DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR

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1 JEE-Lab(EE-1202)/PBC/05 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY Expt.No.1202-/1(a) First/ Second Semester FAMILIARISATION EXPERIMENT (ARIAC, POTENTIAL DIIDER, MC, MI, MCA, MIA) Object : 1. To become familiar with POTENTIAL DIIDER and ARIAC 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 DIIDER 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 R 1 + R 2 = resistance between the input terminals of the potential divider, when no current is flowing through the output circuit I 1 1 = R1 + R 2 o = I1.R 2 = 1 = R 2 R1 + R 2 1

2 JEE-Lab(EE-1202)/PBC/05 Procedure: i) Connect MCA and MIA in series and MC and MI 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. ary 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 MC and MI are reversed, in Table II of the Data Sheet. THEORY : II ARIAC 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) ary 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 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 JEE-Lab(EE-1202)/PBC/05 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 No. of Readings of Obvs. MCA MIA MC MI Remarks TABLE II METER Normal Connection Reversed Connections MCA MIA MC MI 3

4 JEE-Lab(EE-1202)/PBC/05 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING & SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY First/ Second Semester Expt.No /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 125/150. (ii) Adjust the variac output voltage to 125/150 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 250/300 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 125/150 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. 4

5 JEE-Lab(EE-1202)/PBC/05 Report : 1) Calculate multiplying factors from the current and voltage ranges used. When power factor is unity, oltage 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? CIRCUIT DIAGRAM FOR FAMILIARIZATION OF WATTMETER 1-PH., 230, 50 Hz A.C.SUPPLY DOUBLE POLE REWIRABLE SWITCH FUSE UNIT MIA A PRESSURE COIL A COM L CURRENT COIL L O A D ARIAC WATTMETER FIGURE-1 5

6 JEE-Lab(EE-1202)/PBC/05 DATA SHEET FAMILIARIZATION OF WATTMETER NAME: Apparatus used: ROLL NO. DATE : Sl. No. Item Range Lab. No. 1 Ammeter MIA 2 Wattmeter, A, p.f=, M f W 3 ariac 1-Phase,, A, 50H z AR Experiment Data: No.of obvs. 1 Current range TABLE-1 Wattmeter oltage range reading Multiplying factor(m f ) Power No.of obvs Item TABLE-2 Current coil terminal M connected to Pressure coil. Terminal COM as in fig.-1 Current coil reversed, pressure coil as in fig.-1 Current coil as in fig.-1 but pressure coil is reversed. Deflection (Indicate positive or negative) 4 Both current and pressure coil is reversed. Signature of the teacher 6

7 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY First/Second Semester Expt.No /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 R L (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 E th in series with a resistance R th where E th is the voltage across the terminals a-b when they are open circuited and R th 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 R L and source resistance R S is given by I= / (R L + R S ) Where is the applied voltage. So, the power P absorbed in the resistance R L is P= [/ (R L + R S )] 2 R L The value of R L for which P will be maximum is obtained from the relation when R L = R S Hence for maximum power transfer to the load, the load resistance (R L ) must be equal to the source resistance (R S ).

8 Procedure: For Superposition Theorem: 1. Make connections as shown in the diagram. 2. Measure the current through R L when both sources ( 1 & 2 ) are present and tabulate in Table Keeping one voltage source (1) in the circuit and other voltage source ( 2 ) replaced by their internal resistance (here assume zero) note down the ammeter reading in Table -1 with proper polarity. 4. Now insert the other source (2) in the circuit removing the voltage source ( 1 ) by their internal resistance (here assume zero) and measure the circuit current with proper polarity. For Thevenin s Theorem: 1. Remove the resistance R L and measure the open circuit voltage ( th ) across a&b and tabulate in table II. 2. Measure the resistance Rth of the circuit across a&b when the two sources are replaced by their internal resistance. The resistance R th is measured across a and b by drop method (i.e either 1 or 2 is connected across a and b and measure ammeter current. Then R th = 1 or 2 /ammeter current). 3. IL = th /R th + RL 4. Tabulate I in table II 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 R S. 3. Increase RL ohm maximum and measure supply voltage (), voltage across the load resistance ( RL ), voltage across the source resistance ( RS ) and the current through the circuit and tabulate the data. 4. Keeping the supply voltage fixed, lower the load resistance (RL) in another five steps and tabulates the results for different values of current. Report: 1. (a) How will you represent ideal voltage and current sources? (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 RS vs. I in a graph paper and determine the values of the source resistance (R S ). 4. Plot P vs. RL in a graph paper and determine the value of R L for which P is maximum. Hence compare this with R S obtained in (2)

