EE305 Electrical Machines Laboratory I - Lab Manual PDF

EE305 – Electrical Machines Laboratory – I Ramulu Ch Department of Electrical Engineering NIT Warangal INDIA NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL (An Institution of National Importance)...

EE305 – Electrical Machines Laboratory – I Ramulu Ch Department of Electrical Engineering NIT Warangal INDIA NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL (An Institution of National Importance) Telangana – 506 004. INDIA. DEPARTMENT OF ELECTRICAL ENGINEERING ELECTRICAL MACHINES LABORATORY MANUAL FOR EE305 – ELECTRICAL MACHINES LABORATORY – I III B.Tech. in Electrical and Electronics Engineering First Semester ACADEMIC YEAR: 2024-2025 (ODD SEM) Prepared by Dr. Ch. Ramulu Faculty In-charge of Electrical Machines Lab  CONTENTS LIST OF EXPERIMENTS…………………………………………………………………………………………. ii ELECTRICAL MACHINES LABORATORY SAFETY RULES…………………………………………. iii LAB INSTRUCTIONS…………………………………………………………………………………………….. GENERAL ELECTRICAL SYMBOLS…………………………………………………………………………. v 1 Determination of open circuit characteristics of DC machine………………. 1 2 Determination of Load characteristics of DC generators………………………. 4 Speed control of DC motors using armature control and field control 3 8 method……………………………………………………………………………………………………. 4 Brake test on DC Shunt motor………………………………………………………………… 11 5 Swinburne’s Test on a DC Machine…………………………………………………………. 14 6 Retardation test on DC machines to determine the Moment of Inertia.. 18 7 Field test on two identical DC series machines…………………………………….. 21 8 Hopkinson’s test on DC shunt machines…………………………………………………. 27 9 Open circuit and short circuit tests on a single phase transformer………. 30 10 Load test on a single phase transformer………………………………………………… 36 11 Sumpner’s test on a single phase transformer………………………………………. 39 12 Separation of no-load losses of a single phase transformer………………….. 42 13 Scott connection of single phase transformers………………………………………. 45 APPENDIX I DC motor starters………………………………………………………………………………………………. I Types of Resistors………………………………………………………………………………………………. II Types of Capacitors……………………………………………………………………………………………. III Types of Inductors………………………………………………………………………………………………. IV Classification of DC machines……………………………………………………………………………. V Classification of transformers……………………………………………………………………………. V  NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL (An Institution of National Importance) DEPARTMENT OF ELECTRICAL ENGINEERING B.Tech (EEE) – V Semester EE305 – ELECTRICAL MACHINES LABORATORY - I CO1 Select apparatus based on the ratings of DC Machines and transformers CO2 Determine equivalent circuit parameters and performance of transformers Evaluate the performance of DC machines and transformers by direct and CO3 indirect loading methods CO4 Select braking and speed control methods of DC machines LIST OF EXPERIMENTS # Name of the Experiment 1 Determination of open circuit characteristics of DC machine Expt-1 2 Determination of Load characteristics of DC generators 3 Speed control of DC motors using armature control and field control method Expt-2 4 Brake test on DC Shunt motor 5 Swinburne’s Test on a DC Machine Expt-3 6 Retardation test on DC machines to determine the Moment of Inertia 7 Field test on two identical DC series machines Expt-4 8 Hopkinson’s test on two DC shunt machines Expt-5 9 Open circuit and short circuit tests on a single phase transformer Expt-6 10 Load test on a single phase transformer 11 Sumpner’s test on a single phase transformer Expt-7 12 Separation of no-load losses of a single phase transformer Expt-8 13 Scott connection of single phase transformers - EED/EE305-EMLAB-1/CHR ii  NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL DEPARTMENT OF ELECTRICAL ENGINEERING ELECTRICAL MACHINES LABORATORY SAFETY RULES The following general rules and precautions are to be observed at all times in the laboratory. These rules are for the benefit of the experimenter as well as those around him/her. Additional rules and precautions may apply to a particular laboratory. 1) There must be at least two personnel in the laboratory while working on live circuits. 2) Shoes must be worn at all times. 3) Remove all loose conductive jewellery and trinkets, including rings, which may come in contact with exposed circuits. (Do not wear long loose ties, scarves, or other loose clothing around machines). 4) Consider all circuits to be "hot" unless proven otherwise. 5) Never hurry. Haste causes many accidents. 6) Always see that power is connected to your equipment through a circuit breaker. 7) Connect the power source last. 8) Disconnect the power source first. 9) When using a multiple range meter always use the high range first to determine the feasibility of using a lower range. 10) Check the current rating of all rheostats before use. Make sure that no current overload will occur as the rheostat setting is changed. 