Lab Manual - 1st Semester & 2nd Semester

JEE-Lab(EE-1202)/PBC/05

DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR

BASIC EE LABORATORY First/ Second Semester Expt.No.1202-/1(a)

FAMILIARISATION EXPERIMENT

(VARIAC, POTENTIAL DIVIDER, MCV, MIV, MCA, MIA)

Object : 1. To become familiar with ‘POTENTIAL DIVIDER’ and ‘VARIAC’

2. To become familiar with Moving-coil and Moving-iron type ammeter and voltmeters and to understand the limitations of moving coil type instruments.

THEORY: 1. POTENTIAL DIVIDER It is a device by which we can obtained a variable output d.c. voltage (whose magnitude can be varied from zero to the supply voltage) from a fixed d.c. supply.

Fig. 1(a) Fig. 1(b)

With reference to Fig. 1(a), if R = Resistance between moving contact points JJ R1 + R2 = resistance between the input terminals of the potential divider,

when no current is flowing through the output circuit

21

11 RR

VI+

=

21

2121o RR

RVR.IV+

===

1


Procedure: i) Connect MCA and MIA in series and MCV and MIV in parallel as shown in

Fig.1(b) ii) Note the positions of the moving contacts at which the output voltage is (a)

approximately zero, (b) maximum and nearly equal to the supply voltage. iii) Keep the load resistance fixed. Vary the output voltage in 3 steps and record

ammeter and voltmeter readings in Table I and of the data sheet. iv) Record what happens when terminal connections of MCA and MIA and also

MCV and MIV are reversed, in Table II of the Data Sheet. THEORY : II – VARIAC Description: It is an a.c. device used to obtain variable output alternating voltages

(magnitude can be varied from zero to a voltage even higher than the supply voltages).

Procedure:

1. (i) Make connection as shown in Fig.2(a) below:

Fig. 2(a) Fig. 2(b)

(ii) Vary the position of the moving contact and record ammeter and voltmeter readings in Table III of the Data Sheet.

REPORT: 1(a) Moving coil instruments can measure only................................ 1(b) Moving iron instruments can measure .....................................

2. A moving-coil ammeter is giving deflections in the wrong direction. How can you make it to read in the proper direction?

3. You are given a moving coil and a moving iron instrument. Can you

recogrnise the meters from their scales? 4. Can you use a potential divider for obtaining variable d.c. supply from a

fixed a.c. supply?

2


3

5. What are the differences between a variac and a potential divider? DATA SHEET

TITLE OF THE EXPERIMENT:.................................................................................. PERFORMED BY:....................................................................... Date :........................................... Roll No............................. Experiment No................... Apparatus used:

No. Item Range Lab. No. A) EXPERIMENTAL DATA:

TABLE – I

Readings of No. of Obvs. MCA MIA MCV MIV

Remarks

TABLE – II METER Normal Connection Reversed Connections MCA MIA MCV MIV


4

DEPARTMENT OF ELECTRICAL ENGINEERING

BENGAL ENGINEERING & SCIENCE UNIVERSITY, SHIBPUR BASIC EE LABORATORY First/ Second Semester Expt.No. 1202-/1(b)

TITLE OF THE EXPERIMENT: “FAMILIARIZATION WITH THE WATTMETER” Object : To become familiar with wattmeter connections at different current and

voltage ratings. Theory : A wattmeter is an instrument which measures electrical power. Power = voltage X current. Thus a wattmeter has a voltage or pressure coil which senses voltage across the circuit of which the power is to be measured and a current coil which senses the current in the circuit. Thus a wattmeter will read when its current and pressure coils are excited simultaneously. So a wattmeter must have at least four terminals. The symbolic representation is shown in FIGURE-1. However in portable wattmeter, quite often many more terminals are provided for measuring power at different current and voltage ranges. Procedure : (i) Make connections as shown in the FIGURE-1 with current range of 2.5A and voltage range of 125V/150V. (ii) Adjust the variac output voltage to 125V/150V allowing a current to flow through the load. Record the wattmeter reading in TABLE-1 of the data sheet. (iii) Change the voltage range to 250V/300V and record the wattmeter reading in table-2 (iv) Change the current range to 5A and record the wattmeter reading in

TABLE-1. (v) Change the voltage range to 125V/150V and record the wattmeter

reading in TABLE-1. (vi) See what happens when,

a) the current coil is reversed b) The pressure coil is reversed c) Both current and pressure coils are reversed and complete

TABLE-1.