9 CIRCUIT DIAGRAM OF NETWORK THEOREM EXPERIMENT:- 40Ω a 50Ω R L = 6Ω 10 A b 14 Fig-1 RS R s = 30 Constant R L = RL Fig-2

10 DATA SHEET TITLE OF THE EXPERIMENT:.. PERFORMED BY: Date : Roll No: Experiment No :. Apparatus Used : Sl. No Item Quantity Range /Rating Maker s Name 1 Digital ammeter 2 Digital voltmeter 3 Resistance Lab No. 4 DC regulated power supply 5 Main switch Experimental Data: Table-1 Sl.No Particular 1 Current through R L with both the sources present(i) 2 Current through R for source 1 only(i 1 ) Current through R L for source 2 only(i 2 ) 5 Algebraic sum of I 1 and I 2 Current/voltage Table-II Sl.No Particulars oltage / current / resistance 1 oltage across a and b when R L is removed(v OC ) 2 Ammeter current 3 Equivalent resistance( R eq ) 4 Load current(i L )

11 Table-III No. of Obvs. Supply voltage () volt oltage across ( RS ) olt oltage across (RL) olt Current (I) Amp alue of R Ohm L Power consumed in RL (P) Watt Signature of the Teacher

12 JEE-Lab(EE-1202)/PBC/05 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING & SCIENCE UNIERSITY, SHIBPUR BASIC EE Expt. No. 1202/3 First / Second Semester 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 R L and an inductance L in series, so that at any frequency f, the impedance of the choke Z=(R L 2 +X L 2 ) ½, where, X L =2π fl.} 2) Measure Power, Current and oltage for two values of current between 0.7 and 1.1A (Adjust by means of the rheostat R 1 ) to complete TABLE-1 of the DATA SHEET. Report : 1) Complete TABLE-1of the DATA SHEET to find R L, L and Power factor of the choke. 2) For one value of current, of TABLE-1of the DATA SHEET, calculate IR L and IX L. 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 R 1 ), measure Power, Current and oltage to complete TABLE. Report: 5) For one value of current from the observed data, calculate for value of R L, L and C previously determined. 6) On a square paper, draw the phasor diagram to scale following the procedure given below:- 1) Draw phasor R and c (fig.-5) and find. 2) Draw phasor L knowing -----? as determined before. 3) Find =( L + Rf + C ) and hence the magnitude of and Cosø. 4) Complete TABLE-3 of the DATA SHEET. 10

13 JEE-Lab(EE-1202)/PBC/05 STUDY OF A.C. SERIES CIRCUIT DATA SHEET NAME: ROLL NO.: DATE : Apparatus used: Sl. Item Range Lab. No. No. 1. Ammeter MIA 2. oltmeter MI 3. Wattmeter, A, p.f=, M f = W Experiment Data: TABLE-1 No.of Observed data Calculated data obvs. I W Z=/I R L L p.f.=w/i Power factor from phasor diagram 1 2 TABLE-2 Observed data Calculated data No.of obvs. P.F= I W Z=/I R C C W / I 1 2 Power factor from phasor diagram TABLE-3 No.of Observed data Calculated power factor obvs. I Rf W Cosø From phasor diagram from Phasor diagram Signature of the teacher

14 JEE-Lab(EE-1202)/PBC/05 CIRCUIT & PHASOR DIAGRAM FOR STUDY OF A.C. SERIES CIRCUIT L O I C FIGURE-1 FIGURE-2 PHASOR DIAGRAM DOUBLE POLE REWIRABLE SWITCH FUSE UNIT RHEOSTAT CURRENT COIL 1-PH, 230, A.C.SUPPLY 50 Hz PRESSURE COIL COM M L A MIA MI R L C WATTMETER CHOKE COIL FIGURE-3 CIRCUIT DIAGRAM 11

15 JEE-Lab(EE-1202)/PBC/05 CIRCUIT & PHASOR DIAGRAM FOR STUDY OF A.C. SERIES CIRCUIT = L + RC + C Rf I C Rf + C 1-PH, 230, 50 Hz A.C.SUPPLY FIGURE-4 PHASOR DIAGRAM DOUBLE POLE REWIRABLE SWITCH FUSE UNIT CURRENT COIL PRESSURE COIL CHOKE COIL M L R f R L C COM RHEOSTAT MI Rf MI CAPACITOR MIA A WATTMETER FIGURE-5 CIRCUIT DIAGRAM 12

