EMEC 1 LAB Laboratory Manual

DEV BHOOMI INSTITUTE OF TECHNOLOGY CHAKRATA ROAD,NAVGAOUN MANDUWALA,UTTARAKHAND Programs: B.TECH. (Electrical and Electronics Engineering) EMEC 1 LAB Laboratory Manual PREPARED BY Saurabh Rajvanshi ASST.PROFESSOR, ELECTRICAL ENGINEERING DEPARTMENT 1

LIST OF EXPERIMENTS Electrical machine 1 Lab (PEE 352) 1. To obtain magnetization characteristics of a d.c. shunt generator 2. To obtain load characteristics of a d.c. shunt generator and compound generator (a) Cumulatively compounded (b) Differentially compounded 3. To obtain efficiency of a dc shunt machine using Swinburn s test 4. To perform Hopkinson s test and determine losses and efficiency of DC machine 5. To obtain speed control of dc shunt motor using (a) armature resistance control (b) field control 6. To obtain speed-torque characteristics of a dc shunt motor 7. To obtain speed control of dc separately excited motor using Conventional Ward-Leonard/ Static Ward Leonard method. 8. To study polarity and ratio test of single phase and 3-phase transformers 9. To obtain equivalent circuit, efficiency and voltage regulation of a single phase transformer using O.C. and S.C. tests. 10 To obtain efficiency and voltage regulation of a single phase transformer by Sumpner s test 2

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 1 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 3 LABORATORY Name & Code: PEE-352 EMEC 1Lab SEMESTER: III Experiment No-1 Theory and Concept Objective: To conduct an experiment on a D.C shunt generator and draw the magnetization characteristics (OCC) and to determine the critical field resistance and critical speed. Apparatus: - S. No Apparatus Type Range Qty 1 Voltmeter M.C 0-250/500V 1 2 Ammeter M.C 0-1/2A 1 3 Rheostats Wire 400 /1.7A 1 wound 4 Tachometer Digital 0-9999 1 Theory: Open circuit characteristics or magnetization curve is the graph between the generated emf and field current of a dc shunt generator. For field cur-rent is equal to zero there will be residual voltage of 10 to 12V because of the residual magnetism present in the machine If this is absent there the machine cannot build up voltage to obtain residual magnetism the machine is separately excited by a dc source from OCC we can get critical field resistance and critical speed. Critical field resistance: It is the resistance above which the machine cannot build up emf. Critical speed: It is the speed below which the machine cannot build up emf. 3

Circuit diagram: Procedure: 1. Connections are made as per the circuit diagram. 2. Start the motor and bring it to rated speed.. 3. The switch SPST is opened and If=0 4. For the different values of excitations (I f ) the generated voltage (Eg)from the voltmeter is taken at rated speed, with increasing and decreasing orders. 5. Calculate average Eg from increasing and decreasing orders. 6. A graph is drawn between Avg Eg & If. From the graph (OCC) Critical field resistance and critical speed are calculated. Observation: Sl. No. Field Current Generated Volgate 4

Graph: Critical field resistance (Rc) Field resistance (Rf) The maximum voltage the Generator can induce With this field resistance. Critical Speed = OA/OC = OR = OM = PQ/PR * N Result: Precaution: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 5

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 2 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 6 LABORATORY Name & Code: PEE-352 EMEC 1 lab SEMESTER: III Experiment No-2 Theory and Concept Objective: To conduct a load test on the given DC Shunt generator and to obtain the performance characteristics Apparatus required: 1 Ammeter 0-20A, MC 1 0-1A, MC 1 0-5A MC 1 2 Voltmeter 0-250V, MC 1 0-30V, MC 1 3 Rheostat 400 /1.7A 1 4 Rheostat 100 /5A 1 5 Load 3 Kw / 220V 1 6 Tachometer 1 5 Connecting wires Theory: By conducting load test on DC shunt generator we can get load characteris-tics i.e, Internal & External characteristics. By exciting the m/c, the field current increases and voltage build up. After the machine has attained 220V the rated load is switched on. With increase in load, the voltage will be dropped 6

