ELECTRICAL MACHINES LABORATORY 1 Lab Manual

Transcription

1 Channabasaveshwara Institute of Technology (An ISO 90:25 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur Karnataka. QMP 7.1 D/F Department of Electrical & Electronics Engineering ELECTRICAL MACHINES LABORATORY 1 Lab Manual 15EEL37 B.E - III Semester Lab Manual Name : USN : Batch : Section :

2 Channabasaveshwara Institute of Technology (An ISO 90:25 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur Karnataka. Department of Electrical & Electronics Engineering ELECTRICAL MACHINES LABORATORY 1 Lab Manual Version 2.0 August 27 Prepared by: Reviewed by: 1. Murugesh P D V C Kumar Assistant Professor Professor 2. Praveen M G Assistant Professor Approved by: V C Kumar Professor & Head Dept. of EEE

3 ELECTRICAL MACHINES LABORATORY 1 Sub Code: 15EEL37 IA Marks: 20 Hrs/week: 03 Exam Hours: 03 Total Hours: 42 Exam Marks: Open Circuit and Short circuit tests on single phase step up or step down transformer and predetermination of (i) Efficiency and regulation. (ii) Calculation of parameters of equivalent circuit. 2. Sumpner s test on similar transformers and determination of combined and individual transformer efficiency. 3. Parallel operation of two dissimilar single-phase transformers of different kva and determination of load sharing and analytical verification given the Short circuit test data. 4. Polarity test and connection of 3 single-phase transformers in star delta, delta-delta and V-V (Open delta) and determination of efficiency and regulation under balanced resistive load. 5. Scott connection with balanced and unbalanced loads. 6. Separation of hysteresis and eddy current losses in single phase transformer. 7. No load and load characteristics of DC shunt generator. 8. Voltage regulation of an alternator by EMF and MMF methods. 9. Voltage regulation of an alternator by ZPF method. 10. Slip test Measurement of direct and quadrature axis reactance and predetermination of regulation of salient pole synchronous machines. 11. Performance of synchronous generator connected to infinite bus, under constant power and variable excitation & vice - versa. 12. Power angle curve of synchronous generator.

4 Channabasaveshwara Institute of Technology (An ISO 90:25 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur Karnataka. DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING VISION: To be a department of excellence in electrical and electronics Engineering education and Research, thereby to provide technically competent and ethical professionals to serve the society. MISSION: To provide high quality technical and professionally relevant education in the field of electrical engineering. To prepare the next generation of electrically skilled professionals to successfully compete in the diverse global market. To nurture their creative ideas through research activities. To promote research and development in electrical technology and management for the benefit of the society. To provide right ambience and opportunities for the students to develop into creative, talented and globally competent professionals in electrical sector.

5 Channabasaveshwara Institute of Technology (An ISO 90:25 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur Karnataka. OUR VISION To create centers of excellence in education and to serve the society by enhancing the quality of life through value based professional leadership. OUR MISSION To provide high quality technical and professionally relevant education in a diverse learning environment. To provide the values that prepare students to lead their lives with personal integrity, professional ethics and civic responsibility in a global society. To prepare the next generation of skilled professionals to successfully compete in the diverse global market. To promote a campus environment that welcomes and honors women and men of all races, creeds and cultures, values and intellectual curiosity, pursuit of knowledge and academic integrity and freedom. To offer a wide variety of off-campus education and training programmes to individuals and groups. To stimulate collaborative efforts with industry, universities, government and professional societies. To facilitate public understanding of technical issues and achieve excellence in the operations of the institute.

6 INDEX PAGE Sl. No. Name of the Experiment Conduction Date Repetition Submission of Record Manual Marks (Max. 20) Record Marks (Max. 10) Signature (Student) Signature (Faculty) Average Note: If the student fails to attend the regular lab, the experiment has to be completed in the same week. Then the manual/observation and record will be evaluated for 50% of maximum marks.

7 Course objectives & outcomes Course objectives: 1. Conducting of different tests on transformers and synchronous machine and evaluation of their performance. 2. Verify the parallel operation of two single phase transformers of different KVA rating. 3. Study the connection of single phase transformers for three phase operation and phase conversion. 4. Study of synchronous generator connected to infinite bus. Course outcomes: At the end of the course the student will be able to: 1. Conduct different tests on transformers and synchronous generators and evaluate their performance. 2. Connect and operate two single phase transformers of different KVA rating in parallel. 3. Connect single phase transformers for three phase operation and phase conversion. 4. Assess the performance of synchronous generator connected to infinite bus.

8 1. Do not play with electricity. Caution 2. Carelessness not only destroys the valuable equipment in the lab but also costs your life. 3. Mere conductivity of the experiment without a clear knowledge of the theory is of no value. 4. Before you close a switch, think of the consequences. 5. Do not close the switch until the faculty in charge checks the circuit.

9 General Instructions to Students 1. Students should come with thorough preparation for the experiment to be conducted. 2. Students will not be permitted to attend the laboratory unless they bring the practical record fully completed in all respects pertaining to the experiment conducted in the previous class. 3. Name plate details including the serial number of the machine used for the experiment should be invariably recorded. 4. Experiment should be started only after the staff-in-charge has checked the circuit diagram. 5. All the calculations should be made in the observation book. Specimen calculations for one set of readings have to be shown in the practical record. 6. Wherever graphs are to be drawn, A-4 size graphs only should be used and the same should be firmly attached to the practical record. 7. Practical record should be neatly maintained. 8. They should obtain the signature of the staff-in-charge in the observation book after completing each experiment. 9. Theory regarding each experiment should be written in the practical record before procedure in your own words. 10. Come prepared to the lab with relevant theory about the Experiment you are conducting. 11. Before doing the circuit connection, check the active components, equipments etc, for their good working condition. 12. Do not use the multimeter, if the battery indication is low.

10 Expt. No. Channabasaveshwara Institute of Technology (An ISO 90:25 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur Karnataka. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGG. CONTENTS First Cycle Experiments Title of the Experiment 1 Regulation of Alternator by ZPF Method OC & SC Tests on 1-Ф Transformer Slip Test on Alternator Scott Connection Separation of hysteresis and eddy current losses in single phase transformer No-Load and Load characteristics of a DC - shunt generator Polarity test on 1-ф transformer. 30 Second Cycle Experiments Page No. Expt. No. 8 Title of the Experiment Polarity Test and connection of 3 single-phase transformers in star delta, delta delta and V V (open-delta) connection under load. Page No Sumpner s Test Performance of synchronous generator connected to infinite bus, under constant power and variable excitation & vice - versa Regulation of Alternator by EMF and MMF Method Parallel Operation of Two 1-Ф Transformers Power angle curve of synchronous generator. 60 Question bank. 65 Viva - voce Questions. 67 References. 69 Appendix. 70

11 CIRCUIT DIAGRAM: Tabular Column 1. Open Circuit Test 2. Short Circuit Test Sl. No I f Amps V L V 0 Volts V ph I f Amps I SC Amps

12 Experiment No. REGULATION OF ALTERNATOR BY ZPF METHOD Date: / / Aim To determine the percentage regulation of an alternator by ZPF method or Potier Triangle Method. Apparatus Required Sl. No Particulars Range Type Quantity. Voltmeter V MI 02. Ammeters 03. Rheostats 04. Watt meters 0-10/20A 0-1/2A 0-750Ω,1.2A 0-38Ω,8.5A 0 10/20 A, V MI MC - 02 LPF Tachometer phase Inductive Load - - Procedure a. Open Circuit Test 1. Connections are made as shown in the circuit diagram (1.a) 2. Keeping the rheostat R 1 in the field circuit of motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in field circuit of the alternator in cut-in positions, and TPST (S 2 ) in open position, the supply switch (S 1 ) is closed. 3. The motor is brought to synchronous speed by cutting out the rheostat R 2 and then by cutting in the rheostat R 1, if necessary. 4. By gradually cutting out the rheostat R 3, the readings of ammeter (A 1, 0-2A) and voltmeter (V) are noted down. 5. The above step is continued until voltmeter reads about 1.25 times the rated voltage of the alternator. a. Short Circuit Test 1. The rheostat R 3 is brought to its initial position (cut-in) and TPST (S 2 ) is closed. 2. By gradually cutting out the rheostat R 3, reading of the ammeter (A 2, 0-10/20A) is adjusted to the rated current of the alternator and the corresponding field current (A 1, 0-1/2A) is noted down. 3. All the rheostats are brought back to their respective initial positions, TPST switch (S 2 ) and supply switch (S 1 ) are opened. Dept. of EEE, CIT-Gubbi, Page No.2