16 JEE-Lab(EE-1202)/PBC/05 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING & SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY Expt.No /4 First / Second Semester 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 across the armature terminals of a d.c. Shunt Motor is approximately related as : = KØn; Where, Ø is the flux per pole and is proportional to field current (I f ). n is the speed of the motor. K is a constant of the motor. A) By varying the armature voltage ( A ), keeping the field current (I f ) constant, speed variation from zero to about rated value can be obtained. B) By varying the field current (I f ),keeping armature voltage( A ) 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 I f ),and the potential divider in the minimum voltage position (=0) switch on the d.c. 220 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 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 (I f ). Observe that the speed increases. Note field current (I f ), speed (n) and armature voltage (). 14

17 JEE-Lab(EE-1202)/PBC/05 6) Decrease field current (I f ) 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 ( A ), with field current (I f ) constant. b) Speed (n) versus field current (I f ), with armature voltage ( A ) constant. CIRCUIT DIAGRAM FOR SPEED CONTROL OF D.C. SHUNT MOTOR 220, D.C.SUPPLY DOUBLE POLE REWIRABLE SWITCH FUSE UNIT ROTATING ARMATURE A 1 SHUNT FIELD WINDING MC M SH 1 SH 2 POTENTIAL DIIDER A 2 A MCA RHEOSTAT FIGURE-1 15

18 JEE-Lab(EE-1202)/PBC/05 DATA SHEET SPEED CONTROL OF D.C. SHUNT MOTOR NAME: ROLL NO. DATE : Apparatus used: Sl. No. Item Range Lab. No. 1. Ammeter MCA 2. oltmeter MC 3. Tachometer Machine under test: D.C. Shunt Motor oltage ():, Power:, Current: Speed:, Lab. No. Experiment Data: No.of obvs Armature oltage( A ) In volts TABLE-1 Speed(n) In r.p.m. Field Current (I f ) (Constant) In ma No.of obvs. 1 Field Current (I f ) In ma TABLE-2 Speed(n) In r.p.m. Armature oltage( A ) (Constant) In olts Signature of the teacher

19 JEE-Lab(EE-1202)/PBC/05 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING & SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY Expt.No /5 First / Second Semester TITLE OF THE EXPT: NO-LOAD TEST ON SINGLE PHASE TRANSFORMER Object: To study the variation of Current, Power and oltage 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 p / s and is approximately equal to the ratio of number of turns in the primary and secondary windings. Where p is primary voltage of the transformer and s 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. GIEN 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 17

20 JEE-Lab(EE-1202)/PBC/05 c) iron loss with applied voltage. 2. Show one sample calculation. CIRCUIT DIAGRAM FOR NO-LOAD TEST OF A SINGLE PHASE TRANSFORMER 1-PH, 230, 50Hz A.C.SUPPLY DOUBLE POLE REWIRABLE SWITCH FUSE UNIT CURRENT COIL SECONDARY WINDING MIA A M COM PRESSURE COIL L MI P 220 MI 110 S ARIAC WATTMETER PRIMARY WINDING SINGLE PHASE TRANSFORMER FIGURE-1 18

21 JEE-Lab(EE-1202)/PBC/05 DATA SHEET NO-LOAD TEST ON A SINGLE PHASE TRANSFORMER NAME: ROLL NO. DATE : Apparatus used: Sl. Item Range Lab. No. No. 1 Ammeter MIA 2 oltmeter MI 3 oltmeter MI 4 Wattmeter, A, p.f=, M f = 5 ariac 1-Phase,, A, 50Hz AR W Transformer under test: Primary voltage ( p ):, Secondary voltage ( s ): olt-ampere (A) :, Phase :, Frequency : 50Hz Experiment Data: No. of obs oltmeter Reading( p ) in volt Ammeter reading(i 0 ) in ampere Power input P I =readingx M f in watt Secondary voltage( s ) in volt oltage ratio p / s Copper loss(p c ) in watt Iron loss(p I ) in watt * Copper loss (P c ) = I 0 2 X 0.56 watts. 19 Signature of the teacher

22 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIERSITY, SHIBPUR 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: For exp no (a) 1. Connect the circuit as shown in fig(i). 2. ENSUTRE ZERO OLTAGE OUTPUT OF ARIAC BEFORE CONNECTING IT TO THE CIRCUIT. 3. Set the variac voltage to 100 volt and take down the reading of ammeter and voltmeter. 4. Change the variac output voltage to 230 AC (rated voltage) in 20 volt step and repeat step 2 at every voltage setting. 5. Measure the luxmeter reading at 230 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. ENSUTRE ZERO OLTAGE OUTPUT OF ARIAC BEFORE CONNECTING IT TO THE CIRCUIT. 3. ary 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 230 in 20 volt steps. 5. Measure the luxmeter reading at 230 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.