Circuit diagram: Armature Resistance (Ra):- Procedure 1. Connections are made as per the circuit diagram. 2. Start the machine with the help of starter and bring to rated speed by vary-ing field rheostat of motor, then by varying field rheostat of the generator set the rated voltage of the generator.. Then close the DPST switch of the load and increase the load by step 0.125Kw, up to full load of the generator. 3. Note down all the meter readings at every step. 4. Do necessary calculations. 7

Observations: S I L, in I f, in Ia= I L +if V t in I a R a in E G = V t + I a R a no amps amps in amps volts volts in volts Graph: Result: Between Emf Generated (E) and Current (I) Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 8

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 3 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 9 LABORATORY Name & Code: PEE-352 EMEC 1 Lab SEMESTER: III Theory and Concept Objective: To conduct load test on DC compound generator and to determine its characteristics Apparatus: S. No Equipment Range Type Qty 1. Voltmeter 0-250 V M.C. 1 2. Ammeter 0-2A M.C. 1 0-20A M.C. 1 3. Rheostats 400 /1.7A Wire wound 2 4. Tachometer Digital 1 5 Connecting wires Theory: D.C. Compound generator consists of both series and shunt field wind-ings. The shunt and series fields can be connected in two ways. 1. Short shunt. 2. Long shunt. When the MMF of series field opposes the MMF of shunt field, the generator is differentially compound. The terminal voltage decreases sharply with in-creasing load current. Evidently this connection is not used. In cumulative compound the connections of the two fields are such that their MMF s added and help each other. If the series field is very strong, the termi-nal voltage may increase as the load current increases and it is called over com-pounding. When terminal voltage on full load and no load are equal, it is known as flat compounded generator. If the series field is not strong, the terminal voltage will decreases with increase in load current (under compound) 9

Circuit diagram for cumulative compound generator: Procedure: 1. Connections are made as per the circuit diagram. 2. The machine is run at rated speed and the rated voltage is obtained by vary-ing field excitation 3. There the switch is closed so that load is connected across the generator. 4. Increase the load step by step with 0.125Kw and note down all the meter readings and calculations are made accordingly and the characteristics are obtained. 5. Plot graph for internal external characteristics. Observations: 10

Graph: Internal characteristics External characteristics Result: 11

Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 12

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 4 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 133 LABORATORY Name & Code: PEE-352 EMEC 1Lab SEMESTER: III Theory and Concept Object: To perform Swinburne s Test or no load test on dc motor and to predetermine the efficiencies of the machine acting as a motor and generator Apparatus: S.No Apparatus Type Range qty 1 Voltmeter MC 0-250v 1 2 Voltmeter MC 0-30V 1 3 Ammeter MC 0-5A 1 4 Ammeter MC 0-2A 1 5 Rheostats Wire wound 400 /1.7A 1 Wire wound 100 /5A 1 THEORY: It is simple indirect method in which losses are measured separately and the efficiency at any desired load can be predetermined. This test applicable to those machines in which flux is practically constant i.e. shunt and compound wound machines. The no load power input to armature consist iron losses in core, friction loss, windage loss and armature copper loss. It is convenient and economi-cal because power required to test a large machine is small i.e. only no load power. But no account is taken the change in iron losses from no load to full load due to armature reaction flux is distorted which increases the iron losses in some cases by as 50% Model calculations: No load input=v I L No load armature copper losses =Ia 2 Ra =(I l I f ) 2 Ra Constant losses Wc=V l (I l -I f ) 2 Ra Efficiency as a motor: I= Assumed load current Motor i/p=vi Ia=I L -If Motor armature losses=i 2 a.ra Total losses=i 2 a R a + Wc Efficiency of motor= VI- I 2 a R a + Wc / VI x 100 13

Efficiency as generator: I=assumed load current Generator O/P =VI Generator armature cu. Losses= I 2 a.ra Total losses= I 2 a R a + Wc Efficiency of generator=vi / VI+ I 2 a R a + Wc Circuit diagram: Procedure: 1. Make connections as per the circuit diagram. 2. Show the connections to the lab instructor. 3. Keeping both rheostats at minimum, Start the motor with the help of starter and by adjusting field rheostat bring the motor to rated speed. 4. Note down all the meter readings at no load. 5. Do necessary calculations and find out the efficiency of the Machine as a motor and as a generator 6. Draw the graphs between output Vs efficiency of the Machine as a generator and as a motor. 14