13 3. ZPF Test Sl. No. I 1 Ampere I f Ampere W 1 Watt W 2 Watt V Volt

14 b. ZPF Test 1. Connections are made as shown in the circuit diagram (1.b) 2. Keeping the rheostat R 1 in the field circuit of the motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in the field circuit of the generator in cut-in position, the supply switch (S 1 ) is closed. 3. The motor is brought to its rated speed by cutting out the rheostat R 2 and Cutting in the rheostat R 1, if necessary. 4. The alternator voltage is built up to its rated value by gradually cutting out the rheostat R The TPST (S 2 ) is closed and vary the inductive load up to the rated current of the Alternator. The readings of all the meters are noted down. 6. The load is gradually removed, the TPST switch (S 2 ) is opened and all Rheostats are brought back to their respective initial positions then the supply switch (S 1 ) is opened. c. Construction of Potier Triangle 1. Draw OCC and SCC for suitable scales. 2. A tangent drawn to OCC curve represents the air gap line. 3. Point B is obtained from ZPF test, which indicates the full load current for a particular field current I f value when power consumed by load is zero. 4. Point A is marked on X-axis such that OA represents the field current required to drive full load current at short circuit condition. It is equal and opposite to the demagnetizing armature reaction and balancing leakage reactance drop at full load. 5. Points A and B are joined to get ZPF curve which is parallel to OCC curve. 6. From point B a point H is marked such that BH=OA. 7. From point H a line HD is drawn parallel to the tangent such that it cuts OCC curve at point D. 8. Join DB. Now triangle BHD is known as Potier Triangle. 9. A perpendicular line DF is drawn, which represents the armature voltage drop (IX L ) due to armature leakage reactance. Dept. of EEE, CIT-Gubbi, Page No.4

15 Model Graph d. Determination of No-Load EMF (E o ) 1. From point D, perpendicular line is drawn to X-axis and horizontal line to Y-axis to locate point G and E respectively. DG is measured on Y-axis, which represents E and field current corresponding to E is OG. 2. A line NA is drawn such that NA=BF, which represents the field current required to overcome armature reaction. 3. NA is added to OG as in case of MMF method. GM is marked such that GM=NA at an angle (90+ Ф) from point G. Now points O & M are joined, which represents the resultant excitation required to generate no-load EMF E o. 4. With O as center, OM as radius an arc is drawn which cuts X-axis at point P. 5. From point P a vertical line is drawn to X-axis such that it cuts OCC at a point Q. It is extended to Y-axis, measures E o volts, Therefore Eo V Regulation %R= * 100 where V = voltage / phase, volt V e. Determination of Resultant Field Current (I fr ) 1. BF is measured, which gives field current I f1, ampere. 2. DF is measured, which gives Reactive drop IX L, volt. 3. Considering lagging power factor, E = ((V cosф) 2 + (V sinф + IX L ) 2 ) Volt Where V= voltage/ phase, volt. a. I= rated current, ampere. This value is measured on Y-axis. 4. A line from point E is extended to OCC such that OR is located which gives I f2.

16 Therefore resultant field current is given by I fr = (I f2 2 + I f I f1 I f2 cosө) Ampere. CALCULATION: Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.6

17 CIRCUIT DIAGRAM:

18 Experiment No. 02 Date: / / OPEN CIRCUIT (OC) & SHORT CIRCUIT (SC) TEST ON 1-Ф TRANSFORMER AIM: By conducting Open circuit and Short Circuit tests on a given 1-Ф transformer to predetermine efficiency, voltage regulation and to draw its equivalent circuit. APPARATUS REQUIRED: PROCEDURE: 1. OPEN CIRCUIT TEST Sl. No Particulars. Range Type Quantity. Voltmeter 02 Ammeter. 03. Wattmeter V 0-30V 0-2A 0-10/20A MI MI MI MI 2A,300V LPF 10/20A,75V UPF 1. Connections are made as shown in the circuit diagram (2.a). 2. By keeping auto-transformer voltage in zero out-put position, the supply switch (S 1 ) is closed. 3. Vary the auto transformer voltage gradually and apply rated voltage to the LV side of the transformer and keep the HV side open. 4. The readings of all the meters are noted down. 5. The auto-transformer is brought back to its initial zero output position, the supply switch (S 1 ) is opened. 2. SHORT CIRCUIT TEST 1. Connections are made as shown in the circuit diagram (2.b). 2. Keeping auto-transformer voltage in zero out-put position, the supply switch (S 1 ) is closed. 3. By varying the 1-Ф auto transformer, a low voltage is applied to HV side of the transformer such that the rated current flows through it and short the LV side of the transformer. 4. The Primary rated current is given by : I 1 = (kva * 1000) / Rated Primary voltage (V 1 ). 5. The readings of all the meters are noted down. 6. The auto-transformer is brought back to its initial zero output position, the supply switch (S 1 ) is opened. Dept. of EEE, CIT-Gubbi, Page No.8

19 TABULAR COLUMN: 1. OPEN CIRCUIT TEST Sl. No V O (Volts) I O (Amps) W O (Watt) 2. SHORT CIRCUIT TEST Sl. No V SC (Volts) I SC (Amps) W sc (Watt) (Vsel Isel Cos ) NOTE:1) Wo = (k 1 Watt Meter Reading.) Where, k 1 = Full Scale Deflection (Vsel Isel Cos ) W sc = (k 2 Watt Meter Reading.) Where, k 2 = Full Scale Deflection EQUIVALENT CIRCUIT:

20 CALCULATION: 1. FROM OPEN CIRCUIT TEST: W O = Iron Loss of Transformer I 2 = KI 2 i.e.,w O = V o I o CosФ o V 2 = V 2 / K W Therefore CosØ 0 = V0 I0 0 (Exciting Circuit Components): Magnetizing Component of Current; I m = I o SinФ o Working Component of Current; I w = I o CosФ o Exciting Resistance; R 0 = Exciting Reactance; X 0 = V I 0 w V I 0 m Ω Ω 2. FROM SHORT CIRCUIT TEST: W SC = Full Load Copper Loss of the Transformer Equivalent Resistance Referred to Primary side: W R = 2 I SC SC Ω Equivalent Impedance Referred to Primary side: Z = V I SC SC Ω Equivalent Reactance Referred to Primary side: Z Ω 2 2 X = R MODEL GRAPH: Dept. of EEE, CIT-Gubbi, Page No.10

21

22 Efficiency of the Transformer: %ŋ = S X Cos (S X Cos 1000 ) (W0 x W SC ) O/P 100 [ie ŋ %= O/P TotalLosses ] Where: S-Rating of the transformer in KVA. X- Loads (1, ¾, ½, ¼) Sl. No. Load (X) pf %ŋ 1. ¼ 2. ½ 3. ¾ ¼ 2. ½ 3. ¾ Regulation of the Transformer: % Voltage Regulation = IR CosØ IX V 0 SinØ 100 Where: I- Rated current of the transformer. + For lagging power factor & - For leading power factor. Sl. No. Pf 1. Unity %Regulation Lagging Leading Calculation.. Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.12

23 CIRCUIT DIAGRAM: Tabular Column Sl. No V max (V) V min (V) I max (A) I min (A) X d (Ω) X q (Ω) %Regulation 0.8 lag 0.8 lead Vector Diagram

