUS:
1) Single phase transformer (230/115V)
2) Dimmerstat (230/0-270V,15 A)
3) A.C. Voltmeters (0-150-300V)
4) A.C Ammeters (0-5A)
-----
1 No.
1 No.
2 Nos.
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;
N1
is called as the ‘turns ratio’.
N2
For ideal transformer the power equation is;
V1 I1 = V2 I2
Where,
………….Eqn I
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,
V2 I1 N 2


k
V1 I 2 N1
The ratio ‘k’ is called as the ‘transformation ratio’.
V
The ratio 1 is called as the ‘voltage ratio’
V2
I
The ratio 1 is called as the ‘current ratio’
I2
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 30
BEE Lab Manual
CIRCUIT DIAGRAM : VOLTAGE AND CURRENT RATIO OF TRANSFORMER
CURRENT RATIO TEST
(0-5A)
(0-5A)
A
A
PH
1PH, 230V, 50 Hz A.C.
SUPPLY
N
1-PH, 240 / 0 - 270 V, 15 A
AUTOTRANSFORMER
1PH, 230V / 230V, 1kVA
TRANSFORMER
VOLTAGE RATIO TEST
PH
1PH, 230V, 50 Hz A.C.
SUPPLY
(0-300V)
V
V
(0-300V)
N
1-PH, 240 / 0 - 270 V, 15 A
AUTOTRANSFORMER
1PH, 230V / 230V, 1kVA
TRANSFORMER
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.
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 31
BEE Lab Manual
OBSERVATION TABLE:
Obs.
No.
Current Ratio Test
Voltage
V1
V2
Ratio
(Volt)
(Volt)
V1/V2
Current Ratio Test
Current
I1 (Amp) I2 (Amp)
Ratio
I1/I2
1
2
3
RESULTS:
1) The transformation ratio is________.
2) The voltage ratio is
_________.
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
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 32
BEE Lab Manual
PART B) EFFICIENCY AND REGULATION BY DIRECT LOADING METHOD.
Aim: To determine efficiency and regulation by direct loading.
Apparatus:
1. Single PhaseTransformer
2. A. C.Voltmeter
3. A. C.Ammeter
4. Dimmer stat
5. Single Phase Lamp bank (Resistive load)
6. Wattmeter
-------------
1 kVA, 230/230 V
(0-300V)
(0-5A)
230V/0-270V, 15A
(230V, 10Amp.)
(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)
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 V1, I1, W1, V2 and
I2 at each step.
4) Repeat the procedure till about 125% of full load.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 33
PH
1-PH, 230 V
50 HZ, A.C.
SUPPLY
N
1 PH., 240 / 0 - 270 V,15 A
AUTOTRANSFORMER
A
(0-5A)
C
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
(0-300V) V
A
(0-5A)
1 PH, 230 / 230 V, 1 kVA
TRANSFORMER
V
(0-300V)
V
5A,300V
M
L
CIRCUIT DIAGRAM - DIRECT LOAD TEST ON SINGLE PHASE TRANSFORMER
1-PH, LOAD
LAMP BANK
(230 V, 10 A)
BEE Lab Manual
Page 34
BEE Lab Manual
OBSERVATION TABLE:
Obs.
No.
Primary
Voltage
V1
(Volt.)
Primary
Current
I1
(Amp.)
Power
Input
W1
(Watts)
Secondary Secondary
Voltage
Current
V2
I2
(Volt.)
(Amp.)
1
00
Power
Output
W2
(Watts)
Efficiency
%
Regulation
%
---
---
---
2
3
4
5
6
CALCULATIONS:
1) Full load Secondary current ( I2) =
kVA rating
V2 rated 
2) Power Output (W2) = V2 × I2 Watt
3) % Efficiency =
3) % Regulation =
Power output w 2 
 100
Power input w 1 
V20   V2
V20 
 100
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 35
BEE Lab Manual
-----------------------------------------------------------------------------------------------------------7. THEVENIN’S THEOREM
-----------------------------------------------------------------------------------------------------------Aim: To verify Thevenin’s theorem
Apparatus: 1. Experimental kit.