11) Never overload any electrical machinery by more than 25% of the rated voltage or current for more than a few seconds. 12) Select ratings of a current coil (CC) and potential coil (PC) in a wattmeter properly before connecting in a test circuit. 13) Never make wiring changes on live circuits. Work deliberately and carefully and check your work as you proceed. EED/EE305-EMLAB-1/CHR iii 14) When making measurements, form the habit of using only one hand at a time. No part of a live circuit should be touched by the bare hand. 15) Keep the body, or any part of it, out of the circuit. Where interconnecting wires and cables are involved, they should be arranged so people will not trip over them. 16) Be as neat a possible. Keep the work area and workbench clear of items not used in the experiment. 17) Always check to see that the power switch is OFF before plugging into the outlet. Also, turn instrument or equipment OFF before unplugging from the outlet. 18) When unplugging a power cord, pull on the plug, not on the cable. 19) When disassembling a circuit, first remove the source of power. 20) No ungrounded electrical or electronic apparatus is to be used in the laboratory unless it is double insulated or battery operated. 21) Keep fluids, chemicals, and beat away from instruments and circuits. 22) Report any damages to equipment, hazards, and potential hazards to the laboratory instructor. 23) If in doubt about electrical safety, see the laboratory instructor. Regarding specific equipment, consult the instruction manual provided by the manufacturer of the equipment. Information regarding safe use and possible- hazards should be studied carefully. EED/EE305-EMLAB-1/PS iv  NATIONAL INSTITUTE OF TECHNOLOGY, WARANGAL DEPARTMENT OF ELECTRICAL ENGINEERING ELECTRICAL MACHINES LABORATORY INSTRUCTIONS A. DRESS CODE: 1. Students should not wear loose and flowing robes while conducting experiments in the electrical machines laboratory. They should also avoid bathroom slippers and wear appropriate footwear. B. PREPARATION FOR THE LABORATORY: 2. A student must be well prepared for the experiment he/she is going to conduct in the laboratory. He/she should carry an observation notebook, which is exclusively meant for the laboratory. The following items must be clearly written/drawn/ indicated pertaining to the experiment that is being conducted: a) Aim of the experiment b) Apparatus needed c) A neatly drawn circuit diagram d) The fixation of the type and range of various meters e) Precautions f) Procedure g) Tables for observations h) Model calculations i) Expected graphs 3. It is mandatory for students to carry calculators and graph sheets along with the observation notebook. 4. Students must also bring the folder pertaining to the previous experiment, failing which their entry into the laboratory is summarily rejected. C. DURING THE LABORATORY SESSION: 5. Upon entering the lab, the faculty judge the preparedness of students by posing questions related to the experiment with due emphasis on the procedure, precautions, and the theory behind the experiment. 6. The students are expected to fix the type and ranges of the meters. In case it is already indicated in the manual (correctly), they are expected to justify them. EED/EE305-EMLAB-1/PS v  7. Students are permitted to carry out the experiment only after answering all the questions posed by the faculty members. In case they don’t, they are given one more chance to ponder over the questions and get back to the faculty. 8. Upon getting the clearance from the faculty, students are expected to fill out the indent form to draw the meters and components from the stores. 9. The students are then expected to make tight connections. The correctness of these connections is then verified by the faculty. 10. Faculty may choose to pose further questions to students at the test bench to judge their confidence levels and presence of mind during the experiment. 11. Students/faculty are expected to verify the general settings pertaining to the experiments before the start of experiments. These typically include the position of starters, field regulating rheostats, positions of autotransformers, loading rheostats, etc.,. 12. The experiment is then conducted according to the procedure described in the manual. 13. Care is exercised while taking measurements. Students should note zero errors in the meters (if any) before taking the readings. They should take the readings without parallax error and they should avoid leaning on to panels /loading rheostats and co-students. D. AFTER CONDUCTING THE EXPERIMENT: 14. Students show the observations to the faculty and upon their approval, proceed to make the required calculations. 15. Students are then expected to draw pertinent graphs and then show them to the faculty. 