24 Experiment No. 03 SLIP TEST ON ALTERNATOR Date: / / Aim To determine X d and X q of a salient pole alternator by conducting slip test and to Predetermine its regulation. Apparatus Required Procedure Sl.No Particulars Range Type Quantity Voltmeters 0 60 V MI 0 30V MC 02 Ammeters 0-1/2A MC 0-2A MI 03 Rheostats 0-750Ω,1.2 A Ω,8.5A 04 3 phase Auto-transformer Tachometer Connections are made as shown in the circuit diagram (3.a) 2. Keeping the rheostat R 1 in the field circuit of motor in cut-out position, the rheostat R 2 in the armature circuit of motor in cut-in positions, the switch S 2 in open position And 3-phase auto-transformer at zero output position, supply switch (S 1 ) is closed. 3. The motor is brought to a speed slightly less than the synchronous speed of Alternator by gradually cutting out the rheostat R 2 and cutting in the rheostat R 1, if Necessary. 4. A low voltage (say V) is applied across the rotor terminals of the alternator by varying the three phase auto transformer. 5. The following readings are noted down. Maximum value of voltage V max, Volt Minimum value of voltage v min, Volt Maximum value of current I max, Ampere Minimum value of current i min, Ampere 7. Step 5 is repeated for different values of applied voltage. 8. The three phase auto transformer is brought to its zero output position, all the rheostats are brought back to their respective initial positions and the supply switch (S 1 ) is opened. Dept. of EEE, CIT-Gubbi, Page No.14

25 Determination of Stator Resistance of Alternator (R a ) Sl. No V (Volts) I (Ampere) Resistance R DC = V/I Ω Resistance R AC =1.5 R DC

26 Determination of Stator Resistance (R a ) a. Connections are made as shown in the circuit diagram (3.b). b. By keeping rheostat in cut-in position the supply switch (S 1 ) is closed. Rheostat is adjusted to any value of current (say 1A) c. All the meter readings are noted down. d. The supply switch (S 1 ) is opened. NOTE: Field of the alternator is kept opened. Calculation V =Rated phase Voltage, Volt I = Rated current, Ampere. X d = V max / I min = Ω X q = V min / I max = Ω For 0.8 p.f lagging CosФ = 0.8 SinФ = 0.6 Therefore Ф = tanθ = ( V Sin Ф ± I X q ) / (V Cos Ф + I R a ) ( Note: + lag, - lead) θ = tan -1 ((V Sin Ф ± I X q ) / (V Cos Ф + I R a )) Therefore α =θ - Ф Therefore E o /phase = (V Cos α ± I d.x d + I q R a ) Volt Therefore Where I q = I Cos θ I d = I Sin θ Eo V V * Regulation %R= 100 Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.16

27 CIRCUIT DIAGRAM: TABULAR COLUMN: 1. BALANCED LOAD CONDITION Sl. No. A 1 (Amps) A 2 (Amps) A 3 (Amps) A 4 (Amps) A 5 (Amps) V (Volts) I 1(TEASER) (Amps) I 1(MAIN) (Amps) 2. UNBALANCED LOAD CONDITION Sl. No. A 1 (Amps) A 2 (Amps) A 3 (Amps) A 4 (Amps) A 5 (Amps) V (Volts) I 1(TEASER) (Amps) I 1(MAIN) (Amps)

28 Experiment No. 04 Date: / / SCOTT CONNECTION AIM: To verify the currents in the main Transformer and teaser transformer in Scott connection with balanced and unbalanced load. APPARATUS REQUIRED: Sl. No Particulars. Range Type Quantity. Voltmeter 0-600V MI 02. Ammeter 0-10A MI 05 PROCEDURE: 1. Connections are made as shown in the circuit diagram (4). 2. By keeping the 3-Ф auto transformer voltage in zero out-put and resistive loads in off position, the supply switch (S 1 ) is closed. 3. By varying the 3-Ф auto transformer, apply the rated voltage of the transformer (1- Ф). [say 230V] 4. Close the load switch and apply load in steps till the rated current of the transformer. At each step all the meter readings are noted down. 5. The resistive loads are brought back to the off position and 3-Ф auto-transformer to its initial zero out-put position, the supply switch (S 1 ) is opened. Calculation: I 1T = 1.15 K I 2T Amps I 1M = K I 2M Amps where; K = transformation ration of transformer I 2T = Secondary teaser transformer current I 2M = Secondary main transformer current I 1T = Primary teaser transformer current I 1M = Primary main transformer current. Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.18

29 CIRCUIT DIAGRAM:

30 Experiment No. 05 Date: / / SEPARATION OF HYSTERESIS AND EDDY CURRENT LOSSES IN SINGLE PHASE TRANSFORMER. AIM: transformer. To separation the Eddy current loss and Hysteresis loss from the iron loss of 1-Φ APPARATUS REQUIRED: PROCEDURE: Sl. No Particulars. Range Type Quantity. Voltmeter 0-300V MI 02. Ammeter 0-10A MI Ammeter 0-2A MC Rheostats 0-400Ω,1.7A 0-150Ω,2A Tachometer - Digital 05. Wattmeter 10A,600V LPF 1. Connections are made as shown in the circuit diagram (5). 2. The prime mover is started with the help of 3-point starter and it is made to run at rated speed. 3. By varying alternators field rheostat gradually, the rated primary voltage is applied to transformer. 4. By adjusting the speed of prime mover the required frequency, is obtained and corresponding reading are noted. 5. The experiment is repeated for different frequency and corresponding readings are tabulated. 6. The prime mover is switched off using the DPIC switch after bringing all the rheostats to initial position 7. From the tabulated readings the iron loss is separated from eddy current loss and hysteresis loss by using respective formulae. Dept. of EEE, CIT-Gubbi, Page No.20

31 TABULAR COLUMN Sl. No. Speed of Prime Mover (N) rpm Supply Frequency (f) Hz Primary Voltage (V) Volts Wattmeter Reading (W i ) Watts W i / f MODEL GRAPH Calculation: 1. Frequency(f)=PN s /120 Where P-number of poles; Ns-Synchronous speed in rpm 2. Hysteresis loss(w h )=A f 3. Eddy current loss(w e )=B f 2 4. Iron loss or core loss(w i )= W e +W h

32 Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.22

33 CIRCUIT DIAGRAM: Resistive Load

34 EXPERIMENT NO. 06 Date: / / NO-LOAD AND LOAD CHARACTERISTICS OF A DC-SHUNT GENERATOR Aim: To draw the external and internal characteristics of the given D.C shunt generator. Apparatus Required: Sl. No. Particulars Range Type Quantity Voltmeters 02 Ammeters 03 Rheostats 0-300V 0-30V 0-10/20 A 0-1/2A 0-750Ω,1.2A 0-38Ω, 8.5A MC MC MC MC Tachometer - - Procedure A. NO- LOAD CHARACTERISTICS 1. Connections are made as shown in the circuit diagram (6.a). 2. Keeping the rheostat R 1 in the field circuit of the motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in the field circuit of the generator in cut-in positions, and all load switches in off condition, the supply switch (S 1 ) is closed, the motors starts rotating. 3. The motor is brought to its rated speed by gradually cutting out rheostat R 2 completelyand cutting in the rheostat R 1, if necessary. 4. The generator voltage is built in steps up to its rated value by gradually cuttingout rheostat R Note down the corresponding generated voltage and field currents in steps. Plot the graph. B. LOAD CHARACTERISTICS 1. Connections are made as shown in the circuit diagram (6.a). 2. Keeping the rheostat R 1 in the field circuit of the motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in the field circuit of the generator in cut-in positions, and all load switches in off condition, the supply switch (S 1 ) is closed, the motors starts rotating. 3. The motor is brought to its rated speed by gradually cutting out rheostat R 2 completely and cutting in the rheostat R 1, if necessary. 4. The generator voltage is built up to its rated value by gradually cutting-out rheostat R 3. Dept. of EEE, CIT-Gubbi, Page No.24

35 Circuit Diagram (6.b) Determination of Armature Resistance (Ra) Resistance (Rsh) Circuit Diagram (6.c) Determination of Shunt Field Model Graph