Report : 1) Calculate multiplying factors from the current and voltage ranges used. When power factor is unity, Voltage range used X Current range used X Power factor (Cosø) Multiplying Factor = --------------------------------------------------------------------------------------- Full scale division 2) A wattmeter is giving negative deflection. How can you give the deflection in the correct direction? 3) How do you specify a wattmeter?

5

PRE

CURRENT COIL

VARIAC

1-PH., 230V, 50 Hz A.C.SUPPLY

DOUBLE POLE REWIRABLESWITCH FUSE UNIT

CIRCUIT DIAGRAM FOR FAMILIARIZATION OF WATTMETER

MIA L

WATTME

FIG

A

SSURECOIL

COM

TER

URE-1

A

LOAD

V


DATA SHEET

“FAMILIARIZATION OF WATTMETER”

NAME: ______________________ ROLL NO.__________ DATE :__________ Apparatus used:

Sl. No. Item Range Lab. No.

1 Ammeter MIA

2 Wattmeter ___________V, __________A, p.f=_____, Mf ______ W

3 Variac 1-Phase, ________V, ________A, 50Hz VAR Experiment Data:

TABLE-1 No.of obvs. Current range Voltage range Wattmeter

reading Multiplying factor(Mf)

Power

1

2

3

4

TABLE-2

No.of obvs. Item Deflection

(Indicate positive or negative)

1 Current coil terminal “M” connected to Pressure coil. Terminal “COM” as in fig.-1

2 Current coil reversed, pressure coil as in fig.-1

3 Current coil as in fig.-1 but pressure coil is reversed.

4 Both current and pressure coil is reversed.

Signature of the teacher

6


BASIC EE LABORATORY First/Second Semester Expt.No. -1251/2 TITLE : Experimental verification of circuit theorems(For DC circuit ) (a)Superposition theorem (b) Thevenin’s theorem. (c) Maximum power transfer theorem Object : (i) To verify the theorems experimentally. (ii) To find out the current through the load resistance RL(6 Ώ) using two theorems. Theorem: Superposition Theorem In any linear bilateral network, the current at any point due to the simultaneous action of a number of e.m.fs distributed through out the network, is algebraic sum of components in the network. A component current in a network is that due to one e.m.f. acting alone with other e.m.f. replaced by their internal resistance. Thevenin’s Theorem Any two terminal active linear bilateral network can be replaced at any pair of terminals a-b by an equivalent circuit having a voltage source Eth in series with a resistance Rth where Eth is the voltage across the terminals a-b when they are open circuited and Rth is equivalent resistance between the terminals a-b looking back into network when all the voltages are replaced by their internal resistance. Maximum power theorem A resistive load connected to a dc network receives maximum power when the load resistance is equal to Thevenin equivalent resistance of the network as seen from load terminals. The current (I) in a series circuit containing load resistance RL and source resistance RS is given by

I= V/ (RL + RS) Where V is the applied voltage. So, the power P absorbed in the resistance RL is

P= [V/ (RL + RS)] 2 RL

The value of RL for which P will be maximum is obtained from the relation when RL = RS

Hence for maximum power transfer to the load, the load resistance (RL) must be equal to the source resistance (RS).

Procedure

1. Make connections as shown in the diagram.

: For Superposition Theorem:

2. Measure the current through RL when both sources (V1 &V2

3. Keeping one voltage source (V

) are present and tabulate in Table- 1.

1) in the circuit and other voltage source (V2

4. Now insert the other source (V

) replaced by their internal resistance (here assume zero) note down the ammeter reading in Table -1 with proper polarity.

2) in the circuit removing the voltage source (V1

For Thevenin’s Theorem:

) by their internal resistance (here assume zero) and measure the circuit current with proper polarity.

1. Remove the resistance RL and measure the open circuit voltage (Vth

2. Measure the resistance R

) across a&b and tabulate in table II.

th of the circuit across a&b when the two sources are replaced by their internal resistance. The resistance Rth is measured across a and b by drop method (i.e eitherV1 or V2 is connected across a and b and measure ammeter current. Then Rth = V1 or V2

3. I /ammeter current).

L =Vth /Rth + R4. Tabulate I in table –II

L

For Maximum power Transfer theorem:

1. Make connection as shown in fig (ii) 2. Switch on 30 volt dc regulated supply and so not alter RS

3. Increase R.

L ohm maximum and measure supply voltage (V), voltage across the load resistance (VRL), voltage across the source resistance (VRS

4. Keeping the supply voltage fixed, lower the load resistance (R

) and the current through the circuit and tabulate the data.