16. If any abnormalities are found, students may have to verify the veracity of the observations/calculations. E. AFTER THE LABORATORY SESSION: 17. Students are expected to document the experiment in the form of a folder. The format of the folder is well described in the manual. The folder, which is complete in all respects must be submitted in the subsequent session. EED/EE305-EMLAB-1/PS vi  GENERAL ELECTRICAL SYMBOLS Resistor Variable Resistor Potentiometer Light Dependent Resistor (LDR) Inductor Variable Inductor Transformer (laminated iron core) Autotransformer Polarised capacitor Unpolarised capacitor Alternating Current source Direct Current source EED/EE305-EMLAB-1/PS vii  Cell Battery Voltmeter Ammeter Single Pole Single Throw (SPST) switch Single Pole Double Throw (SPDT) switch Double Pole Single Throw (DPST) switch Double Pole Double Throw (DPDT) switch M G Motor Generator Wire (connection/joint) Crossing wires (no connection) Bell Lamp EED/EE305-EMLAB-1/PS viii  Fuse Circuut Breaker Buzzer Push Button (Normally Open) RPM Push Button (Normally Closed) Tachometer Ohmmeter Chasis Ground Equipotential Earth Ground EED/EE305-EMLAB-1/PS ix Expt-1 DETERMINATION OF OPEN CIRCUIT CHARACTERISTICS OF A DC MACHINE AIM: To obtain the magnetization characteristics of a DC machine by conducting no load test and to calculate its critical speed. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) Three point starter must be in OFF position. 2) Motor field rheostat must be in minimum resistance position. 3) Generator field rheostats must be in maximum resistance position. 4) Speed must be maintained constant throughout the experiment. PROCEDURE: 1) Connections should be made as per the circuit diagram. 2) Switch ON the supply using DPST switch and adjust the 3-point starter from its OFF position to ON position; slowly, smoothly and continuously. 3) Measure the speed of motor using tachometer. If the speed is less than the rated speed, adjust the field regulator (rheostat) in the motor to obtain the rated speed. 4) Adjust the field regulator (rheostat) of generator and note down the generated voltage across the armature. 5) In steps of 0.1 ampere, generator field rheostats are adjusted alternatively till we get 1.25 times the rated voltage across armature of the DC shunt generator. 6) Generated voltage across the armature under no field excitation (due to residual magnetism) should also be tabulated. 7) Generator field rheostat should be adjusted to maximum resistance position. Reduce the speed by adjusting the motor field rheostat to minimum resistance position and then the supply is switched OFF. EED/EE305-EMLAB-1/PS 1  CIRCUIT DIAGRAM FOR DETERMINATION OF OPEN CIRCUIT CHARACTERISTICS OF A SEPARATELY-EXCITED DC GENERATOR 3 - Point starter Fuse + L Z A A A Field Rheostat D + P Z 220 V M G S V DC Supply T Mechanical coupling ZZ AA AA Fuse + A Fuse D + Z P Generator V Field S Winding T ZZ Fuse EED/EE305-EMLAB-1/PS 2 OBSERVATION TABLE: 𝒗 S.No If (ampere) Vg (volt) Vf (volt) Rf= 𝑰 𝒇 ohms 𝒇 𝑅𝑓1 +𝑅𝑓2+⋯ 𝑅𝑓𝑛 Average Rf = ohm 𝑛 MODEL GRAPH: Vg (volts) y x Residual Voltage If (amps) 𝑦 = 𝑠𝑙𝑜𝑝𝑒 = 𝑅𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝑥 From graph, Rcritical is obtained. Rf is obtained from observation Nrated is from name plate design 𝑁𝑟𝑎𝑡𝑒𝑑 ∗ 𝑅𝑓 = 𝑅𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 X 𝑁𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 ; 𝑁𝑟𝑎𝑡𝑒𝑑 𝑋 𝑅𝑓 𝑁𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 = 𝑅𝑐𝑟𝑖𝑡𝑖𝑐𝑎𝑙 RESULT: EED/EE305-EMLAB-1/PS 3 Expt-2 DETERMINATION OF LOAD CHARACTERISTICS OF A DC GENERATOR AIM: To obtain the internal and external characteristics of a dc shunt generator by conducting load test on it. APPARATUS REQUIRED: S.No Name of Apparatus Type Range Quantity PRECAUTIONS: 1) The DPSTs (motor side and generator side) should be in OFF position. 2) Motor field rheostat must be in minimum resistance position. 3) Generator field rheostats must be in maximum resistance position. 4) Speed must be maintained constant throughout the experiment. PROCEDURE: 1) Connections should be made as per the circuit diagram. 2) Switch ON supply and adjust the 3-point starter from OFF position to ON position; slowly, smoothly and continuously. 3) Measure the speed of motor using tachometer. If the speed is less than the rated speed adjust the field regulator of motor to get rated speed. 4) The speed of the motor-generator set should be maintained constant throughout the experiment. 5) Adjust the generator field regulator to obtain rated voltage across its armature terminals. If the generator is not able to build up, interchange the field terminals of generator. 6) After obtaining rated voltage across generator terminals and speed of generator is at rated speed, switch ON the load side DPST. 7) The load is gradually increased by turning ON the switches on resistive load bank and at each load condition VL, IL and IF must be noted. 