Observations: S.No I L I F I A V N(Speed) For Ra S.NO V I Ra=V/I Expected graphs:- Tabular Column to find out efficiency: GENERATOR: S.No Voltage Load Armature Armature Total losses Input- Output- η= in volts Current Current Ia = Cu loss= Wt=Wc+ VxIL Input-total Output/ in amps (IL+If) Ia XIaXRa IaXIaXRa losses= Input. VxIL-Wt 15

Motor: S.No Voltage Load Armature Armature Total losses Output= Input=output η= in volts Current Current Cu loss= Wt=Wc+ VxIL +total loss- Output/ in amps Ia =(IL-If) Ia XIaXRa IaXIaXRa es= Input. VxIL+Wt Results: Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 16

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 5 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 17 LABORATORY Name & Code: PEE-352 EMEC 1 Lab SEMESTER: III Theory and Concept Object: To conduct a Hopkinson s test on a two similar D.C shunt machines and find out the efficiency Apparatus: S.No Equipment Range Type Qty 1 Volt meter 0-250V M.C. 1 2 Ammeter 0-20A M.C 2 0-2A M.C 2 3 Rheostat 400 /1.7A Wire wound 2 4 Connecting wires THEORY: - Hopkinson s test is also called as regenerative test or back-to-back test. It is an indirect test or full test, which is used to determine the efficiency of the two identical shunt machines. The two machines are mechanically coupled and are also adjusted electrically that are of then run as motor and other as a generator. The two-shunt machines are connected in parallel. The power input from the mains is only that needed for supplying the losses of the two machines. The two machines can be tested under full load conditions (for determining the efficiency and maxi-mum temperature rise). 17

Circuit Diagram: Armature Resistance (Ra):- Procedure:- 1. Connected the circuit as per the circuit diagram. 2. Keep the field regulator minimum resistance position and start the motor by using starter, Keeping S.P.S.T switch open. 3. Adjust the regulator on generator side until the rated voltage equal to both in magnitude and polarity as that of main supply. i.e; voltmeter reads zero. 4. The S. P. S.T switch is closed to parallel the machines, by adjusting the re-spective field regulators, any load can now be thrown on to machines. 5. Calculate efficiency by applying load.(changing excitation) 18

Observation: Input Volt- Input Cur- Gen If=I 3 S. No age in volts Gen Ia=I 2 Motor If=I 4 rent=i 1 To find out efficiency: Motor: S. No Motor Motor Motor Stray Total Out put η of Moinput Armature Field loss losses Of Mo- tor Cu loss Cu loss of mo- tor tor Generator: S. Generator Generator Generator Stray Total Input η of No output Armature Field Cu loss losses of Of generator Cu loss loss generator generator Calculations: Armature Resistance of each machine =Ra Generator Armature cu loss =I 1 x I 2 x Ra Watts. Motor Armature cu loss Armature power input to the set. =V L x I 1 Watts. Ps, Stray losses of both machines (Gen +Motor) Stray losses of each machine = Ps/2 = (I 1 + I 2 )(I 1 + I 2 )Ra Watts. = V L x I 1 Armature Cu loss of Efficiency of Generator: Generator output Generator Losses Pg Efficiency of Generator = V L. I 2 Watts = V.I 3 + I 2 x I 2 +(Ps/2) =( V L.I 2 )/ (V L.I 2 +Pg) Efficiency of Motor : Motor in put: =VL (I1 +I2 +I4). Motor losses Pm =(I 1 +I 2 )(I 1 +I 2 )Ra +VxI 4 +Ps/2. Motor Efficiency = {VL (I1 +I2+I4)}-Pm/ VL (I1+I2+I4) 19

Plot the following graphs:- (a) Output Vs Efficiency for Generator. (b) Output Vs Efficiency for Motor. Model graphs:- Result: Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 20