L) in another five steps and tabulates the results for different values of current.

1. (a) How will you represent ideal voltage and current sources?

Report:

(b) What is meant by linear, bilateral network? Give example. (c) Are the network theorem valid for ac circuits? (d)

2. Write the values of currents obtained by Superposition theorem, Thevenin’s theorem and experiments.

3. Draw the graph of VRS vs. I in a graph paper and determine the values of the source resistance (RS

4. Plot P vs. R).

L in a graph paper and determine the value of RL for which P is maximum. Hence compare this with RS

obtained in (2)

CIRCUIT DIAGRAM OF NETWORK THEOREM EXPERIMENT:-

10V

40! a

RL = 6!

b

A

V

50!

14V

Fig-1

Rs =

RL= V VRL

V

VRS

V 30V

Constant

Fig-2

DATA SHEET

TITLE OF THE EXPERIMENT: ……………………………………………………………………………………..

PERFORMED BY:………………………………………………………………………………………………………

Date : ………………………………… Roll No: ………………

Experiment No : ………………….

Sl. No

Apparatus Used :

Item Quantity Range /Rating Maker’s Name

Lab No.

1 Digital ammeter

2 Digital voltmeter

3

Resistance

4 DC regulated power supply

5 Main switch

Sl.No

Experimental Data:

Table-1

Particular Current/voltage 1 Current through RL with both the sources present(I) 2 Current through R for source V1 only(I1 ) Current through RL for source V2 only(I2 ) 5 Algebraic sum of I1and I 2

Table-II

Sl.No Particulars Voltage / current / resistance 1 Voltage across a and b when RL is removed(vOC ) 2 Ammeter current 3 Equivalent resistance( Req ) 4 Load current(IL )

Table-III

No. of Obvs.

Supply voltage (V) volt

Voltage across (VRS

Voltage across (V)

Volt RL

Current (I) Amp )

Volt

Value of R Power consumed in R

L

Ohm L (P)

Watt

Signature of the Teacher


10

DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING & SCIENCE UNIVERSITY, SHIBPUR

BASIC EE First / Second Semester Expt. No. 1202/3 TITLE OF THE EXPERIMENT: “STUDY OF A.C. SERIES R-L-C CIRCUIT” Object: To study an a.c. single phase circuit with reference to Power, Power Factor and Phasor Diagram. A) DETERMINATION OF PARAMETERS OF CHOKE Procedure: 1) Connect the choke as shown in figure-3. {Note: A choke is equivalent to a resistance RL and an inductance L in series, so that at any frequency ‘f’, the impedance of the choke Z=(RL

2+XL2)½, where, XL=2π

fL.} 2) Measure Power, Current and Voltage for two values of current between 0.7 and 1.1A (Adjust by means of the rheostat R1) to complete TABLE-1 of the DATA SHEET. Report : 1) Complete TABLE-1of the DATA SHEET to find RL , L and Power factor of the choke. 2) For one value of current, of TABLE-1of the DATA SHEET, calculate IRL and IXL. Choose a suitable voltage scale and draw the Phasor Diagram on a square paper to scale. Find “Cosø” and tabulate. B) DETERMINATION OF PARAMETERS OF CAPACITOR Procedure: 3) Replace the choke of Figure-3 by a capacitor and repeat the procedure (2). Complete TABLE-2 of the DATA SHEET. Report : 3) Determine capacitance C, neglecting losses in the capacitor. 4) Draw the Phasor Diagram on a square paper to scale. Find “Cosø” and tabulate.

C) R-L-C SERIES CIRCUIT : Procedure: 4) Connect as shown in figure-5 ; 5) For two values of current between 0.7 and 1.1A(adjusted by the rheostat R1), measure Power, Current and Voltage to complete TABLE. Report: 5) For one value of current from the observed data, calculate for value of RL, L and C previously determined. 6) On a square paper, draw the phasor diagram to scale following the procedure given below:-

1) Draw phasor VR and Vc (fig.-5) and find. 2) Draw phasor VL knowing -----?------ as determined before. 3) Find V=(VL+ VRf +VC) and hence the magnitude of V and “Cosø”.

4) Complete TABLE-3 of the DATA SHEET.