36 5. The generator is loaded in steps by gradually applying the loads, speed of the motor is brought to its rated value by cutting in R 1 and at each step the corresponding values of the terminal voltage (V L ), the load current (I L ) and the field current (I f ) are noted. Note: (Motor or Generator should not be loaded beyond its rated value) 6. The load on the generator is completely removed; all the rheostats are brought back to their respective initial positions, then the supply switch (S 1 ) is opened. Determination of Armature Resistance (R a ) by V- I method. a. Connections are made as shown in the circuit diagram (6.b) b. Keeping the rheostat in cut-in position, the supply switch (S 1 ) is closed, Rheostat is adjusted to any value of current (say 1 A) and the readings of ammeter and voltmeter are noted down. c. The supply switch (S 1 ) is opened. Determination of Shunt field Resistance (R sh ) by V- I method. a. Connections are made as shown in the circuit diagram (6.C) b. Keeping the rheostat in cut-in position, the supply switch (S 1 ) is closed, Rheostat is adjusted to any value of current (say 0.4A) and the readings of ammeter and voltmeter are noted down. c. The supply switch (S 1 ) is opened. Characteristics Curves a. External Characteristics A graph of V L v/s I L is drawn, which represents the External Characteristics curve b. Internal Characteristics I. Graphical method 1. To Draw Q: Consider any reading Ia vs IaRa, Draw a Straight line from origin 2. To Draw P: Consider any reading If vs VL. Draw a Straight line from origin 3. Shunt field resistance line OP and armature line OQ are drawn as shown in the External characteristics curve. 4. A point F is selected on the external characteristics curve. 5. From point F, horizontal line FA and vertical line FC are drawn which are intersecting Y and X axes respectively. 6. A point D on X-axis is selected so that CD=AB, representing the shunt field current. 7. From point D a vertical line DE is drawn and it is produced to intersect to the Produced line AF at point H. 8. Point G is selected on the produced line DH so that HG=DE, which represents the armature drop. G is a point on the internal characteristics. 9. Terminal Voltage : V = OA= DH(corresponding to I a ) Dept. of EEE, CIT-Gubbi, Page No.26

37 TABULAR COLUMN 1. NO-LOAD CHARACTERISTICS Sl. No. E O (Volt) I f (Ampere) 2. LOAD CHARACTERISTICS Sl. No V L (Volt) I L (Ampere) I f (Ampere) I a = I L +I f (Ampere) E g =V+I a R a (Volts) Speed (rpm) Determination of Armature Resistance (R a ) Sl. No V (Volts) I (Ampere) Resistance R a = V/I Ω Determination of Shunt Resistance (R sh ) Sl. No V (Volts) I (Ampere) Resistance R sh = V/I Ω Dept. of EEE, CIT-Gubbi, Page No.27

38 10. Armature Voltage Drop : I a R a = DE 11. Therefore EMF generated after allowing for the drop due to armature reaction: E g = V + I a R a volt = DH+DE =DH+HG (where HG=DE) =DG GK is the drop due to armature reaction 12. Similarly some more points are located on the external characteristics curve and corresponding points on internal characteristics are determined. 13. A curve is drawn passing through these points, which represents Internal characteristics Curve. II. Analytical Method Armature Current: I a = I L + I sh Amps EMF Generated : E g =V + I a R a Volts A graph of E g v/s I a is drawn, which represents Internal characteristics. Calculation: Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.28

39 CIRCUIT DIAGRAM: TABULAR COLUMN: Sl. No V (Volts) V 1 (Volts) Sl. No V (Volts) V 1 (Volts)

40 Experiment No. 07 Date: / / POLARITY TEST ON 1-Ф TRANSFORMER AIM: To verify the voltage across the windings of a given 1-Ф Transformer for additive and subtractive connections. APPARATUS REQUIRED: Sl. No Particulars Range Type Quantity. Voltmeter 0-300V 0-600V MI MI PROCEDURE: 1. Connections are made as shown in the circuit diagram (7.a). 2. The supply switch (S 1 ) is closed. 3. The voltmeter readings are noted. 4. The supply switch (S 1 ) is opened. 5. The same procedure is repeated for circuit diagram (7.b). 6. Observe voltmeter (V 1 ) readings in both the cases. Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.30

41 CIRCUIT DIAGRAM:

42 Experiment No. 08 Date: / / POLARITY TEST AND CONNECTION OF 3 SINGLE-PHASE TRANSFORMERS IN STAR DELTA, DELTA-DELTA AND V-V (OPEN DELTA) AND DETERMINATION OF EFFICIENCY AND REGULATION UNDER BALANCED RESISTIVE LOAD. AIM: To verifyandcompare the performance of 3 single-phase transformers in delta delta and V V (open-delta) connection under load. APPARATUS REQUIRED: Sl. No Particulars Range Type Quantity Voltmeter Ammeter Wattmeter 0-300V 0-600V 10/20A 10/20A,500V MI MI MI UPF PROCEDURE A) Polarity test: 1. Connections are made as shown in the circuit diagram (8.a). 2. Close the 3-phase supply switch and apply a low voltage. 3. Check the voltage between A1 and C2 which are open. 4. For correct delta connection voltmeter must show zero or negligible reading. B) Star delta connection: 1. Connections are made as shown in the circuit diagram (8.b). 2. By keeping 3-phase auto-transformer voltage in zero position and the 3-phase resistive load in minimum position, the 3-phase supply switch is closed. 3. By varying the 3-phase auto-transformer apply the rated voltage of the transformer (400V). 4. By keeping the 3-phase resistive load in minimum position note down the no-load voltage. 5. Apply the load in steps up to the rated current of the transformer. At each step all the meter readings are noted down. 6. The resistive loads are brought back to its initial minimum position and 3-Ø autotransformer to its initial zero out-put position, the supply switch is opened. Dept. of EEE, CIT-Gubbi, Page No.32

43

44 C) Delta Delta connection. 1. Connections are made as shown in the circuit diagram (8.b). 2. By keeping 3-phase auto-transformer voltage in zero position and the 3-phase resistive load in minimum position, the 3-phase supply switch is closed. 3. By varying the 3-phase auto-transformer apply the rated voltage of the transformer (230V). 4. By keeping the 3-phase resistive load in minimum position note down the noload voltage. 5. Apply the load in steps up to the rated current of the transformer. At each step all the meter readings are noted down. 6. The resistive loads are brought back to its initial minimum position and 3-Ø auto-transformer to its initial zero out-put position, the supply switch is opened. C) Open delta (V-V) connection. 1. Connections are made as shown in the circuit diagram (8.c). 2. By keeping 3-phase auto-transformer voltage in zero position and the 3-phase resistive load in minimum position, the 3-phase supply switch is closed. 3. By varying the 3-phase auto-transformer apply the rated voltage of the transformer (230V). 4. By keeping the 3-phase resistive load in minimum position note down the noload voltage. 5. Apply the load in steps up to the rated current of the transformer. At each step all the meter readings are noted down. 6. The resistive loads are brought back to its initial minimum position and 3-Ø auto-transformer to its initial zero out-put position, the supply switch is opened. Dept. of EEE, CIT-Gubbi, Page No.34

45 TABULAR COLUMN: Sl.No V (Volts) V 1 (Volts) A. FOR STAR DELTA CONNECTION Sl.No V 1 (Volts) I 1 (Amps) I 2 (Amps) I 3 (Amps) I 4 (Amps) W 1 (Watt) W 2 (Watt) W 3 (Watt) W 4 (Watt) V 2 (Volts) B. FOR DELTA DELTA CONNECTION Sl.No V 1 (Volts) I 1 (Amps) I 2 (Amps) I 3 (Amps) I 4 (Amps) W 1 (Watt) W 2 (Watt) W 3 (Watt) W 4 (Watt) V 2 (Volts) C. FOR OPEN DELTA (V-V) CONNECTION Sl.No V 1 (Volts) I 1 (Amps) I 2 (Amps) I 3 (Amps) I 4 (Amps) W 1 (Watt) W 2 (Watt) W 3 (Watt) W 4 (Watt) V 2 (Volts) Dept. of EEE, CIT-Gubbi, Page No.35

