G.Pulla Reddy Engineering College (Autonomous): …gpreceels.co.in/files/et.pdf · O.C and S.C tests on single – phase transformer 5. Brake test on Three – phase squirrel –

G.Pulla Reddy Engineering College (Autonomous): Kurnool

Department of Electrical & Electronics Engineering

Electrical Technology Lab

List of Experiments GPREC/DEEE/EEE

Date: 29-06-2017

Page 1 of 1

Prepared by: Approved by: Revision No: 1

Sri.G. Sreenivasa Reddy Dr. T.Bramhananda Reddy

HOD, Dept.of EEE

1. Swineburne's test

2. Brake test on D.C. Shunt Motor

3. OCC of D.C. Shunt Generator

4. O.C and S.C tests on single – phase transformer

5. Brake test on Three – phase squirrel – cage induction motor

6. Determination of voltage regulation of 3 – phase alternator by

synchronous impedance method

Safety Precautions:

1. Ensure appropriate attires: no slippers, sandals or open-toe footwear allowed.

2. Long hair should be properly tied.

3. Make sure hands are dry when conducting experiment. "KEEP WATER BOTTLES AWAY

FROM EXPERIMENT AREA".

4. Make sure all power supplies are switched off before commencing with connections.

5. Make circuit connections with test leads. Use only ONE hand when making connections to

avoid closing circuit with your body.

6. Signal tutor or technician to check and verify your wire connections are correct.

7. Switch on power supply and proceed with data collection for experiment.

8. After each set of readings, switch off power supply before making any changes to wire

connections.

9. When disconnecting test leads, remove the main power supply connections first, i.e. DC

positive voltage output or AC voltage live output.

Learning objectives:

The Significance of Electrical Machines is renowned in the various fields of Engineering.

It is obligatory to have the practical idea about the Electrical Machines.

Students keeping in view the following objectives.

(1) To provide experience in experimental methods.

(ii) To provide experience in selecting and using variety of electrical instruments & accessories.

(iii) To reinforce theoretical instructions with Related Practical’s.

(iv) To give practice in Machine circuit Connections.

(v) To Provide Training the Technical report writing.

Learning Outcomes

The student will:

1. Explain principles of operation of DC motors.

2. Summarize National Electric Code (NEC) regulations governing the installation of

transformers and AC/DC motors.

3. Identify the various terms associated with /DC motors.

4. Describe basic motor and generator parts as to their specific use and application.

5. Discuss troubleshooting techniques for motors, generators, and transformers.

6. Calculate motor horsepower, speed, slip, efficiency, power factor, and torque for

electrical machines.

7. Discuss motor losses at unloaded and loaded conditions.

8. Understand the principles and construction of D.C. machines.

9. Demonstrate an awareness of the sources of electrical energy and their sustainability;

10. Describe the construction and operation of simple electrical machines and use nameplate

data and equivalent circuits to determine electrical and mechanical performance;




Title : Swinburne’s Test GPREC/DEEE/EEE

Date: 29-06-2017

Page 1 of 5



HOD, Dept.of EEE

Objective:

To conduct Swinburne’s test on DC shunt machine and to pre determine its

efficiency.

Apparatus:

S.No Name of the Apparatus Type Range No. of required

1 Voltmeter MC (0-300)V 1

2 Ammeter MC (0-2)A 1

(0-5)A 1

3 Rheostat Wire wound 350Ω/1.1A 1

4 Tachometer 1

5 Connecting wires Required

6 SPST Switch 1

Name plate details :

Fuse rating:

Formulae used: No Load armature current = Iao

No Load input = VIao Watts

No Load armature Cu loss = Iao2

Ra

Constant losses of machine, Pc= VIao - Iao2

Ra +VIf

Where Ia = Armature current (at any load) Ra = Armature resistance

As Motor:

Load current = IL amps





Date: 29-06-2017

Page 2 of 5



HOD, Dept.of EEE

Field current = If amps

Armature cu loss= Ia2

Ra watts

Ia = IL - If

Constant losses of motor Pc= VIo - Ia2

Ra

= VIo – (IL - If )

2 Ra

Total losses, PL=PC+ armature ‘cu’ loss

Input power = V IL watts,

Output power = input-total losses=VIL-PL Watts

Efficiency = (output/input) * 100 = (VIL-PL / VIo)*100

As Generator:

Load current =IL amps,

Field current =If amps

Ia = IL + If

Armature cu loss= Ia2

Ra watts

Total losses, PL=PC+ Armature ‘cu’ loss

Output power =V IL watts

Input power=Output + total losses=VIL+PL Watts

Efficiency = (output/input) * 100 = (VIL+PL / VIo)*100

Theory: Testing of D.C. machines can be divided into three methods: (a) direct,

(b) regenerative, and (c) indirect. Swinburne’s Test is an indirect method of testing a D.C.

machine. In this method, the constant losses of the D.C. machine are calculated at no-load.