DATA SHEET “STUDY OF A.C. SERIES CIRCUIT” NAME: _____________________ ROLL NO.: ______________ DATE : ______________ Apparatus used:


1. Ammeter MIA

2. Voltmeter MIV

3. Wattmeter ___________V, __________A, p.f=____, Mf =______ W

Experiment Data:

TABLE-1 Observed data Calculated data No.of

obvs. V I W Z=V/I RL L p.f.=W/VI Power factor from phasor diagram

1

2

TABLE-2

Observed data Calculated data No.of obvs. V I W Z=V/I RC C P.F=

W / VI

Power factor from phasor diagram

1

2

TABLE-3

Observed data Calculated power factor No.of obvs. I VRf V W Cosø From phasor diagram

V from Phasor diagram

1

2

Signature of the teacher 13


CIRCUIT DIAGRAM

11

FIGURE-1 F

PRESSURECOIL

CURRENT COIL

CHOK

1-PH, 230V, A.C.SUPPLY 50 Hz

DOUBLE POLE REWIRABLESWITCH FUSE UNIT

CIRCUIT & PHASOR DIAGRAM FOR STUDY OF A.C. SERIES CIRCUIT

A

M

RHEOSTAT

WATTMETER

FIGURE-3

PHASOR DIAGRAM

VCOM

L M

O

VC

IVL

IGURE-2

V

E COIL

R

CIA

MIV
L


CIRCUIT DIAGRAM

12

RHEOSTAT

V=VL+VRC+VC

A

PRESSURECOIL

CURRENTCOIL

1-PH, 230V, 50 Hz A.C.SUPPLY

DOUBLE POLE REWIRABLE SWITCH FUSE UNIT

WATTMETER

M A

MI

COM

M L

V

VRf

MIV

Rf

CHOKE COIL

CAPACITOR

R L C

CIRCUIT & PHASOR DIAGRAM FOR STUDY OF A.C. SERIES CIRCUIT

PHASOR DIAGRAMFIGURE-4

FIGURE-5

I

VRf+VC

VC

VRf

V

I


14


BASIC EE LABORATORY First / Second Semester Expt.No. 1202-/4

TITLE OF THE EXPERIMENT: “SPEED CONTROL OF D.C. SHUNT MOTOR” Object : To study the two methods of speed control of a d.c. Shunt Motor.

a) Armature voltage control b) Field current control

Theory : The voltage “V” across the armature terminals of a d.c. Shunt Motor is approximately related as : V = KØn; Where,“Ø” is the flux per pole and is proportional to field

current (If). “n” is the speed of the motor. “K” is a constant of the motor.

A) By varying the armature voltage (VA), keeping the field current (If) constant, “speed variation from zero to about rated value can be obtained”.

B) By varying the field current (If),keeping armature voltage(VA) constant, “speed variation from rated to above rated value can be obtained”.

Procedure : 1) Make connection as shown in the circuit diagram.

METHOD-A 2) With minimum resistance in the field circuit (that is maximum If ),and

the potential divider in the minimum voltage position (V=0) switch on the d.c. 220V mains.

3) Apply small voltage to the armature circuit and observe that the motor runs at a steady speed. Note armature voltage, speed and field current.

4) Increase V to the maximum value in 4(four) steps and complete DATA SHEET of TABLE-1. METHOD-B

5) Keeping the potential divider in the maximum voltage position, decrease field current (If). Observe that the speed increases. Note field current (If), speed (n) and armature voltage (V).


6) Decrease field current (If) in 4(four) steps till the motor speed is about 1750 r.p.m and complete the DATA SHEET of TABLE-2. Report : 1) Draw curves showing –

a) Speed (n) versus armature voltage (VA), with field current (If) constant.

b) Speed (n) versus field current (If), with armature voltage (VA) constant.

220V, D.C.SUPPLY DOUBLE POLE REWIRABLE

SWITCH FUSE UNIT

V M

A

A1

A2

SH2SH1

POTENTIALDIVIDER

SHUNT FIELD WINDING

CIRCUIT DIAGRAM FOR SPEED CONTROL OF D.C. SHUNT MOTOR

ROTATING ARMATURE

FIGURE-1

M

MCV

15

RHEOSTATCA


DATA SHEET

“SPEED CONTROL OF D.C. SHUNT MOTOR” NAME:____________________ ROLL NO. _____________ DATE : _____________ Apparatus used:


1. Ammeter MCA 2. Voltmeter MCV 3. Tachometer

Machine under test: D.C. Shunt Motor Voltage (V): _____________ , Power: _____________ , Current: ______________ Speed: ________________ , Lab. No. ____________ Experiment Data: TABLE-1

No.of obvs.