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 6 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 21 LABORATORY Name & Code: PEE-352 EMEC I Lab SEMESTER: III Theory and Concept Object: To conduct speed controls on DC shunt motor. The methods are 1. Armature voltage control method 2. Flux control method Apparatus required: THEORY: S.No Equipment Range Type Qty 1 Ammeter 0-5A MC 1No 0-2A MC 1No 2 Voltmeter 0-250V MC 1No 3 Rheostats 100 /5A Wire wound 1NO 400 /1.7A Wire wound 1No 4 Tachometer 0-2000rpm Digital 1No 5 Connecting Wires LS i) Armature voltage control method: For a load of constant Torque, the speed is proportional to the applied to the arma-ture. Therefore speed voltage characteristic is linear and is a straight line. As the voltage is decrease across the armature the speed falls. This method gives speeds less than rated speeds. E b α ΦN E b α N V-Ia(Ra+R) α N As the voltage are decreased speed decreases. ii) Flux Control Method: With rated voltage applied to the motor, the field resistance is increased i.e field current is decreased. I t is observed that speed increases. E b /Φ α N N α E b /I f The characteristics If Vs N is inverse (or) if it is hyperbola. 21

Circuit diagram: Armature Resistance (Ra):- 22

Procedure: i) Armature Voltage Control Method. 1) Make connections as per the circuit diagram. 2) Show the connections to the lab instructor. 3) Keeping both rheostats at minimum, Start the motor with the help of starter and by adjusting field rheostat bring the motor to rated speed. 4) By increasing armature circuit rheostat in steps note down voltage, Ia and speed at every step. 5) The corresponding graph is draw between armature Voltage Vs speed ii) Flux Control method: 1) The machine run at its rated speed and rated voltage obtained. 2) The voltage is kept constant and for different values of field current the speed is noted. Observation Table: Armature Voltage Control Method S.No Armature Armature Speed Eb=V-IaRa in Voltage in current=ia in RPM volts volts in amps Flux Control Method: S.No Field Current in amps Speed in RPM Graphs: N (Speed) Vs If (Field Current) 23

N vs Va (Armature voltage) Result: Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 24

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 7 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 25 LABORATORY Name & Code: PEE-352 EMEC I Lab SEMESTER: III Theory and Concept Object: To conduct OC &SC tests on the given 1- Transformer and to calculate its 1) Equivalent circuit parameters a).referred to H.V side b).referred to L.V side 2) Efficiency at various loads. 3) Regulation at various power factors 4) Maximum Efficiency. Nameplate Details: 1 φ- TRANSFORMER T/F LV side HV side Rated power Rated voltage Rated current Frequency Apparaturs Required: SL.NO Name of the Apparatus Type Range Quantity 1 Ammeter MI 2 Ammeter MI 3 Voltmeter MI 4 Voltmeter MI 5 Wattmeter EDM(LPF) 6 Wattmeter EDM(UPF) 7 Single phase variac 25

Theory: Open Circuit (OC) or No-Load Test: The purpose of this test is to determine the shunt branch parameters of the equivalent circuit of the transformer. One of the windings is connected to supply at rated voltage, while the other winding is kept open -circuited. From the point of view of convenience and availability of supply the test is usually performed from the LV side, while the HV side is kept open circuited. Voltage =V1; Current =I0and power input=p0 Indeed the no-load current, I0is so small (itisusually2-6% of the rated current) and R01 and X01are also small, that V1can be regarded as = E1by neglecting the series impedance.thismeansthatforallpracticalpurposesthepowerinputonno-load equals the core(iron)lossi.e., P0=V1 I0 cos 0 cos 0 = P0/V1I0 Iw=I0 cos 0, =I0sin 0 R0=V1/Iw, X0=V1 / I Short Circuit (SC) Test: This test serves the purpose of determining the series parameters of a transformer. For convenience of supply arrange mentioned voltage and current to be handled, the test is usually conducted from the HV side of the transformer while the LV side is short-circuited. Since the transformer resistance and leakage reactance are very small, the voltage Vsc needed to circulate the full load currentundershortcircuitisaslowas5-8%of the rated voltage. The exciting current under the second it ions is only about 0.1to0.5%of the full load current. Thus the shunt branch of the equivalent circuit can be altogether neglected. While conducting the SC test, the supply voltage is gradually raised from zero till the transformer draws full load current. The meter readings under these conditions are: Since the transformer is excited at very low voltage, the iron loss is negligible (that is why shunt branch is left out), the power input corresponds only to the copper loss, i.e V sc =Voltage, I sc =Current, P sc =Power Copper loss) Z01= VSC/ ISC= R 2 01 + X 2 01 Equivalent resistance, R01=PSC/ (ISC) 2 Equivalent reactance, X01= Z 2 01-R 2 01 26