7. Dual power supply (0-30 V D.C., 2 A)
8. D.C. milliammeter (0-500mA)
9. Multimeter
10. Connecting wires
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.
RTH
a
A resistive circuit
a
Ports
VTH
b
b
(Thevenin's equivalent circuit)
‘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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 36
BEE Lab Manual
RTH
I
a
RL
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;
VTH
I=
b
VTH
RTH  R L
Circuit Diagram:
CIRCUIT DIAGRAM - THEVENIN'S THEOREM
R1
R2
+
A (0-500 mA)
_
V1
(0-30 V)
V2
(0-30 V)
RL
R3
R4
Procedure:
1. Apply certain voltages from the two voltage sources V1 and V2. Observe and note
down the current ‘IL’ in the load resistor ‘RL’ 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’.
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.
6. Calculate I’L using the formula and compare it with IL .
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 37
BEE Lab Manual
Observation Table:
Obs.
No.
V1
V2
IL
VTH
RTH
RL
Current in load resistor by Thevenin’s Theorem (I’L)=
VTH
RTH  R L
I’L ( ≈ IL )
1
2
3
Calculation:
Conclusion:
It is seen that the actual value of load current IL & the value of load current calculated using
Thevenin’s theorem I’L are approximately same, hence Thevenin’s Theorem is verified.
The differences may be due to:
i)
Assuming the voltage sources to be ideal
ii)
Instrumental errors
iii)
Manual errors
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 38
BEE Lab Manual
8. R-L-C SERIES CIRCUIT
-----------------------------------------------------------------------------------------------------------AIM : To study R-L-C series circuit.
APPARATUS:
1) R-L-C series circuit
2) A.C. Ammeter
3) Digital Multimeter / AC Voltmeter (0-300V)
----
1 No
1 No
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
V
Also, I 
Z
‘ Z ’ is known as impedance of the circuit. It is given as; Z  R  j ( X  X ) .
L
The magnitude of impedance is given as; Z =
R2  (X
L
X
C
C
)2
Where,
XL = Inductive reactance = 2L Ohm ( ‘L’ is in Henry)
XC = Capacitive reactance =
1
Ohm (‘C’ is in Farad)
2fC
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.) =
R
= cos 
Z
PROCEDURE:
1)
2)
3)
Connect the circuit as shown in the diagram.
With the help of dimmerstat, vary the voltage V in circuit.
For each voltage setting, read and note down the current I and voltages VR, VL, VC &
VR-L with the help of multimeter.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 39
BEE Lab Manual
CIRCUIT DIAGRAM OF R-L-C SERIES CIRCUIT
Ph
1PH, 230V,
50 Hz
A.C.Supply
R
L
VR
VL
C
VC
VRL
A
(0 - 1 A)
VT
N
V
(0 - 300V)
OBSERVATION TABLE:
Obs.
No.
V
Volts
I
Amps
VR
Volts
VL
Volts
VR-L
Volts
VC
Volts
1
2
CALCULATIONS:
VR

I
V sin  L
ii) XL = L

I
V sin C
iii) XC = C

I
X
iv) L = L Henry
2f
A) PARAMETERS : i) R =
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 40
BEE Lab Manual
v) C =
B) POWERS:
1
Farad
2fX C
i) PR = VR  I = I2  R = _________________Watt
ii) PL = VL  I  cos L = __________________Watt
iii) PC = VC  I  cos c = __________________Watt
iv) P = V  I  cos  = __________________Watt
Verify that, PR + PL +PC = PT ( ≈ P )
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  = ____________.
Procedure for plotting Phasor Diagram:
1)
2)
3)
4)
5)
6)
7)
8)
9)
Draw phasor diagrams for all the readings
Current I should be taken as reference phasor,
Choose a suitable scale for voltage.
VR (OA) should be drawn in phase with current.
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.
Measure L made by vector AB with vector I.