Armature Voltage(VA) In volts

Speed(n) In r.p.m.

Field Current (If) (Constant) In mA

1

2

3

4

5

6

TABLE-2

No.of obvs.

Field Current (If) In mA

Speed(n) In r.p.m.

Armature Voltage(VA) (Constant) In Volts

1

2

3

4

5

16

Signature of the teacher


17


BASIC EE LABORATORY First / Second Semester Expt.No. 1202-/5

TITLE OF THE EXPT: “NO-LOAD TEST ON SINGLE PHASE

TRANSFORMER” Object: To study the variation of Current, Power and Voltage ratio with applied

voltage of a single-phase transformer at no-load.

Theory : On no-load the power consumed by the transformer is used in providing

its own losses which comprises of (i) Magnetic losses i.e. hysteresis and eddy

current losses in the transformer core. This is also known as “Iron Loss” and is

approximately proportional to the square of the applied voltage. (ii) Resistance

loss in the primary winding due to the no-load current is known as no-load copper

loss. The no-load copper loss is usually very small in comparison to iron losses

and is proportional to the square of the no-load current. As the secondary

winding is open on no-load, there would be no copper loss on the secondary

winding.

The voltage ratio is Vp/Vs and is approximately equal to the ratio of

number of turns in the primary and secondary windings. Where Vp is primary

voltage of the transformer and Vs is the secondary voltage of the transformer.

Procedure : (i) Make connections as shown in the figure and switch on the supply

voltage.

(ii) By adjusting the variac, vary the voltage applied to the transformer

from about 50% to 110% the rated value in about six steps, and in each step

note down the readings of primary voltage, primary current, power input and

secondary voltage. Tabulate the results in the DATA SHEET.

GIVEN DATA : PRIMARY WINDING RESISTANCE IS 0.56 OHMS.

Report : 1. Draw curves to show the variation of –

a) no-load current,

b) voltage ratio and


c) iron loss with applied voltage.

2. Show one sample calculation.

A

PRE

CURRENTCOIL

SECONDARYWINDING

VARIAC

1-PH, 230V, 50Hz A.C.SUPPLY

DOUBLE POLE REWIRABLE SWITCH FUSE UNIT

CIRCUIT DIAGRAM FOR NO-LOAD TEST OF A SINGLE PHASE TRANSFORMER

WATTME

MIA M L

110V

VS VPSSURE

COIL

PRIMARYWINDING

SINGLE PHASE TRANSFORMER

TER

MIVMIV

COM V

FIGURE-1

220V

18


DATA SHEET

“NO-LOAD TEST ON A SINGLE PHASE TRANSFORMER” NAME: ______________________ ROLL NO. ____________ DATE : ____________ Apparatus used:


1 Ammeter MIA

2 Voltmeter MIV

3 Voltmeter MIV

4 Wattmeter ____________V, __________A, p.f=______, Mf =______

W

5 Variac 1-Phase, ________V, ________A, 50Hz VAR

Transformer under test: Primary voltage (Vp): ________________ , Secondary voltage (Vs): _______________ Volt-ampere (VA) :________________ , Phase : __________ , Frequency : 50Hz Experiment Data:

No. of obs

Voltmeter Reading(Vp) in volt

Ammeter reading(I0)in ampere

Power input PI =readingX Mf in watt

Secondary voltage(Vs)in volt

Voltage ratioVp/Vs

Copper loss(Pc)in watt

Iron loss(PI)in watt

1

2

3

4

5

6

* Copper loss (Pc) = I02 X 0.56 watts. 19 Signature of the teacher


BASIC EE EE LABORATORY First/Second Semester Expt.No :1251/6 TITLE : Characteristics of (a) Carbon and Tungsten lamp (b) Fluorescent and CFL. Object: for expt. (a)

To study the volt-ampere, power-voltage and resistance- voltage characteristics of carbon & tungsten Lamp.

for expt.(b) (i) To study the staring method, minimum striking voltage and effect of varying voltage on fluorescent lamp operating from AC supply. (ii) To study the effect of different types of ballast e.g. Aluminum choke, Copper choke and electronic choke on power consumption of Fluorescent lamp. (iii) To find the relative light output of the various lamps on the working area.