8) Note down the readings till the full-load current flows in generator circuit. 9) The load on the generator is reduced to zero and turn-OFF the load side DPST. EED/EE305-EMLAB-1/PS 4  CIRCUIT DIAGRAM FOR DETERMINATION OF LOAD CHARACTERISTICS OF SELF-EXCITED DC SHUNT GENERATOR 3 - Point starter Fuse + L Z A + A A A + Field A D Rheostat + D P Z FR V P M G DC Supply S S T T L Mechanical Z O A coupling D ZZ AA AA ZZ Fuse EED/EE305-EMLAB-1/PS 5  CIRCUIT DIAGRAM FOR FINDING ARMATURE RESISTANCE OF THE GENERATOR Fuse + + A A D + P V G DC Supply S T AA Fuse EED/EE305-EMLAB-1/PS 6 10) The field regulator of the generator is brought down to its initial condition and then the motor field regulator should be adjusted to its initial condition. Then the supply is switched OFF. OBSERVATIONS & CALCULATIONS: VL IL If Ia=IL+If Eg=VL+IaRa S.No (volt) (ampere) (ampere) (ampere) (volt) OBSERVATION TABLE FOR FINDING ARMATURE RESISTANCE: V I 𝑽 S.No Ra= 𝑰 (𝐨𝐡𝐦𝐬) (volt) (ampere) 𝑅1+𝑅2+𝑅3+𝑅4 Average 𝑅𝑎 = ohm 4 MODEL GRAPH: Internal characteristics Voltage (Eg vs Ia) External Characteristics (VL vs IL) Current RESULT: EED/EE305-EMLAB-1/PS 7 Expt-3 SPEED CONTROL OF DC SHUNT MOTOR AIM: Obtain the speed control of DC shunt motor using armature voltage control method and field current control method. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: At the time of starting SPST switch must be closed and 3-point starter must be at off position. a) Armature voltage control method: i) Field current is maintained constant throughout this test. ii) Starter must be off position at the time of starting. b) Field current control method: i) Voltage across armature is maintained constant through this test. PROCEDURE: a) ARMATURE VOLTAGE CONTROL METHOD: 1) SPST switch is closed and field regulator must be minimum position. 2) Switch on supply and start the motor using 3-point starter. 3) Measure the speed of the motor. If it is not running at rated speed, adjust the field regulator of motor to run the motor at rated speed. 4) Note down the field current reading which is maintained constant. 5) Open SPST switch and adjust the drum type rheostat to obtain variation in voltage across armature of motor. 6) For each voltage armature, measure the speed of the motor. EED/EE305-EMLAB-1/PS 8  CIRCUIT DIAGRAM FOR SPEED CONTROL OF DC SHUNT MOTOR 3 - Point starter Fuse + L Z A A Field Rheostat + M V D + Z P DC Supply S V T AA ZZ + SPST Rheostat A Fuse EED/EE305-EMLAB-1/PS 9 b) FIELD CURRENT CONTROL METHOD: 1) Adjust the drum type rheostat to bring bit to minimum resistance position. 2) Measure the speed of the motor, if it is not running at rated speed, adjust the field regulator to get rated speed. 3) Adjust the drum type rheostat to keep voltage across armature around 200 V. Then this voltage is maintained constant. 4) Adjust the field regulator motor in very small step variation and note down the speed in all conditions. 5) Limit the speed of the motor to 25% above the rated speed, failing which the motor may damage due to centrifugal forces. 6) Bring the motor to normal speed and then switch off. 7) Keep the starter in off position. OBSERVATIONS: TABULATION FOR ARMATURE VOLTAGE CONTROL METHOD If =_______________ S.No Va (volt) N (rpm) TABULATION FOR FIELD CURRENT CONTROL METHOD Va = ________________ S.No If (volt) N (rpm) RESULT: EED/EE305-EMLAB-1/PS 10 Expt-4 BRAKE TEST ON A DC SHUNT MOTOR AIM: To determine the efficiency of a DC shunt motor by conducting brake test on it. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) Motor field regulator must be in minimum resistance position. 2) There should not be any load on the motor. PROCEDURE: 1) Connections are given as per the circuit diagram. 2) After checking the minimum position of field rheostat, DPST switch is closed and starting resistance is gradually removed using 3-point starter. 3) By adjusting the field rheostat, the machine is brought to its rated speed. 4) Record the armature current, field current and voltage readings at no load. 5) Load the motor using spring balance arrangement in steps from no load to full load and note the corresponding readings. 