46 Calculation: (Vsel Isel Cos ) NOTE: 1)W 1 = (k 1 Watt Meter Reading.) Where, k 1 = Full Scale Deflection (Vsel Isel Cos ) W 2 = (k 1 Watt Meter Reading.) Where, k 2 = Full Scale Deflection (Vsel Isel Cos ) W 3 = (k 3 Watt Meter Reading.) Where, k 3 = Full Scale Deflection (Vsel Isel Cos ) W 4 = (k 4 Watt Meter Reading.) Where, k 4 = Full Scale Deflection % ŋ = W 3 + W 4 W 1 + W %Voltage regulation = V 2 no load V 2 full load V 2 full load Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.36

47 CIRCUIT DIAGRAM:

48 Experiment No. 09 Date: / / SUMPNER S TEST AIM: To conduct the Sumpner s test, or Back to Back test on two identical transformers to predetermine their efficiency. APPARATUS REQUIRED: Sl. No Particulars Range Type Quantity. Voltmeter 02. Ammeter 03 Wattmeter NOTE: Use 2 similar rating transformers. PROCEDURE: 0-300V 0-600V 0-2A 0-10/20A MI MI MI MI 2A,300V LPF 10/20A,75V UPF 1. Connections are made as shown in the circuit diagram (9). 2. By keeping the 1-Ф auto-transformers (1) and (2) in zero out-put positions, SPST switch (S 3 ) and DPST switch (S 2 ) in open positions, the supply switch (S 1 ) is closed. 3. Vary the 1-Ф auto-transformer no-(1) gradually and apply the rated voltage of the transformer. [say 230V] 4. The reading of voltmeter (V 2 ) connected across the SPST switch (S 3 ) is observed. It should read zero; if not, the auto-transformer is brought back to its initial zero out-put position, open the supply switch (S 1 ) and interchange one of the transformer s secondary terminals. 5. Close the supply switch (S 1 ), repeat step no-3. Close SPST switch (S 3 ). (By ensuring voltmeter (V 2 ) reads zero). The watt-meter (W 0 ), voltmeter (V 1 ) and ammeter (I 1 ) readings are noted down. 6. Switch (S 2 ) is closed and by operating the auto-transformer (2) very slowly, a low voltage is applied such that rated current flows through the transformer. The wattmeter (W CU ) and ammeter (I 2 ) readings are noted down. 7. The auto-transformers (2) and then (1) are brought back to their initial zero output positions, the DPST switch (S 2 ), SPST switch (S 3 ), and supply switch (S 1 ) are opened. Dept. of EEE, CIT-Gubbi, Page No.38

49 TABULAR COLUMN: Sl. No V 1 (Volts) I 1 (Amps) W o (Watt) I 2 (Amps) W cu (Watt) NOTE:1) W o = (k 1 Watt Meter Reading.) Where, k 1 = W cu = (k 2 Watt Meter Reading.) Where, k 2 = (Vsel Isel Cos ) FullScaleDeflection (Vsel Isel Cos ) FullScaleDeflection MODEL GRAPH: Calculation Rated current of Transformer = kva x 1000 Rated Voltage Total Iron loss in both transformers = W i = Watt Iron loss in each transformer = W i/2 = 2 W i = Watt Full load total Copper loss of both transformers = W cu = Watt

50 Full load Copper loss of each transformer = W CU/2 = 2 W cu = Watt a. For combined efficiency (ŋ) S X cos 1000 %ŋ= S X cos 1000 Wi x W cu [ie ŋ %= O/P O/P TotalLosses ] NOTE:S = Rating of the transformer in KVA (i.e., 2 KVA is used here) {S = 4:-for combined efficiency of transformers. S = 2:-for efficiency of each transformer.} b. For individual efficiency (ŋ) S X cos 1000 %ŋ= 100 [i.e., ŋ%= 2 S X cos 1000 Wi/2 x W cu/2 O/P O/P TotalLosses ] Combined efficiency (ŋ) Individual efficiency (ŋ) Sl. No x (Load) pf % ŋ ¾ UPF 03. ½ 04. ¼ ¾ ½ 08. ¼ Sl. No x (Load) pf % ŋ ¾ 03. ½ UPF 04. ¼ ¾ ½ 08. ¼ Signature of Staff-incharge Dept. of EEE, CIT-Gubbi, Page No.40

51 CIRCUIT DIAGRAM:

52 Experiment No. 10 Date: / / SYNCHRONIZATION OF ALTERNATOR TO INFINITE BUS AND DETERMINATION OF PERFORMANCE UNDER CONSTANT POWER AND VARIABLE EXCITATION & VICE-VERSA. Aim To operate the Alternator on Infinite Bus. Constant Power and Variable Excitation. Variable Excitation and Constant Power. Apparatus Required Procedure Sl. No. Particulars Range Type Quantity Voltmeter V MI 02 Ammeters 0-1/2A MC 0-5/10A MI 03 Rheostats 0-750Ω,1.2A Ω,8.5A - 04 Watt meters 10/20A, V LPF Tachometer - - a. Operation on Infinite Bus Bar 1. Connections are made as shown in the circuit diagram (10.a) 2. Keeping the rheostat R 1 in the field circuit of motor in cut-out position, the rheostat R 2 in the armature circuit of motor and the rheostat R 3 in the field circuit of alternator in cut-in positions, the bus bar switch (S 2 )and synchronizing switch (S 3 ) in open positions, the supply switch (S 1 ) is closed. 3. The motor is brought to the synchronous speed of the alternator by gradually cutting out the rheostat R 2 and cutting in the rheostat R 1, if necessary. By gradually cutting out the rheostat R 3, the alternator voltage is built-up to the bus bar voltage. 4. Now, bus bar switch (S 2 )is closed, and the phase sequence is verified. For correct phase sequence, all the lamps will flicker simultaneously. Otherwise, they flicker alternately. If they flicker alternatively, the bus bar voltage switch is opened and any two terminals of the bus bar supply are interchanged. 5. Repeat step number 2, 3 and By varying the rheostats R 1, R 2 and R 3 the dark period of the lamps are obtained. 7. When all the lamps are in dark condition, the synchronization switch S 3 is closed and now the alternator is connected in parallel with the bus bar. 8. Switches (S 3 ) and (S 2) are opened; all the rheostats are brought back to their respective initial positions, and supply switch (S 1 ) is opened. Dept. of EEE, C.I.T, Gubbi, Page No.42

53

54 b. Constant Power - Variable Excitation Operation 1. Connections are made as shown in the circuit diagram (10.b) 2. Follow the procedure steps 2, 3 of procedure (a) 3. By gradually cutting out the rheostat R 3, the alternator voltage is built-up to its rated voltage. 4. Apply load gradually. 5. Vary generator excitation (R3) to keep wattmeter readings constant (Total Power). 6. Tabulate the readings. 7. Bring back the load to zero, reduce the excitation to a normal value and all rheostats are brought back to respective initial positions & supply switch (S 1 )is opened. c. Constant Excitation - Variable Power Operation 1. Connections are made as shown in the circuit diagram (10.b) 2. Follow the procedure steps 2, 3 of procedure (a). 3. By gradually cutting out the rheostat R 3, the alternator voltage is built-up to its rated voltage. 4. Apply load in steps & note down all meter readings (Excitation should be constant by adjusting the speed of the Motor). 5. Bring back the load to zero, reduce the excitation to a normal value and all rheostats are brought back to respective initial positions & supply switch (S 1 ) is opened. Dept. of EEE, C.I.T, Gubbi, Page No.44

55 Tabular Column 1. Constant Power - Variable Excitation Operation Sl. No. I f (A) Power (W1+W2) Speed (RPM) Voltage (V) I L (A) 2. Constant Excitation - Variable Power Operation Sl. No. I f (A) Power (W1+W2) Speed (RPM) Voltage (V) I L (A) Dept. of EEE, C.I.T, Gubbi, Page No.45