Hence, its efficiency either as a motor or as a generator can be pre-determined. In this

method, the power requirement is very small. Hence, this method can be used to pre-

determine the efficiency of higher capacity D.C. machines as a motor and as a generator.





Date: 29-06-2017

Page 3 of 5



HOD, Dept.of EEE

Procedure:

1. Connections are made as per the circuit diagram.

2. Motor field rheostat is kept in minimum position.

3. The SPST switch is kept in closed position on no load.

4. Supply is given & motor is started with the help of four-point starter.

5. The field rheostat is adjusted till the rated speed is achieved.

6. SPST Switch is opened and currents IL, IF & Voltmeter reading are noted.

Observations:

As a Motor:

V IL (A) IF(A) Ia = IL -

If PL

Input

(VIL)

Output

(VIL- PL)

Efficiency

(Output/input)

As a Generator:

V IL (A) IF (A) Ia = IL+

If PL

Output

(VIL)

Input

(VIL+ PL)

Efficiency

(Output/input)





Date: 29-06-2017

Page 4 of 5



HOD, Dept.of EEE

Graphs:

Result:

Remarks if any:





Date: 29-06-2017

Page 5 of 5



HOD, Dept.of EEE

Circuit Diagram:

D

P

S

T

230V

DC

Supply V

L LL F A A

A

Z

ZZ

A

AA

+ _

+

_

+

_

A1.1

350

+

_

G.PULLA REDDY ENGINEERING COLLEGE(Autonomous): KURNOOL DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

Title: Brake Test on DC Shunt Motor GPREC/DEEE/ECM

Date : 29-06-2017

Page 1 of 3

Prepared by: Approved by: Revision No : 1

Sri. G.Sreenivasa Reddy Dr.T.Bramhananda Reddy

HOD, Dept.of EEE

Objective: To conduct brake test on DC Shunt Motor and draw its performance curves .

Apparatus:

S.No Name of the Apparatus Type Range No.of required



(0-20)A 1


4 Tachometer 1


7 SPST Switch 1

Name plate details:

Fuse ratings:

Theory:

Procedure:

1) Circuit is connected as per the circuit diagram.

2) The motor Rheostat is kept at minimum position.

3) Ensure that initially there is no load on the motor.

4) Machine is started using the four-point starter and the speed of the motor is

adjusted to rated value by varying the motor field rheostat.

5) note down the readings at no load.

6) Load the motor by tightening the belt on the pulley and record the readings of

all the meters, speed and the readings of both the spring balances.

7) Repeat step 6 by increasing the load on the motor in steps, till the rated current

of the motor is obtained.

8) Remove the load gradually and then bring the motor rheostat starting position

(minimum) before stop the motor by switching off the supply.

Observations:

G.PULLA REDDY ENGINEERING COLLEGE(Autonomous): KURNOOL DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING


Date : 29-06-2017

Page 2 of 3



HOD, Dept.of EEE

Voltage

(V)

IL

(A)

Speed

(N)

(RPM)

Balance

Torque in N-M

T=(F1-F2) rg

O/p=2πNT

60

I/P=

V IL

η=

(o/p) /

(i/p) F1 F2

r = radius of brake drum g = acceleration due to gravity

Graphs:

Result:

Remarks if any:

G.PULLA REDDY ENGINEERING COLLEGE(Autonomous):

KURNOOL DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING


Date : 29-06-2017

Page 3 of 3



HOD, Dept.of EEE

Circuit Diagram:

D

P

S

T

+

220V

DC

Supply

_

Z

ZZ

AA

A

+ _

+

_

V

L LL F A A

350Ω

1.1A

G. Pulla Reddy Engineering College (Autonomous): Kurnool Department of Electrical & Electronics Engineering

Title: OCC of DC shunt Generator GPREC/DEEE/EEE

Date: 29-06-2017


Page 1 of 3


HOD, Dept.of EEE

Objective: To obtain the open circuit characteristics of the given DC shunt generator at its

rated speed and determine the Critical resistance and Critical speed.

Apparatus:





4 Tachometer 1


Name plate details:

Fuse ratings:

Theory:

Procedure:


2. Motor field rheostat is kept in minimum position.

3. Generator field rheostat is kept in maximum position.

4. D.C. Generator is driven at its rated speed with the help of prime mover (DC

shunt motor).

5. Gradually the field rheostat of generator is varied in steps to get field current in

steps and armature terminal voltage is measured in each step.

6. Step 5 is repeated till 120% of rated voltage is obtained.

7. Then, the field current of generator is decreased and the armature terminal

voltage is noted in each step.