6) After taking all the readings, readjust all to their initial positions and switch off the DPST switch. EED/EE305-EMLAB-1/PS 11  CIRCUIT DIAGRAM FOR BRAKE TEST ON A DC SHUNT MOTOR 3 - Point starter Fuse + + L Z A A S1 S2 Field Rheostat A D + Z P V DC Supply S M T ZZ AA Brake drum arrangment Fuse EED/EE305-EMLAB-1/PS 12 OBSERVATIONS: TABULATION FOR BRAKE TEST ON A DC SHUNT MOTOR: Input Output V IL SPEED S1 S2 W T Efficiency S. No. Power Power (volt) (A) (W) (rpm) (kg) (kg) (kg) (N-m) (W) (%) CALCULATION: a) Measure the circumference of the brake drum and calculate its radius (r), in meters. b) Calculate the torque, T = W r g (N-m); where W = [S1~S2] (kg), i.e. difference of spring balance readings; and ‘g’ is acceleration due to gravity i.e. 9.81 m/s2. c) Calculate the output power of the motor, P0 = 2πNT/60 (watt) d) Calculate the input power, PI = V IL (IL is the line current = Ia + If). e) Calculate the percentage efficiency, η = (P0/PI) x 100 MODEL GRAPHS: a) Output Vs (Efficiency, torque, armature current and speed). b) Speed Vs Torque. Efficiency Current Torque Speed Speed Output Torque RESULT: EED/EE305-EMLAB-1/PS 13 Expt-5 SWINBURNE’S TEST ON A DC MACHINE AIM: To conduct Swinburne’s test on dc machine to predetermine the efficiency when running as a motor and generator without actually loading the machine. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) Motor field regulator must be in minimum resistance position. 2) There should not be any load on the motor. PROCEDURE: 1) Connections are given as per the circuit diagram. 2) After checking the minimum position of field rheostat, DPST switch is closed and starting resistance is gradually removed using 3-point starter. 3) By adjusting the field rheostat, the machine is brought to its rated speed. 4) Note down the armature current, field current and voltage readings at no-load. 5) After taking all the readings, readjust all to their initial positions and turn-OFF the DPST switch. EED/EE305-EMLAB-1/PS 14  CIRCUIT DIAGRAM FOR SWINBURNE’S TEST ON A DC MACHINE 3 - Point starter Fuse + + L Z A A + Field A Rheostat A D + Z P DC Supply S V T ZZ M + A AA Fuse EED/EE305-EMLAB-1/PS 15  OBSERVATIONS: a) DC MACHINE OPERATING AS MOTOR: Total Output Input S. V IL Ia Ia2Ra Efficie Losses Power Power No. (volt) (ampere) (ampere) (watt) ncy W (watt) (watt) (watt) b) DC MACHINE OPERATING AS GENERATOR: IL Ia Total Output Input S. V Ia2Ra Efficie (amper (amper Losses Power Power No. (volt) (watt) ncy e) e) W (watt) (watt) (watt) CALCULATIONS: Hot Resistance Ra = (1.2 X R) Ω Constant losses = (VI0 – Ia02 Ra) watt Where Ia0 = (I0 – If) ampere DC MACHINE OPERATING AS MOTOR: Load Current IL = _____ ampere (Assume 25%, 50%, 75% of rated current) Armature current Ia = (IL – If) ampere Copper loss = (Ia2 Ra) watt Total losses = Copper loss + Constant losses Input Power = (VIL) watt Output Power = Input Power – Total losses %  Output power X 100% Input Power EED/EE305-EMLAB-1/PS 16 DC MACHINE OPERATING AS GENERATOR: Load Current IL = _____ ampere (Assume 25%, 50%, 75% of rated current) Armature current Ia = IL + If ampere Copper loss = Ia2 Ra watt Total losses = Copper loss + Constant losses Output Power = VIL watt Input Power = Input Power +Total losses %  Output power X 100% Input Power MODEL GRAPH: Generator Efficiency Motor Load Current RESULT: EED/EE305-EMLAB-1/PS 17 Expt-6 RETARDATION TEST ON A DC MACHINE TO DETERMINE THE MOMENT OF INERTIA AIM: To conduct retardation test on a DC shunt motor and to calculate its moment of inertia. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) Motor field regulator must be in minimum resistance position. 2) There should not be any load on the motor. PROCEDURE: 1) Connections are made as per the circuit diagram. 2) After checking the minimum position of field rheostat, and DPDT in position 1 & 1’, DPST is closed and starting resistance is gradually removed by using three-point starter. 3) By adjusting the field rheostat, the machine is brought to its rated speed. 4) Using DPDT switch change the position of the armature terminals from 1-1’ to 2-2’. Now the armature is disconnected from the main supply and the motor is allowed to retard. 5) Record time taken of 5% fall in speed, voltmeter and ammeter readings. 6) Open the DPST switch. EED/EE305-EMLAB-1/PS 18  RETARDATION TEST ON A DC SHUNT MOTOR TO DETERMINE THE MOMENT OF INERTIA 3 - Point starter Fuse + L Z A Field Rheostat A + D + Z + D P P A DC Supply S V M V D T T ZZ Resistive Load + AA A Fuse EED/EE305-EMLAB-1/PS 19 OBSERVATIONS: RETARTATION TEST Speed V I Time S. No. (rpm) (volt) (ampere) (sec) MODEL GRAPH: Speed Time RESULT: EED/EE305-EMLAB-1/PS 20 Expt-7 FIELD TEST ON TWO IDENTICAL DC SERIES MACHINES AIM: To determine the efficiencies of the given DC series generator and motor by conducting field test. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) The SPST switch should be open. 2) The field rheostat should be in maximum resistance position. 3) There should be some load on the generator (approximately 30% of full load). PROCEDURE: 1) Connections are given as per the circuit diagram. 2) Close the DPST switch; gradually bring the field rheostat to minimum resistance position and close the SPST switch. 3) Vary the load on the generator in steps and note down the meter readings and corresponding speed; maintaining constant voltage across the motor for each load. 4) Reduce the load on the generator to the initial value, open the SPST and bring back the field rheostat to maximum resistance position. 