56 Calculation: Signature of Staff-incharge Dept. of EEE, C.I.T, Gubbi, Page No.46

57 CIRCUIT DIAGRAM:

58 Experiment No. 11 Date: / / REGULATION OF ALTERNATOR BY EMF AND MMF METHOD Aim To determine the percentage regulation of the given three phase alternator by Open circuit and short circuit tests. By EMF method By MMF method Apparatus Required Sl.No Particulars Range Type Quantity Voltmeters 02 Ammeters 0-30V 0-500V 0-10/20A 0-1/2A MC MI MI MC 03 Rheostats 0-750Ω,1.2A 0-38Ω,8.5A Tachometer - - Procedure a. Open Circuit Test 1. Connections are made as shown in the circuit diagram (11.a) 2. Keeping the rheostat R 1 in the field circuit of motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in field circuit of the alternator in cut-in positions and TPST (S 2 ) in open position, the supply switch (S 1 ) is closed. 3. The motor is brought to synchronous speed by cutting out the rheostat R 2 and then by cutting in the rheostat R 1, if necessary. 4. By gradually cutting out the rheostat R 3, the readings of ammeter (A 1, 0-2A) and voltmeter (V) are noted down. 5. The above step is continued until voltmeter reads about 1.25 times the rated voltage of the alternator. b. Short Circuit Test 1. The rheostat R 3 is brought to its initial position (cut-in) and TPST (S 2 ) is closed. 2. By gradually cutting out the rheostat R 3, reading of the ammeter (A 2, 0-10/20A) is adjusted to the rated current of the alternator and the corresponding field current (A 1 ) is noted down. 3. All the rheostats are brought back to their respective initial positions, TPST switch (S 2 ) and supply switch (S 1 ) are opened. Dept. of EEE, C.I.T, Gubbi, Page No.48

59 Tabular Column 1. Open Circuit Test 2. Short Circuit Test Sl.No I f Amps VL V 0 Volts Vph Sl.No I f Amps I sc Amps

60 Determination of Armature Resistance (R a ) by V-I Method 1. Connections are made as shown in the circuit diagram (11.b) 2. Keeping the rheostat in cut-in position, the supply switch (S 1 ) is closed, Rheostat is adjusted to any value of current (say 1A) and the readings of ammeter and voltmeter are noted down. 3. The supply switch (S 1 ) is opened. Calculation I. EMF Method i. Draw OCC and SCC for suitable scales as shown in model graph no (1). ii. Mark a point A on the OCC corresponding to the rated voltage and draw a Perpendicular so that it cuts SCC line at a point B and X-axis at point C. iii. Corresponding to point A, E 1 is the open circuit voltage per phase, and BC is the Short circuit current. Therefore Synchronous impedance per phase Zs = E 1 /I 1 Ω (I f Constant) Synchronous reactance per phase X s = Z s 2 - R a 2 Ω iv. Determination of % Regulation: V = Rated voltage per phase, Volt. I = Rated Current, Ampere. Ф = Phase angle (a) Regulation for lagging power factor: From the vector diagram, as shown in fig.(2) OB = OA 2 + AB 2 i.e. E = ((V cosф+ IR a ) 2 + (V sinф + IX s ) 2) Volt. E V V * Therefore %R= 100 (b) Regulation for leading power factor: From the vector diagram, as shown in fig.(3) OB = OA 2 + AB 2 i.e. E = ((V cosф+ IR a ) 2 + (V sinф - IX s ) 2 )Volt. E V V * Therefore %R= 100. (c) Regulation for Unity power factor: From the vector diagram, as shown in fig.(1) E = ((V + IR a ) 2 + IX s 2 )Volt. E V V * Therefore %R= 100 Dept. of EEE, C.I.T, Gubbi, Page No.50

61 Determination of Stator Resistance of Alternator (R a ) Sl.No V (Volts) I (Ampere) Resistance R DC = V/I Ω Resistance R AC =1.5*R DC % Regulation Tabular Column PF REMARKS LEAD LAG LEAD LAG FOR E.M.F METHOD FOR M.M.F METHOD Dept. of EEE, C.I.T, Gubbi, Page No.51

62 II. MMF Method i. Draw the OCC and SCC for suitable scales as shown in model graph no. (2) ii. Mark the point F on the OCC corresponding to the rated voltage. iii. Draw a perpendicular and let it cuts X-axis at point A. iv. Mark the point G on SCC corresponding to the rated current, I sc, now, OA = Field current required to produce rated voltage under open circuit condition and OC = Field current required to produce full load current under short circuit condition. f. Regulation for lagging power factor: model graph no. (2) At point A, take the vector at an angle = (90+Ф); Where Ф is the lagging power factor angle and take AB = OC. Therefore OB = Total field current (Vector sum) in Ampere. (with O as center and radius equal to OB, an arc is drawn cutting X-axis at point D. projection of D on OCC gives the no-load voltage E t ) E V V * Therefore %R= 100 b. Regulation for leading power factor: model graph no. (3) At point A, take the vector at an angle = (90-Ф); Where Ф is the leading power factor angle and take AB = OC. (Same procedure is followed to determine the Regulation.) Dept. of EEE, C.I.T, Gubbi, Page No.52

63 Model Graphs 1. EMF Method Graph No MMF Method Graph No. 2 Graph No. 3

64 Vector Diagrams I. EMF METHOD 1. UNITY POWER FACTOR 2. LAGGING POWER FACTOR 3. LEADING POWER FACTOR II. MMF METHOD Regulation Curve CALCULATION: Signature of Staff-incharge

65 CIRCUIT DIAGRAM:

66 Experiment No. 12 Date: / / PARALLEL OPERATION OF TWO 1-Ф TRANSFORMERS AIM: To operate two 1-Ф transformers in parallel and verify how a common load is shared between them. APPARATUS REQUIRED: Sl. No Particulars. Range Type Quantity. Voltmeter 0-500V MI 0-30V MI 02. Ammeter 0-5 MI 0-20A MI Wattmeter 20A,300V UPF 10/20A,75V UPF 5A,300V UPF PROCEDURE: 1) PARELLEL OPERATION 1. Circuit connections are made as shown in the circuit diagram (12.a). 2. Keeping the load switch (S 2 ) and SPST switch (S 3 ) in open position, the supply switch (S 1 ) is closed. 3. By varying the 1-Ф auto transformer the rated voltage of the transformers is applied. [Say 230V]. 4. The reading of the voltmeter connected across SPST switch (S 3 ) is observed. It should read zero; if not, (if shows double the supply voltage) the auto transformer is brought back to its zero output position then the supply switch (S 1 ) is opened. 5. The secondary connections of any one of the transformers is interchanged and close the supply switch (S 1 ). 6. Now close the SPST switch (S 3 ). (Ensuring voltmeter V 2 reads zero voltage) 7. The load switch (S 2 ) is Closed. Gradually the load is applied in steps. At each step all the meter readings are noted down. The load is applied until the full load current of both the transformers reached. 8. Gradually the load is removed, the SPST switch (S 3 ) and load switch (S 2 ) are opened. 9. Gradually reduce the auto transformer voltage to zero then supply switch (s 1 ) is opened. Dept. of EEE, C.I.T, Gubbi, Page No.56

67 TABULAR COLUMN: 1. PARELLEL OPERATION Sl. No W 1 (Watt) W 2 (Watt) W 3 (Watt) I 1 (Amps) I 2 (Amps) I 3 (Amps) Actual Theoretical Actual Theoretical 2. SHORT CIRCUIT TEST Transformer I sc W sc V sc Remarks 1. 2 KVA 2. 1 KVA NOTE: 1)W 1 = (k 1 Watt Meter Reading.) Where, k 1 = W 2 = (k 1 Watt Meter Reading.) Where, k 2 = W 3 = (k 3 Watt Meter Reading.) Where, k 3 = W sc = (k 4 Watt Meter Reading.) Where, k sc = (Vsel Isel Cos ) FullScaleDeflection I Cos ) (Vsel sel FullScaleDeflection I Cos ) (Vsel sel FullScaleDeflection (Vsel Isel Cos ) FullScaleDeflection