23 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 for CFL on the ambient lighted environment. Report: 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. 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 s voltage curve for each type of choke Fluorescent lamp. 4. Plot power s 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.

24 CIRCUIT DIAGRAM OF ARIOUS TYPES OF LAMP EXPERIMENT:- A Carbon lamp Tungsten lamp 220 Fig-1 A M L Choke/Ballast C F.L Starter 220 Fig-2 A C M L Electronic Ballast F.L 220 Fig-3 A C M L Electronic Ballast CFL 220 Fig-4

25 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. 240 AC 110 AC Low pass filter for interference suppression Filter voltage AC/DC converter Pre conditioner DC voltage DC/AC converter Lamp controller High voltage Lamps Ballast controller Block diagram of high frequency ballast

26 DATA SHEET TITLE OF THE EXPERIMENT:.. PERFORMED BY: Date : Roll No: Experiment No :. Apparatus Used : Sl. No Item Quantity Range /Rating Maker s Name 1 Digital ammeter 2 Digital voltmeter Lab No. 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

27 Experimental Data: For Tungsten and carbon Filament Lamp Sl. No Tungsten filament lamp Carbon filament lamp oltage Current Power Resistance oltage Current Power Resistance Luxmeter reading of tungsten lamp at230 AC: For Fluorescent lamp Sl.No Type of choke Striking voltage Extinguishing voltage 1 Copper E/M choke 2 Aluminum E/M choke 3 Electronic choke

28 Sl.No Type of Choke oltage Current Power Luxmeter reading Power factor of the circuit 1 Copper E/M choke 2 Aluminum E/M choke 3 Electronic choke For CFL Striking voltage: Extinguishing voltage: Sl.No oltage Current Power Luxmeter reading Power factor of the circuit Signature of the Teacher

29 Annexure Description of fluorescent lamp assembly 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. 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 1000 much larger than the normally available supply voltage (230 ) 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 : 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. CFL: A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light, and compact fluorescent tube, is a 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

30 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 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=23.7%

31 DEPARTMENT OF ELECTRICAL ENGINEERING BENGAL ENGINEERING AND SCIENCE UNIERSITY, SHIBPUR BASIC EE LABORATORY First/Second Semester Expt.No. 1251/7 TITLE : erification 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. 1, 2, 3 are line terminals of 3 phase supply connected to 3- ph balanced load and N is the star point. Three phase star connected load If the values of the resistances are equal (i.e. R 1 = R2=R3), the three phase load is balanced. R 1 = R2=R3 (for balanced 3-ph load) L-L voltage = 1 2 = 2 3 = 3 1 = L (for balanced 3-ph supply) Phase voltage = 1 N = 2N = 3N = ph ( for balanced 3-ph supply) I 1, I 2, I 3 are line currents and phase currents (assumed positive)

32 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. Three phase delta connected load If the values of the resistances are equal (i.e. R1= R2=R3), the three phase load is balanced. R 1 = R2=R3 (for balanced 3-ph load) 1 2 = 23 = 3 1 = L = PH (for balanced 3-ph supply) I 1, I 2, I 3 are line currents(assumed positive) I 12, I 23, I 31 are phase currents currents Procedure: For star connection 1. Make the circuit connection as shown in fig(i) 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. ENSUTRE ZERO OLTAGE OUTPUT OF ARIAC BEFORE CONNECTING IT TO THE CIRCUIT. 4. Switch on the mains and set variac output to 100.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, Repeat step 4 and check the relationships between L and ph, I L and I ph for each reading and complete the table. For delta connection 1. Make the circuit connection as shown in fig(ii). 2. Repeat step 2 and 3 stated above. 3. Switch on the mains and set variac output to 100.Note the readings of ammeters, voltage between 1 and 2, 2 and 3, 3 and Gradually increase the variac output and set it to 150, 200.

33 5. Repeat step 4 and check the relationships between L and ph, I L and I ph for each reading and complete the table. Report: 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 12 and the phase current I 23 in a delta connected system when the load p.f is 1/ 2 leading, assume supply phase sequence to be RYB. 5. A 400, 3-ph 4 wire distribution system has a balanced load of 2.3 KW in each phase. Calculate neutral current. 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 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.

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35 TITLE OF THE EXPERIMENT:.. PERFORMED BY: Date : Roll No: Experiment No :. Apparatus Used : Sl. No Item Quantity Range /Rating Maker s Name 1 Digital ammeter 2 Digital voltmeter 3 Resistance Lab No. 4 3-ph variac 5 Main switch Experimental Data: Sl. No 1 Type of connection Line oltage ( L Phase voltage ( Observation Line Current (I Phase current(i ) ph) L) ph ) Calculation L / ph IL / I ph Signature of the Teacher