Procedure

1. Connect the circuit as shown in fig(i).

: For exp no (a)

2. 3. Set the variac voltage to 100 volt and take down the reading of ammeter and voltmeter.

ENSUTRE ZERO VOLTAGE OUTPUT OF VARIAC BEFORE CONNECTING IT TO THE CIRCUIT.

4. Change the variac output voltage to 230 V AC (rated voltage) in 20 volt step and repeat step 2 at every voltage setting.

5. Measure the luxmeter reading at 230 V for Tungsten lamp on the ambient lighted environment.

6. Repeat the above steps for tungsten as well as carbon filament lamp.

For exp no (b)

1. Connect the Fluorescent lamp according to the circuit diagram in fig(ii). 2. 3. Vary the input voltage by variac and note the voltage at which Fluorescent lamp strikes.

This voltage is known as “Striking voltage”.


4. Note down the reading of the voltmeters, ammeters and wattmeter from striking voltage up to rated voltage 230V in 20 volt steps.

5. Measure the luxmeter reading at 230 V for Fluorescent lamp on the ambient lighted environment.

6. Decrease the applied voltage gradually at which the lamp extinguishes. Note this voltage. This voltage is known as “Extinguishing voltage”.

7. Repeat the above steps for Aluminum choke, Copper choke and electronic choke. 8. Connect the CFL and measure the power consumption and compare with Fluorescent

lamp. 9. Measure the luxmeter reading at 230 V for CFL on the ambient lighted environment.

1. Draw curves of (i) voltage vs. current, (ii) power vs. voltage and (iii) resistance vs. voltage for tungsten and carbon lamp on the same graph paper.

Report:

2. Why the slope of volt –ampere characteristics is increasing in case of tungsten lamp and decreasing in case of Carbon lamp.

3. Plot power Vs voltage curve for each type of choke Fluorescent lamp. 4. Plot power Vs voltage curve for CFL. 5. Comment on the variation of power consumption of fluorescent lamp for different types

of choke. 6. Draw a complete circuit diagram showing how a Fluorescent lamp is to be operated

from DC supply.

CIRCUIT DIAGRAM OF VARIOUS TYPES OF LAMP EXPERIMENT:-

A

Carbon lampV

Tungsten lamp

220V

Fig-1

AM

V

L

C V

Choke/Ballast

V F.L

V

Starter

220V

Fig-2

AM

V

L

C V ElectronicBallast F.L

V220V

Fig-3

AM

V

L

C V ElectronicBallast CFL

220V

Fig-4

Electronic ballast: Electronic ballasts employ inverters to alter mains voltage frequency into high-frequency AC while also regulating the current flow in the lamp. These ballasts take advantage of the higher efficacy of lamps operated with higher-frequency current. Efficacy of a fluorescent lamp rises by almost 10% at a frequency of 10 kHz

, compared to efficacy at normal power frequency.

Block diagram of high frequency ballast

Low pass filter for interference suppression

AC/DC converter

Pre conditioner

DC voltage

DC/AC converter

Lamp controller

High voltage

Lamps

240 VAC 110 VAC

Filter voltage

Ballast controller

http://en.wikipedia.org/wiki/Frequency�

http://en.wikipedia.org/wiki/Alternating_current�

DATA SHEET


PERFORMED BY:………………………………………………………………………………………………………

Date : ………………………………… Roll No: ………………


Sl. No

Apparatus Used :


Lab No.

1 Digital ammeter 2 Digital

voltmeter

3 Digital wattmeter

4 1-ph variac 5 Tungsten

filament lamp

6 Carbon filament lamp

7 Compact Fluorescent lamp

8 Fluorescent lamp

9 Copper E/M choke

10 Aluminum E/M choke

11 Electronic Ballast

12 Starter for Tube lamp

13 Main switch 14 Luxmeter

Experimental Data:

Sl.No

For Tungsten and carbon Filament Lamp

Tungsten filament lamp

Carbon filament lamp

Voltage

Current Power Resistance Voltage Current Power Resistance

Luxmeter reading of tungsten lamp at230 VAC:

Sl.No

For Fluorescent lamp

Type of choke Striking voltage Extinguishing voltage 1 Copper E/M choke 2 Aluminum E/M choke 3 Electronic choke

Sl.No Type of Choke Voltage Current Power Luxmeter

reading Power factor of

the circuit 1

Copper E/M choke

2

Aluminum E/M choke

3

Electronic choke

Sl.No

For CFL Striking voltage: Extinguishing voltage:

Voltage Current Power Luxmeter reading

Power factor of the circuit


Annexure

1. Tube: This is a type of discharge lamp in which the radiation from gas of vapour through which the discharge is passing excites the fluorescent material, suitably placed so that the light emitted by the lamp is that given by this material.