68 2) SHORT CIRCUIT TEST 1. Connections are made as shown in the circuit diagram (12.b). 2. Keeping 1-Ф auto-transformer voltage in zero out-put position, the supply switch (S 1 ) is closed. 3. By varying the 1-Ф auto transformer voltage very slowly, a low voltage is applied such that rated current flows through the transformer. 4. The readings of all the meters are noted down. 5. The auto-transformer is brought back to its initial zero output position, the supply switch (S 1 ) is opened. 6. The above steps are repeated for another transformer. CALCULATION: 1. For Transformer I (4 KVA) Z = VSC SC Ω = R = 2 ISC ISC W Ω = X = Z Ω= R1 2. For Transformer II (1 KVA) Z 02 = VSC SC Ω = R02 = 2 ISC ISC W Ω = X02 = Z Ω= R2 THEORETICAL CALCULATION: I 1 = Z I 3 Z 02 Z 02 = 2 R R X X 2 I 3 02 R 2 02 X Amps I 2 = Z I 3 Z Z 02 = 2 R R X X 2 I 3 02 R 2 X 2 02 Amps Calculation.. Signature of Staff-incharge Dept. of EEE, C.I.T, Gubbi, Page No.58

69 CIRCUIT DIAGRAM: Tabular Column 1. Open Circuit Test 2. Short Circuit Test Sl.No I f Amps VL V 0 Volts Vph Sl. No I f Amps I sc Amps

70 Experiment No. 13 Date: / / Aim POWER ANGLE CURVE OF SYNCHRONOUS GENERATOR To study the power angle curve of Synchronous Generator. Apparatus Required Sl.No Particulars Range Type Quantity Voltmeters 02 Ammeters 0-30V 0-500V 0-10/20A 0-1/2A MC MI MI MC 03 Rheostats 0-750Ω,1.2A 0-38Ω,8.5A Tachometer - - Procedure a. Open Circuit Test 1. Connections are made as shown in the circuit diagram (13.a) 2. Keeping the rheostat R 1 in the field circuit of motor in cut-out position, the rheostat R 2 in the armature circuit of the motor and the rheostat R 3 in field circuit of the alternator in cut-in positions and TPST (S 2 ) in open position, the supply switch (S 1 ) is closed. 3. The motor is brought to synchronous speed by cutting out the rheostat R 2 and then by cutting in the rheostat R 1, if necessary. 4. By gradually cutting out the rheostat R 3, the readings of ammeter (A 1, 0-2A) and voltmeter (V) are noted down. 5. The above step is continued until voltmeter reads about 1.25 times the rated voltage of the alternator. b. Short Circuit Test 6. The rheostat R 3 is brought to its initial position (cut-in) and TPST (S 2 ) is closed. 7. By gradually cutting out the rheostat R 3, reading of the ammeter (A 2, 0-10/20A) is adjusted to the rated current of the alternator and the corresponding field current (A 1 ) is noted down. 8. All the rheostats are brought back to their respective initial positions, TPST switch (S 2 ) and supply switch (S 1 ) are opened. Dept. of EEE, C.I.T, Gubbi, Page No.60

71 Determination of Stator Resistance of Alternator (R a ) Sl.No V (Volts) I (Ampere) Resistance R DC = V/I Ω Resistance R AC =1.5*R DC

72 Determination of Armature Resistance (R a ) by V-I Method 9. Connections are made as shown in the circuit diagram (13.b) 10. Keeping the rheostat in cut-in position, the supply switch (S 1 ) is closed, Rheostat is adjusted to any value of current (say 1A) and the readings of ammeter and voltmeter are noted down. 11. The supply switch (S 1 ) is opened. Power angle curve 1. Connections are made as shown in the circuit diagram (13.c) 2. Follow the procedure steps 2, 3 of procedure (a). 3. By gradually cutting out the rheostat R 3, the alternator voltage is built-up to its rated voltage. 4. Apply load in steps & note down all meter readings (Excitation should be constant by adjusting the speed of the Motor). 5. Bring back the load to zero, reduce the excitation to a normal value and all Calculation rheostats are brought back to respective initial positions & supply switch (S 1 ) is opened. I. EMF Method i. Draw OCC and SCC for suitable scales as shown in model graph no (1). ii. Mark a point A on the OCC corresponding to the rated voltage and draw a Perpendicular so that it cuts SCC line at a point B and X-axis at point C. iii. Corresponding to point A, E 1 is the open circuit voltage per phase, and BC is the Short circuit current. Therefore Synchronous impedance per phase Zs = E 1 /I 1 Ω (I f Constant) Synchronous reactance per phase X s = Z s 2 - R a 2 Ω Model Graph: Graph No. 1

73 Sl. No. If (Amps) Ia (Amps) W1 x K1 (Watt) W2 x K2 (Watt) N (rpm) V (Volts) E (Volts) P = W1 + W2 (Watt) δ Degree Model Graph: The maximum power occurs at δ = 90 o. Beyond this point the machine falls out of step and loses synchronism. The machine can be taken up to P i max only by gradually increasing the load. This is known as the steady state stability limit of the machine. The is normally operated at δ much less than 90 o.

74 Calculations R a = Ohm Z s = Ohm X s = Ohm P = W 1 + W 2 Watts E = V + j IZ s E = V 2 + (IZ S ) 2 Where E = Generator internal emf V = Terminal voltage δ = Load angle i. e angle between the E and V. X S = Synchronous Reactance Signature of Staff-incharge

75 QUESTION BANK 1. Pre-determine the efficiency and regulation of the given single Phase transformer at full load 0.8 p.f. lag and lead by conducting necessary tests. 2. By conducting necessary tests on a given single phase transformer, pre determine the %η at ½ full load 0.8 p.f lag and 0.8 p.f lead. 3. By conducting test on a single phase transformer, draw regulation V S p.f curve. 4. Draw the equivalent circuit of the given single phase transformer by conducting necessary tests. 5. Draw the %η V S load, curve of a given single phase transformer at 0.8 p.f lag by conducting necessary tests on it. 6. Conduct load test on a given single Phase transformer and draw its %η V S load curve. 7. Conduct load test on a given single phase transformer and determine its %η and voltage regulation at 4 amps. 8. Pre determine the combined efficiency of two similar transformers at full load, by conducting suitable experiment. 9. Conduct back to back test on a given two similar transformers, determine its %η at ½ full load 0.8 p.f lag and 0.6 p.f lead of a individual transformer. 10. Conduct Sumpner s test on a given two similar transformers, determine its combined %η at ¾ full load 0.6 p.f lag and lead. 11. Determine load sharing of two dissimilar transformers connected in parallel, when the load is 2KW. 12. Determine the primary currents of two dissimilar transformers connected in parallel when the load current is 5A. 13. Conduct an experiment on a single transformer to obtain the voltage zero and double the voltage by making necessary connections. 14. Determine the main transformer primary current and teaser transformer primary current when its secondary current is 4 Amp each by conducting necessary experiment. 15. Determine the efficiency and regulation for three single phase transformers connected in y- at full load. 16. Conduct and compare the performance of 3 single-phase transformers in delta delta and V V (open-delta) connection under load. 17. Conduct load test on a Scott connected transformer to obtain main transformer primary current and teaser transformer Primary current when the load current on main transformer is 3 Amps and the load current on teaser transformer is 4 Amps. 18. Conduct polarity test and connection of 3 single-phase transformers in star delta and determination of efficiency and regulation under balanced resistive load. 19. Conduct suitable experiment for separation of hysteresis and eddy current losses in single phase transformer. 20. Conduct suitable experiment on a given three phase Alternator and determine its regulation at full load p.f by ZPF method. Dept. of EEE, C.I.T, Gubbi, Page No.65