With ‘O’ as center & radius equal to V, an arc is drawn. Similarly with ‘B’ as center
& radius equal to Vc, an arc is drawn to cut the above arc at C. Join AC & OC.
Measure C made by vector AC with vector I.
Measure  made by vector OC with vector I.
RESULT TABLE:
Obs.
No.
R
L
(Ω) (H)
C
(F)
P
P
P
P
P + P +P
R
L
C
R
L
C
cos cosL cosC Watt Watt
Watt Watt = PT Watt
1
2
CONCLUSION:
Sum of power consumed by individual components i. e. Resistance ‘R’, Inductor ‘L’ and
Capacitor ‘C’ almost equals the power consumed by entire circuit.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 41
BEE Lab Manual
9. 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
2) A.C.Voltmeter
3) A.C. Ammeter
-------
(3 x 100 W)
(0 – 300 V)
(0 – 2 A)
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:
VRY  V RN  V NY
VYB  VYN  V NB
VBR  V BN  V NR
 V RN - VYN
 VYN - V BN
 V BN - V RN
From phasor diagram,
VRY  2  VRN  cos 30  3 VRN
i.e., VL  3 VPH
Also IR, IY, IB are the three line currents, as well as the three phase currents
i.e., IL=IPH
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 42
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
N
B
Y
4P, 415V, 10A
MCB
R
3 PH, 415 V, 50Hz
AC SUPPLY
A3
A2
A1
C
E3
E2
E1
V
3 PH, 440 V / 0 - 470 V, 15 A
AUTOTRANSFORMER
N
B
Y
R
(0-600V)
A
B1
Y1
V
(0 - 300V)
R1
B2
Y2
R2
3PH, 415V, 10 A,
LAMP BANK (STAR CONNECTED)
(0 - 5A)
CIRCUIT DIAGRAM OF STAR CONNECTION
BEE Lab Manual
Page 43
B
Y
E3
E2
A2
A3
E1
A1
V
THREE POLE MCB
(15 A)
3 PH, 440 V / 0 - 470 V, 15 A
AUTOTRANSFORMER
R
3 PH, 440 V, 50 Hz,
A.C. SUPPLY
(0-600V)
A
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
B1
Y1
R1
B2
(0 - 5 A)
Y2
A
R2
3 PH, 440 V, 10 A
LAMP BANK (DELTA CONNECTED)
(0 - 10 A)
CIRCUIT DIAGRAM FOR DELTA CONNECTION
BEE Lab Manual
DELTA CONNECTION:
Page 44
BEE Lab Manual
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,
I R  I RY - I BR
I Y  I YB - I RY
I B  I BR - I YB
From phasor diagram,
I R  2  I RY  cos 30  3 I RY
i.e., I L 
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:
Line
Voltage
VL (Volt)
Connection
Phase
Voltage
VP (Volt)
Voltage
Ratio
VL/ VP
Line
Current
IL (Amp)
Phase
Current
IP (Amp)
Current
Ratio
IL/ IP
Values by
Graph
VL/ VP =
1
Star
2
IL/ IP =
1
Delta
2
PHASOR DIAGRAM: Draw phasor diagram to the scale for one case each for star and delta
CONCLUSION:
ASSIGNMENT ON EXPERIMENTS
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 45
BEE Lab Manual
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. 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
7. State applications of compact fluorescent lamp
8. State applications of mercury vapour lamp
9. State applications of sodium vapour lamp
EXPERIMENT NO. 3
1.
State general safety precautions taken while working with electricity?
2.
3.
Explain necessity of earthing?
State different the types of earthing?
4.
5.
What is energy conservation?
What are different techniques to achieve energy conservation?
6.
7.
What is energy audit?
Why energy audit is important?
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 46
BEE Lab Manual
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?
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
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BEE Lab Manual
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.
DEPARTMENT OF ELECTRICAL ENGINEERING
VIDYA PRATISHTHAN’S CLLEGE OF ENGINEERING, BARAMATI
Page 48