Description of fluorescent lamp assembly

In the fluorescent tube the electrode consists of two parts of electrically connected: (a) the tungsten coil filament coated with mixture of alkaline earth oxides, (b) a metal strip or fin. The ends of the filament at each end are brought out to a cap, the Bi-pin in which two projected pins from the end of the tube. To start discharge in a Fluorescent tube a voltage (about 1000V much larger than the normally available supply voltage (230 V) is required momentarily. For this purpose a choke and a starter is required.

2. Starter: The purpose of starter is to make and then suddenly break the circuit so that there is a large voltage across the fluorescent tube to start the discharge. The common type of starter in use is the glow discharge type. It consists of two metal strips one or both bi-metallic, mounted in a bulb and carrying two contacts which are normally held apart. When the main switch is closed a glow discharge is started between the bi-metal strips. The strips heat up and bent closing the contacts. This short circuits the glow discharge and allows the heating current to flow through the electrodes of the lamp. At the same time the bi-metallic strips begin to cool and presently the contacts open

3. Choke Coil: The choke coil is a coil wound on some magnetic material. The purpose of the choke is two-fold: (a) to give a large voltage momentarily so as to start discharge in the lamp, (b) to allow a certain voltage drop across itself so that the voltage across the lamp is

reduced (in case of AC supply only).

As the starter breaks the circuit, a large voltage is momentarily induced in the choke which starts discharge in the fluorescent tube. Under running condition, the voltage required to continue discharge in the fluorescent tube is small (about 50% of the supply voltage) so that a required amount of voltage is dropped in the choke.

Note :

CFL: A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light, and compact fluorescent tube, is a

In case of DC supply no voltage is dropped in the choke. The required amount of voltage is dropped in a resistance which is added in series with the choke in the circuit.

fluorescent lamp designed to replace an incandescent lamp; some types fit into light fixtures formerly used for incandescent lamps. The lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

Compared to general-service incandescent lamps giving the same amount of visible light, CFLs use one-fifth to one-third the electric power, and last eight to fifteen times longer. A CFL has a higher purchase price than an incandescent lamp, but can save over five times its purchase price

http://en.wikipedia.org/wiki/Fluorescent_lamp�

http://en.wikipedia.org/wiki/Incandescent_light_bulb�



http://en.wikipedia.org/wiki/Light_fixture�

http://en.wikipedia.org/wiki/Electronic_ballast�

http://en.wikipedia.org/wiki/Luminous_flux�

in electricity costs over the lamp's lifetime. Like all fluorescent lamps, CFLs contain mercury, which complicates their disposal. In many countries, governments have established recycling schemes for CFLs and glass generally.

CFLs radiate a spectral power distribution that is different from that of incandescent lamps. Improved phosphor formulations have improved the perceived colour of the light emitted by CFLs, such that some sources rate the best "soft white" CFLs as subjectively similar in colour to standard incandescent lamps.

The CFL comes in two categories:

(a) Retrofit: It can directly replace ordinary incandescent bulbs. GLS 40W 60W 75W 100W CFL 9W 11W 15W 20W The CFL has 10000 burning hours in comparison GLS, which has 1000 burning hours and saves 80% energy w.r.t a normal GLS lamp(refer above table).

(b) Non- retrofit: It requires special luminaries with built-in ballast and is suitable for new light points. The use of electronic gear (ballast, ignitor, capacitor) can offer the possibility of controllable light output (dimming), high frequency operation and independence from the supply system. It is therefore possible to use both AC and DC supply and a wider of supply voltages. The electronic choke also consumes less power; provides fast flicker free starting and no stroboscopic effect.

(c) The electronic gear is to be used both for CFLs and ordinary fluorescent lamps for maximum utilization of the benefits mentioned. The comparison between electronic ballast and electromagnetic ballast is done and the considerable energy savings pointed out.