5) Open the DPST switch. MEASURE ARMATURE AND FIELD RESISTANCE OF THE MOTOR & GENERATOR: 1) Armature resistance, field resistance of the motor and generator are measured using low voltage supply. 2) Three sets of readings are taken for each resistance measurement, and its average is taken for calculation. EED/EE305-EMLAB-1/PS 21  CIRCUIT DIAGRAM FOR FIELD TEST ON A PAIR OF DC SERIES MACHINES + Field A Rheostat YY Fuse S Motor + Field Y + A A + V A D + + P V V M G DC Supply S T L Mechanical O A coupling D AA AA + Y Generator Fuse V Field YY EED/EE305-EMLAB-1/PS 22  CIRCUIT DIAGRAM FOR FINDING ARMATURE RESISTANCE OF THE MOTOR Fuse + + A A D + P V M DC Supply S T AA Fuse EED/EE305-EMLAB-1/PS 23  CIRCUIT DIAGRAM FOR FINDING ARMATURE RESISTANCE OF THE GENERATOR Fuse + + A A D + P V G DC Supply S T AA Fuse EED/EE305-EMLAB-1/PS 24 OBSERVATIONS: VS V1 A1 V2 A2 Speed S.No. (volt) (volt) (ampere) (volt) (ampere) (rpm) OBSERVATION TABLE FOR ARMATURE RESISTANCE OF MOTOR: V I 𝑽 S.No Ra= 𝑰 (𝐨𝐡𝐦) (volt) (ampere) 1 2 3 𝑅1+𝑅2+𝑅3+𝑅4 Avg: 𝑅𝑎 = ohm 4 OBSERVATION TABLE FOR ARMATURE RESISTANCE OF GENERATOR: V I 𝑽 S.No Ra= 𝑰 𝐨𝐡𝐦𝐬 (volt) (ampere) 1 2 3 𝑅1+𝑅2+𝑅3+𝑅4 Avg: 𝑅𝑎 = ohm 4 CALCULATIONS: Total losses = V3 I1 –V2 I2 =WT Motor copper losses = I12 (Rse + Ra )= WCU(M) Generator copper losses = I12 Rse + I22 Ra = WCU(G) Stray losses for 2 m/c s =WS = WT –WCU (M)–WCU (G) Stray losses for each machine= WS / 2 EED/EE305-EMLAB-1/PS 25 Total motor losses = WCU(M) + WS / 2 = WM Total generator losses = WCU(G) + WS / 2 = WG Motor input = V1I1 Motor output = (V1I1 -WM) Motor efficiency = motor output / motor input Generator output = V2I2 Generator input = V2I2 + WG Generator efficiency = generator output / generator input WM WG I1 I2 S. No m G (watt) (watt) (ampere) (ampere) Efficiency characteristics of motor and generator S. V1 I1 W1 V2 A2 W2 % %R No. (volt) (ampere) (watt) (volt) (ampere) (watt) %  for any load = W2 / W1 *100 % Regulation = V2(N.L) – V2 (L) / V2(N.L) *100 GRAPHS: 1. Output Vs  % 2. Load current Vs % Regulation RESULT: EED/EE305-EMLAB-1/PS 26 Expt-8 HOPKINSON’S TEST ON TWO DC SHUNT MACHINES AIM: To determine the efficiencies of DC shunt motor and generator by conducting regenerative test. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) The SPST switch should be in open condition before the motor is started. 2) The motor field rheostat should be in minimum resistance position and generator field rheostat should be in maximum resistance position. 3) Close SPST switch, when the voltmeter (V2) reads zero. PROCEDURE: 1) Connections are given as per the circuit diagram. 2) Close the DPST switch and adjust the motor speed to its rated value using motor field rheostat. 3) Observe the reading in voltmeter (V2). If it is zero, close the SPST. 4) If it is not zero, reverse the polarity of the field winding of generator and adjust generator field rheostat such that voltmeter (V2) indicates zero; now close the SPST switch. 5) Load the generator in steps by increasing the excitation. Note down the meter readings for every step of loading. 6) Reduce the load on the set gradually. 7) Open the SPST switch; bring motor field rheostat to minimum resistance position. 8) Measure the armature resistance of the motor and generator. EED/EE305-EMLAB-1/PS 27  CIRCUIT DIAGRAM FOR HOPKINSON’S TEST ON DC SHUNT MACHINES + V 3 - Point starter V2 Fuse + L Z A + A S + Field A A Rheostat + D Z + A A P DC Supply S V T Z ZZ M G + A Mechanical ZZ coupling AA AA Fuse EED/EE305-EMLAB-1/PS 28 OBSERVATIONS: Speed = V I1 I2 I3 I4 Motor Generator S.No. (volt) (ampere) (ampere) (ampere) (ampere) input output Motor armature resistance =r1 Ω Generator armature resistance= r2 Ω CALCULATIONS: Motor armature circuit copper losses = I 1 2 r1 Generator armature circuit losses = I22r2 Total iron and friction losses for two machines = VI- (I12r1+ I22r2) Iron and friction losses for one machine PD = [VI- (I12r1+ I22r2)] /2 Motor input power Pi1 = VI + Vi1 Motor losses PL1 = P0+I12r1+ Vi1 Motor output Power P01 = P11-PL1 Motor efficiency ηM = 1-(PL1/P11) Generator output power P02=VI2 Generator losses PL2= P0+I22r2+Vi2 Generator input power Pi2=P02+PL2 Generator efficiency ηG=1-(PL2/Pi2) GRAPHS: Plot efficiency characteristics for Motor and Generator RESULT: EED/EE305-EMLAB-1/PS 29 Expt-9 OPEN CIRCUIT AND SHORT CIRCUIT TESTS ON A SINGLE PHASE TRANSFORMER AIM: To predetermine the efficiency, regulation and equivalent circuit parameters of a 1-ø transformer by conducting OC and SC tests on it and also obtain the equivalent circuit parameters referred to low voltage and high voltage side. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1) The auto transformer should be in minimum voltage position. 2) The secondary of the transformer should be open (OC test). 