Circuit Diagram: Diagram--1 PROCEDURE: OC TEST: (1) All the connections are done as per the circuit diagram of OC test (2) Byusing1- variac apply rated voltage to the circuit. (3) At this rated voltage note down voltmeter, ammeter & wattmeter readings. (4) From the values we can find R0and X0 SC TEST: (1) All the connections are done as per the circuit diagram of SC test (2) By using1- variac apply rated voltage to the circuit. (3) At this rated current note down voltmeter, ammeter & wattmeter readings. (4) From this values we can find out R01&X01 27

TABULAR COLUMNS Observations: OC TEST: Vo (Volt) Io (Amps) Wo (Watts) SC TEST: Vsc (Volts) Isc (Amps) Wsc (Watts) Graphs: Result: Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 28

Dev Bhoomi Institute Of Technology Department of Computer Science & Engineering PRACTICAL INSTRUCTION SHEET LABORATORY MANUAL EXPERIMENT NO. 8 ISSUE NO. : ISSUE DATE: REV. NO. : REV. DATE : PAGE: 29 LABORATORY Name & Code: PEE-352 EMEC I Lab SEMESTER: III Theory and Concept Object: To convert three phase system to two phase system with the help of Scott Connection. Nameplate Details 1φ- TRANSFORMERS T/F Rated power T/F-1 T/F-2 HV side LV side HV side LV side Rated voltage Rated current Frequency Apparaturs Required: SL.NO Name of the Apparatus Type Range Quantity 1 Ammeter MI 2 Ammeter MI 3 Voltmeter MI 4 Voltmeter MI 5 Wattmeter EDM(LPF) 6 Wattmeter EDM(UPF) 7 Voltmeter MI 29

THEORY: Sumpner's test or back to back test on transformer is another method for determining transformer efficiency, voltage regulation and heating under loaded conditions. Short circuit and open circuit tests on transformer can give us parameters of equivalent circuit of transformer, but they cannot help us in finding the heating information. Unlike O.C. and S.C. tests, actual loading is simulated in Sumpner's test. Thus the Sumpner's test gives more accurate results of regulation and efficiency than O.C. and S.C. tests. Both transformers are connected to supply such that one transformer is loaded on another. Primaries of the two identical transformers are connected in parallel across a supply. Secondaries are connected in series such that emf's of that are opposite to each other. Another low voltage supply is connected in series with secondary s to get of them are connected in voltage opposition, i.e. E EF and E GH. Both the emf's cancel each other, as transformers are identical. In this case, as per superposition theorem, no current flows through secondary. And thus the no load test is simulated. The current drawn from V 1 is 2I 0, where I 0 is equal to no load current of each transformer. Thus input power measured by wattmeter W 1 is equal to iron losses of both transformers. i.e. iron loss per transformer Pi = W 1 /2. Now, a small voltage V 2 is injected into secondary with the help of a low voltage transformer. The voltage V 2 is adjusted so that, the rated current I 2 flows through the secondary. In this case, both primaries and secondary s carry rated current. Thus short circuit test is simulated and wattmeter W 2 shows total full load copper losses of both transformers. i.e. copper loss per transformer P Cu = W 2 /2. From test results, the full load efficiency of each transformer can be given as - 30

CIRCUIT DIAGRAM: Procedure: 1. The circuit is connected as per circuit diagram. 2. Both the transformers are energized at rated voltage & frequency. 3. With the secondary open, noted down the readings of W 1 which gives core loss. 4. Secondary is connected in phase opposition and checked trough voltmeter connected across the secondary. 5. Voltage is induced in secondary with help of booster transformer which is connected to source. Readings of W 2 are noted down. Observation: S.NO W1 W2 31

Formule: Graph: Result: Precautions: 1. Make Sure that your connection are correct. 2. Do not touch the live wire. 3. Take observation carefully. 4. Experiment kit should be properly grounded. 32