Lamp Type Fluorescent lamp with E/M choke (36w)

Fluorescent lamp with Electronic choke

Nominal lamp consumption 36W 32W Ballast loss 12.5W 5W

System consumption 48.5W 37W

% saving = (48.5-37)/48.5=23.7%

http://en.wikipedia.org/wiki/Mercury_%28element%29�

http://en.wikipedia.org/wiki/Color_temperature#Spectral_power_distribution�

http://en.wikipedia.org/wiki/Phosphor�

DEPARTMENT OF ELECTRICAL ENGINEERING

BENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR BASIC EE LABORATORY First/Second Semester Expt.No. 1251/7 TITLE : Verification of three phase relationship. Object: i). To verify the relationships between line quantities and phase quantities (voltage and current) for a balance three phase ,three wire (a)star connected (b) delta connected load. Theory:

Star connected load A three phase star connected load is an open network consisting of at least three resistances with one terminal of each connected together at a common point (also known as star point), remaining with three terminals being left open for connection to external circuit.

Three phase star connected load . If the values of the resistances are equal (i.e. R1= R2=R3), the three phase load is balanced. R1= R2=R3 (for balanced 3-ph load) L-L voltage =V1 2 =V2 3 =V3 1 =VL (for balanced 3-ph supply) Phase voltage =V1 N =V2N =V3N =Vph (for balanced 3-ph supply) I1, I2, I3 are line currents and phase currents (assumed positive)

1, 2, 3 are line terminals of 3

phase supply connected to 3- ph

balanced load and N is the star

point

Three phase delta connected load If the values of the resistances are equal (i.e. R

Delta connected load A three phase delta connected load is a closed network consisting of at least three resistances, each of them being connected between a separate pair of terminals, the said terminals being available for connection to external circuit.

1= R2=R3), the three phase load is balanced. R1= R2=R3 (for balanced 3-ph load) V1 2 =V23 =V3 1 =VL = VPH (for balanced 3-ph supply) I1, I2, I3 are line currents(assumed positive) I12, I23, I31 are phase currents currents Procedure:

1. Make the circuit connection as shown in fig(i)

For star connection

2. Identify the FIXED RESISTANCE TERMINALS position of each rheostat and set them at this position.

3. Connect three terminals of star connected load to three phase variac output terminal.

4. Switch on the mains and set variac output to 100V.Note the readings of three ammeters, voltage between 1 and 2, 2 and 3, 3 and 1; also voltages between 1 and N, 2 andN, 3 and N .


5. Gradually increase the variac output and set it to 150 V, 200 V. 6. Repeat step 4 and check the relationships between VL and Vph, IL and Iph

for each reading and complete the table.

1. Make the circuit connection as shown in fig(ii).

For delta connection

2. Repeat step 2 and 3 stated above. 3. Switch on the mains and set variac output to 100V.Note the readings of ammeters,

voltage between 1 and 2, 2 and 3, 3 and 1. 4. Gradually increase the variac output and set it to 150 V, 200 V.

5. Repeat step 4 and check the relationships between VL and Vph, IL and Iph

Report:

for each reading and complete the table.

1. What is meant by phase sequence of 3-ph supply? 2. Is it possible to form a balanced star connected or delta connected load using (i) pure

inductance (ii) pure capacitance (ii) R-L series combination (iv) R-C series combination in each branch of the load.

3. Draw phasor diagram for the following (a) Balanced star connected load with pure resistance. (b) Balanced delta connected load with pure resistance.

4. Calculate the phase angle between the line voltage V12 and the phase current I23

5. A 400 V, 3-ph 4 wire distribution system has a balanced load of 2.3 KW in each phase. Calculate neutral current.

in a delta connected system when the load p.f is 1/√2 leading, assume supply phase sequence to be RYB.

6. In Q4 above, if two supply lines are switched off, calculate neutral current if p.f is unity. 7. A 3-ph delta connected load consumes a total power of 3KW.

A 3-ph 400 V star connected load consumes a total power of 3 KW. Assuming unity p.f load, calculate phase current, line current, phase voltage, line voltage in both cases .Calculate the power consumed and the load resistance per phase in both the cases.


PERFORMED BY:………………………………………………………………………………………………………

Date : ………………………………… Roll No: ………………


Sl. No

Apparatus Used :


Lab No.

1 Digital ammeter

2 Digital voltmeter

3

Resistance

4 3-ph variac

5 Main switch

Sl. No

Experimental Data:

Type of

connection Observation Calculation

Line Voltage (VL

Phase voltage ( V) ph

Line Current (I) L

Phase current(I) ph

V)

L / V Iph L / Iph

1

2

3

1

2

3


Documents

Lab Manual - 1st Semester & 2nd Semester