3) The secondary of the transformer should be short circuited (SC test). PROCEDURE FOR OPEN-CIRCUIT TEST: 1) Connections should be made as per the circuit diagram. 2) Switch on the AC supply for 1ø; slowly adjust the auto transformer knob so that the applied voltage is equal to that of the rated voltage on primary side. 3) Note down the readings of ammeter, voltmeter and wattmeter. 4) Slowly reduce the voltage to ZERO and switch-OFF the AC supply. PROCEDURE FOR SHORT-CIRCUIT TEST: 1) Connections should be made as per the circuit diagram. 2) Switch on the AC supply for 1ø; slowly adjust the auto transformer knob so that the ammeter indicates the rated current which is full load current on primary side. 3) Note down the readings of ammeter, voltmeter and wattmeter. 4) Slowly reduce the voltage to ZERO and switch-OFF the AC supply. EED/EE305-EMLAB-1/PS 30  CIRCUIT DIAGRAM FOR OPEN-CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER W Ph Fuse CC M L A D C r PC V AC P S V Supply T N Fuse LV HV 1ɸ auto- transformer EED/EE305-EMLAB-1/PS 31  CIRCUIT DIAGRAM FOR SHORT-CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER W Ph Fuse CC M L A D C r PC V AC P S V Supply T Fuse HV LV N 1ɸ auto- transformer EED/EE305-EMLAB-1/PS 32 OBSERVATIONS FROM THE EXPERIMENTATION: OPEN-CIRCUIT TEST: V0 I0 W0 Input power (volt) (ampere) (watt) (W0*Kp) watt SHORT CIRCUIT TEST: Vsc Isc Wsc Input power (volt) (ampere) (watt) (Wsc*Kp) watt CALCULATIONS: 𝑊 W0=V0*I0*cosø0 power factor at no load cosø0 =𝑉 ∗𝐼0 0 0 𝑉 𝐻𝑉 2 Im=I0*sin ø0 X0=𝐼 0 X0'=X0*( 𝐿𝑉 ) 𝑚 𝑉 𝐻𝑉 2 IL=I0*cos ø0 R0= 𝐼 0 R0'=R0*( 𝐿𝑉 ) 𝐿 𝑉 𝑊𝑠𝑐 Zsc= 𝐼𝑠𝑐 Rsc=𝐼 2 𝑠𝑐 𝑠𝑐 𝐿𝑉 2 𝐿𝑉 2 Xsc=√𝑍𝑠𝑐 2 − 𝑅𝑠𝑐 2 Req’= Rsc*(𝐻𝑉) Xeq’= Xsc*(𝐻𝑉) 𝒙∗𝑲𝑽𝑨∗𝑷.𝑭∗𝟏𝟎𝟎𝟎 Efficiency (ɳ ) = 𝒙∗𝑲𝑽𝑨∗𝑷.𝑭∗𝟏𝟎𝟎𝟎∗𝒙𝟐 𝑾𝒔𝒄 ɳ at full load  substitute x=1 P.F at 1, 0.8 3 3 ɳ at 4 load  substitute x=4 1 1 ɳ at load  substitute x= 2 2 1 1 ɳ at 4 load  substitute x=4 EED/EE305-EMLAB-1/PS 33 REGULATION: 𝐼𝑠𝑐 𝑅𝑠𝑐 𝑐𝑜𝑠ø±𝐼𝑠𝑐 𝑅𝑠𝑐 𝑐𝑜𝑠ø Percentage regulation = 𝑉 V=230 V, assume P.F at 0.8, 0.6, 0.4, 0.2 & upf (lag & lead) [ (+) for lag angles and (—) for lead angles] TABLE FOR REGULATION: S.No LAG (or) LEAD Percentage regulation Percentage power factor during LAG regulation during LEAD 1 0.8 2 0.6 3 0.4 4 0.2 5 0 6 1 TABLE FOR EFFICIENCY: S.No Load (X) ɳ at u.p.f ɳ at 0.8 ɳ at 0.6 ɳ at 0.4 p.f p.f p.f 1 1 3 2 4 1 3 2 1 4 4 5 0 EED/EE305-EMLAB-1/PS 34 MODEL GRAPHS: % Load % Regulation 2 1 % 0 1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 -1 lag lead -2 RESULT: EED/EE305-EMLAB-1/PS 35 Expt-10 LOAD TEST ON A SINGLE PHASE TRANSFORMER AIM: To calculate the efficiency and regulation of a 1ø transformer by conducting load test on it. APPARATUS REQUIRED: S.No Name of the apparatus Type Range Quantity PRECAUTIONS: 1. The auto transformer should be in minimum voltage position. 2. The DPST-1 and DPST-2 switch should be open. 3. During the load test, primary voltage should be maintained constant. PROCEDURE: 1. Connections should be made as per the circuit diagram. 2. The DPST-1 switch is closed. Slowly adjust the variac so that the applied voltage is equal to that of the rated voltage on primary side. Note down the readings of various meters (V1, I1, W & V2) 3. Close the DPST-2 switch and gradually apply the loads by closing the switches one by one. Note down the readings of various meters (V 1, I1, W, V2, I2) at each stage. 4. Reduce the load on the transformer to zero position and open DPST-2. 5. Reduce the voltage of variac slowly to zero and open DPST-1. EED/EE305-EMLAB-1/PS 36  CIRCUIT DIAGRAM FOR LOAD TEST ON A SINGLE PHASE TRANSFORMER W1 Ph Fuse CC M L A A D C r PC V D L P P O AC S V V S A Supply D T T N Fuse 1ɸ auto- transformer EED/EE305-EMLAB-1/PS 37  OBSERVATION TABLE FOR LOAD TEST: V1 I1 W1 V2 I2 W2=V2*I2 𝑾𝟐 𝑽𝟎 −𝑽𝟐 S.No %ɳ= ∗ 𝟏𝟎𝟎 %reg= ∗ 𝟏𝟎𝟎 (volt) (ampere) (watt) (volt) (ampere) (watt) 𝑾𝟏 𝑽𝟐 MODEL GRAPH: % Load CALCULATIONS: Wattmeter Constant (K) 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑐𝑜𝑖𝑙 𝑟𝑒𝑎𝑑𝑖𝑛𝑔∗𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑐𝑜𝑖𝑙 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 K= 𝑁𝑜.𝑜𝑓 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 𝑉2 𝐼2 %ɳ = ∗ 100 = ∗ 100 𝑖𝑛𝑝𝑢𝑡 𝑊1 RESULT: EED/EE305-EMLAB-1/PS 38 Expt-11 SUMPNER’S TEST ON A SINGLE PHASE TRANSFORMER AIM: To determine the efficiency of a transformer by conducting Sumpner’s test. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1. The auto transformer should be in minimum voltage position. 2. The voltmeter (V3) may read zero due to inherent fault in it. It is always advisable to connect one of the transformer. PROCEDURE: 1. Make the connections as per the circuit diagram. 2. Apply the rated voltage to the primaries of transformers by adjusting the setting of auto transformer (AT1). 