76 21. By conducting suitable experiment, Pre determine the regulation of the given three phase Alternator by EMF method at full load p.f (lag/lead) 22. By conducting suitable experiment, Pre determine the Regulation of the given three phase Alternator by MMF method at full load p.f (lag/lead) 23. By conducting suitable experiments on the given three phase alternator to find its Synchronous reactance. 24. By conducting suitable experiments on the given three phase alternator, find the Potier reactance. 25. By conducting suitable experiment to Pre determine the regulation of the given three phase Alternator by Potier Triangle method at full load p.f (lag/lead). 26. By conducting suitable experiment on the given salient pole alternator, predetermine the regulation at full load p.f (lag/lead). 27. Conduct a suitable experiment to measure the direct and quadrature axis reactance and predetermination of regulation of salient pole synchronous machines. 28. By conducting suitable experiment synchronize a 3phase Alternator to Infinite Bus-bar. 29. Conduct a suitable experiment to operate the given three Phase alternator on Constant power and variable excitation. 30. Conduct a suitable experiment to operate the given three phase alternator on Constant excitation and variable power. 31. Obtain the following performance characteristics of the given DC Shunt Generator by conducting suitable experiment. Determine the induced emf at load. (Graphically/ Analytically) a. Internal Characteristics 32. Obtain the following performance characteristics of the given DC Shunt Generator by conducting suitable experiment. a. External Characteristics b. Internal Characteristics and determine the induced emf at load. 33. Conduct a suitable experiment to obtain the no load and load characteristics of DC Shunt generator.!!!!!!! WISH YOU ALL THE BEST!!!!!! Dept. of EEE, C.I.T, Gubbi, Page No.66

77 VIVA VOCE QUESTIONS 1. What is the basic principle of operation of a single phase transformer? 2. What are the losses in a transformer? 3. Why the efficiency of transformer is higher than the rotating machines? 4. At full load, copper loss = 80 Watt and Iron loss =30 Watt. What will be the values of copper loss and Iron loss at half load? 5. What is regulation of a transformer? 6. For a good transformer regulation should be low or high. 7. What information you will get by conducting O.C & S.C tests? 8. What do you mean by predetermination of efficiency and regulation of a transformer? 9. What happens if the primary of the transformer is excited by a D.C source? 10. What is the condition for maximum efficiency? 11. Why Sumpner s test is also called as back to back test? 12. Why does the test needs two identical transformers? 13. What information you will get by conducting this test? 14. What is the advantage of this test? 15. What are the limitations of this test? 16. Distinguish between commercial efficiency and all day efficiency. 17. Parallel Operation of Two single Phase Transformers 18. What are conditions to be satisfied for parallel operation of single phase transformers? 19. What is the necessity of paralleling transformers? 20. How two transformers share the common load? 21. What is meant by circulating current with respect to parallel operation of transformers? 22. Separation of Losses in a Single Phase transformer 23. What are the sources of heat in a power transformer? 24. Why the transformer core is laminated? Give Reasons? 25. How does Hysteresis loss and Eddy current loss take place in a magnetic material? 26. What is polarity test? 27. What is the necessity of polarity test? Dept. of EEE, C.I.T, Gubbi, Page No.67

78 28. What is the effect of current and voltage in Star Delta Connection? 29. Where the star delta connection applicable? 30. What happens if resistive load is replaced by capacitive or inductive load? 31. How 2- phase supply can be obtained from 3- phase supply? 32. How many transformers are used in Scott connection? Name them. 33. Draw the vector diagram for Scott connection. 34. Distinguish between an Auto-transformer and a two winding transformer. 35. Write down the equation for frequency of emf induced in an Alternator. 36. Name the types of Alternator based on their rotor construction. 37. Which type of Synchronous generators are used in Hydro-electric plants and why? 38. What are the advantages of salient pole type construction used for Synchronous machines? 39. Why is the stator core of Alternator laminated? 40. What are the causes of changes in voltage in Alternators when loaded? 41. Define the term voltage regulation. 42. State the condition to be satisfied before connecting two alternators in parallel. 43. What is meant by infinite bus-bars? 44. How do the synchronizing lamps indicate the correctness of phase sequencebetween existing and incoming Alternators? 45. Why are Alternators rated in kva and not in kw? Dept. of EEE, C.I.T, Gubbi, Page No.68

79 References 1. Electric Machinery by A. E. Fitzgerald, Charles Kingsley Jr. & Stephen Umans 2. Electric Machinery and Transformers (The Oxford Series in Electrical and Computer Engineering) by Bhag S. Guru and Hüseyin R. Hiziroglu (Jul 20, 2000) 3. The performance and design of alternating current machines BY M.G.SAY, Third Edition, CBS Publishers & Distributors 4. Transformers by BHEL, Bhopal (MP) TATA MCGRAW HILL. 5. Electrical Machinery by Dr.P.S.Bimbhra, Kanna Publisher 6. Theory of Alternating Current Machinery, Alexander S. Langsdorf TATA MCGRAW HILL. 7. Electrical Technology Volume II, by B.L.THERAJA, S Chand Publication Dept. of EEE, C.I.T, Gubbi, Page No.69

80 Appendix STUDY OF ELECTRICAL SYMBOLS Sl. No. Particulars 1 Electrical wire Symbol 2 Connected wires 3 Not connected wires 4 SPST Toggle switch 5 SPDT Toggle switch 6 Pushbutton Switch (N.O) 7 Pushbutton Switch (N.C) 8 Earth Ground 9 Chassis ground 10 SPST Relay 11 SPDT Relay 12 Digital Grounding 13 Resistor 14 Potentiometer 15 Variable Resistor 16 Polarized Capacitor 17 Inductor 18 Iron-core Inductor Dept. of EEE, C.I.T, Gubbi, Page No.70

81 19 Variable Inductor 20 DC Voltage Source 21 Current Source 22 AC Current Source 23 Generator 24 Battery Cell 25 Battery 26 Controlled Voltage Source- DC 27 Controlled Current source 28 Voltmeter 29 Ammeter 30 Ohm meter 31 Wattmeter 32 Lamp/Light/Bulb 33 Motor 34 Transformer 35 Fuse 36 Electrical Bell 37 Buzzer 38 Bus 39 Loudspeaker 40 Microphone 41 Arial Antenna Dept. of EEE, C.I.T, Gubbi, Page No.71

82 42 Circuit Breaker 43 Contacts Closed NC 44 Contacts Open - NO 45 AC Generator 46 DC Generator 47 Relay with Transfer Contacts 48 Current Transformer 49 Loud Speaker 50 Heater 51 DPST 52 DPDT 53 Relay with Contacts 54 Thermistor 55 Full wave, Bridge Type Rectifier 56 Inductor Solenoid / Coil 57 DC Motor 58 AC Motor 59 Galvanometer 60 VAR Meter 61 Power-Factor Meter 62 Isolation Transformer Dept. of EEE, C.I.T, Gubbi, Page No.72

83 63 Variable Voltage Transformer 64 Auto Transformer 65 Current Transformer with Two Secondary Windings On One Core 66 Motor Operated Valve 67 Electrical Distribution Panel 68 Junction Box 69 Instrument Panel or Box 70 Lightning Arrestor 71 Lighting Rod 72 Choke 73 One-way switch 74 Two-way switch 75 Intermediate switch 76 Spot light 77 Distribution Board 78 Fan 79 Joint Box 80 Short circuit device 81 Emergency push button 82 Lighting outlet position 83 Lighting outlet on wall 84 Connector Dept. of EEE, C.I.T, Gubbi, Page No.73

84 85 Light Emitting Diode 86 Photo Cell 87 Voltage Indicator capacitive 88 General caution 89 Poisonous sign 90 Radio Activity sign 91 Ionizing radiation sign 92 Non-ionizing radiation sign 93 Biohazard sign 94 Warning sign 95 High voltage sign 96 Magnetic field symbol 97 Chemical weapon symbol 98 Laser hazard sign 99 First Aid 100 Fire Extinguisher