3. Check the voltage recorded by (V3). If it is zero, the secondaries are connected in series opposition. If it reads twice the secondary rated voltage the windings are not properly connected, then interchange the connections at the secondary terminals of the transformers. Close the switch ‘S’ after verifying that (V3) reads zero. 4. Vary the secondary current with the help of auto transformer (AT 2). 5. Record the readings for different values of secondary current. EED/EE305-EMLAB-1/PS 39  CIRCUIT DIAGRAM FOR SUMPNER’S TEST ON TRANSFORMERS W1 Ph Fuse CC S M L A C r V D PC V AC P V3 S V Supply T N Fuse 1ɸ auto- transformer-1 W2 Ph Fuse CC M L A D C r PC V AC P S V Supply T N Fuse 1ɸ auto- transformer-2 EED/EE305-EMLAB-1/PS 40 OBSERVATIONS: V1 I1 W1 V2 I2 W2 S.No (volt) (ampere) (watt) (volt) (ampere) (watt) CALCULATIONS: Core loss of each transformer = W1 / 2 = Wi Copper loss of each transformer = WCU = W2 / 2 Output of transformer = I2 * rated sec. voltage*power factor Input to the transformer = output +Wi + WCU output Efficiency  input I2 P.F Output Input Efficiency S.No Wi +WCU (ampere) (assumed) (watt) (watt) (%) RESULT: EED/EE305-EMLAB-1/PS 41 Expt-12 SEPARATION OF NO LOAD LOSSES OF A SINGLE PHASE TRANSFORMER AIM: To separate hysteresis and eddy current losses of a single phase transformer. APPARATUS REQUIRED: S.No Name of the apparatus Type Range Quantity PRECAUTIONS: 1. Motor field rheostat should be in minimum resistance position. 2. Alternator field rheostat should be in maximum resistance position. 3. The autotransformer should be at minimum voltage position. 4. Maintain V/F constant. PROCEDURE: 1. Start the DC motor by three point starter. 2. Adjust the speed of a DC motor for a particular frequency using N= 120*f/p, (where p is number of poles of alternator). 3. Excite the alternator and generate a suitable voltage supply to variac. 4. Adjust the variac output voltage such that V/F =0.8. 5. Note down the meter readings. 6. Bring the variac output voltage to zero. Reduce the excitation of alternator to zero. 7. Repeat the steps 2-6 for different speeds i.e., frequencies. 8. Stop the motor by pressing red button, and bring the starter to OFF position. EED/EE305-EMLAB-1/PS 42  CIRCUIT DIAGRAM FOR SEPARATION OF NO LOAD LOSSES OF A SINGLE PHASE TRANSFORMER W 3 - Point starter Fuse M CC L + L Z A A C2 A1 A C r PC V Field Mechanical Rheostat coupling D V V P Z M DC Supply S T C1 A2 ZZ AA B2 B1 LV HV 1-ph auto- transformer Fuse + A Fuse + D Z P Alternator DC Supply Field S Winding T ZZ Fuse EED/EE305-EMLAB-1/PS 43 OBSERVATIONS: V= volts, f= Hz, V/f = , N=120*f /p f N V = 0.8*f Wi S. No Wi /f (Hz) (rpm) (volt) (watt) CALCULATIONS: Wi =Wh +We  ( K h  Bmax 1.6  f )  ( K e  Bmax 2  f 2)  (K h * f )  (K e * f 2 ) (v/f constant) GRAPH: Plot graph for (Wi /f) (vs) f From graph: OA= Kh , BC/AB = Ke From any frequency Wi = Kh*f + Ke*f2 Where Kh*f = hysteresis loss Ke * f2 = eddy current loss RESULT: EED/EE305-EMLAB-1/PS 44 Expt-13 SCOTT CONNECTION AIM: To convert three phase system to two phase system with the help of Scott connection. APPARATUS REQUIRED: S.No Name of apparatus Type Range Quantity PRECAUTIONS: 1. The three phase auto transformer should be in minimum voltage position. 2. The load side SPSTs should be in open condition. PROCEDURE: 1. Connections are given as per the circuit diagram. 2. Close the TPST switch and apply rated voltage by using three phase autotransformer to the primaries of the two single phase transformers. 3. Note down the voltage of V1, V2, and V3 and observe for balanced two- phase ac supply. 4. Close the switches, SPST-1 and SPST-2, one after the other and apply note down the readings. 5. Gradually apply equal load to both the secondaries of the transformers and record the meter readings. 6. Remove the load in steps and open the SPST-1 and SPST-2 switches. 7. Adjust the three phase autotransformer to minimum voltage position and open the TPST switch. EED/EE305-EMLAB-1/PS 45  CIRCUIT DIAGRAM FOR SCOTT CONNECTION A1 S1 Fuse R A L T O 3ɸ P V2 V A AC S D Supply T AT A2 A Fuse Y A S2 3ɸ L AC V V1 O V3 V Supply A D Fuse A3 AM B A A N 3ɸ auto- transformer EED/EE305-EMLAB-1/PS 46 OBSERVATIONS: TABULATION FOR BALANCED TWO-PHASE SUPPLY: V1 V2 V3 S.No (volt) (volt) (volt) TABULATION FOR LOADED SECONDARIES OF THE TRANSFORMERS: AM AT A1 A2 A3 V1 V2 S.No (ampere) (ampere) (ampere) (ampere) (ampere) (volt) (volt) CALCULATIONS: Verify the vector sum of V1 and V2 should be equal to √2 V1 (or) √2 V2. RESULT: EED/EE305-EMLAB-1/PS 47  APPENDIX-A 1) TWO-POINT STARTER 2) THREE-POINT STARTER EED/EE305-EMLAB-1/PS I 3) FOUR-POINT STARTER 4) RESISTORS EED/EE305-EMLAB-1/PS II 5) RHEOSTAT CONNECTIONS 6) CAPACITORS EED/EE305-EMLAB-1/PS III 7) CAPACITOR TYPES 8) INDUCTORS TYPES EED/EE305-EMLAB-1/PS IV 9) CLASSIFICATION OF DC MACHINES 10) CLASSIFICATION OF TRANSFORMERS: EED/EE305-EMLAB-1/PS V 11) TRANSORMERS SYMBOLS EED/EE305-EMLAB-1/PS VI