8. The O.C.C curve is plotted



Date: 29-06-2017


Page 2 of 3


HOD, Dept.of EEE

Observations:

If (A) Vf (V) Va(V)

Forward Reverse Forward Reverse Forward Reverse

GRAPHS:

REMARKS IF ANY:

RESULT:

Air gap

Line OCC



Date: 29-06-2017


Page 3 of 3


HOD, Dept.of EEE

Circuit Diagram:

A

A

_

+

_

V

V

+

+

_

+

_

D

P

S

T

Z

Z

L LL F A

230V

DC

Supply

230V

DC

Supply

A

A

+

_

A

V V

ZZ

AA AA 350Ω

1.1A

350Ω

1.1A




Title : OC & SC TEST ON 1-Phase TRANSFORMER GPREC/DEEE/EEE

Date: 29-06-2017

Page 1 of 8



HOD, Dept.of EEE

OBJECTIVE: To conduct Open Circuit, Short Circuit test on a given (KVA rating)1-

transformer and find the efficiency and regulation.

APPARATUS:


1 Voltmeter MI (0-300)V 1

2 Ammeter MI (0-2)A 1

(0-5)A 1

3 1- auto transformer 230V/(0-270V) 1

4 1- Booster transformer 230V/(0-30V) 1

5 Watt meter UPF 75V/150V

5A

1

LPF 300V

2A

1


NAME PLATE DETAILS:

FUSE RATINGS:

THEORY:

PROCEDURE:





Date: 29-06-2017

Page 2 of 8



HOD, Dept.of EEE

O.C.TEST:

1) Connect the circuit as per the circuit diagram.

2) Rated voltage is applied to circuit on Low Voltage side with the help of

Auto Transformer.

3) High Voltage side is opened.

4) All Meter readings are taken open circuit voltage(Voc) ,open circuit current

(Ioc) and open circuit power (Woc)

5) bring the auto transformer zero position and switch off the supply.

S.C. TEST:

1) Connect the circuit as per the circuit diagram.

2) Rated Current (w.r.t the given KVA) is applied to circuit on High Voltage

side with the help of Booster Transformer with Low Voltage side short-

circuited.

3) All Meter readings are taken, as ISC, Vsc and Wsc

OBSERVATIONS:

O.C.TEST:

S.No Voltage (in Volts) No load current(in

Amps)

Power in watts

S.C.TEST:

S.No Voltage (in Volts) Rated current

current(in Amps)

Power in watts





Date: 29-06-2017

Page 3 of 8



HOD, Dept.of EEE

GRAPHS:





Date: 29-06-2017

Page 4 of 8



HOD, Dept.of EEE

SAMPLE CALCULATIONS:

Core loss: Wo = VoIo cos o

cos o = W0 / VoIo there by o = cos-1(Wo / Vo Io )

I = Io cos o (Amps) I = Io sin o (Amps)

Xo1 = X02 / K2

R0 =V0 / I

Xo = V0 / I

R02 = Wsc / Isc 2

Ro1 = -------

K2

Zo2 = Vsc / Isc





Date: 29-06-2017

Page 5 of 8



HOD, Dept.of EEE

Percentage Efficiency: for all loads and p.f.

Output Power (X) x KVA rating x 1000 x cos

Efficiency % = -------------------- = ------------------------------------------------

Input Power Output power + losses

(X) x KVA rating x 1000 x cos

= -------------------------------------------------------------

(X) x KVA rating x 1000 x cos + Wo + X2Wsc

Percentage Regulation: + = lagging

- = leading

(X) x Isc (Ro2 cos Xo2sin ) x 100

R% = --------------------------------------

V2

Xo2 = ( Zo2 - Ro2

2)1/2

V2

K= ------- = 2

V1





Date: 29-06-2017

Page 6 of 8



HOD, Dept.of EEE

Where X is the load and it is 1 for full load, ½ for half load, ¾ load, ¼ load etc..

and the power factor is, upf, o.8 p.f lag and 0.8 p.f lead

RESULT :





Date: 29-06-2017

Page 7 of 8



HOD, Dept.of EEE

CIRCUIT DIAGRAM:

O.C TEST:





Date: 29-06-2017

Page 8 of 8



HOD, Dept.of EEE

CIRCUIT DIAGRAM:

S.C TEST :

G.PULLA REDDY ENGINEERING COLLEGE(Autonomous) : KURNOOL

Department Of Electrical and Electronics Engineering

TITLE:BRAKE TEST ON 3- SQUIRREL CAGE INDUCTION MOTOR

GPREC/DEEE/ECE DATE: 29-0602017

________________________________________________________

Page 1 of 3

Prepared by: Approved by: Revision No. 1

Sri.G.Sreenivasa Reddy Dr.T.Bramhananda Reddy

HOD, EEE Dept

OBJECTIVE: To draw the performance characteristics of a 3- squirrel cage Induction

motor by conducting brake test.

APPARATUS:

S.No Apparatus Name Type Range Number of Required

1 3- Watt meter UPF 500V,10A 1

2 Voltmeter MI (0-500V) 1


4 Tacho meter 1

5 Connecting wires Required number

NAME PLATE DETAILS:

FUSE RATINGS:

THEORY:

PROCEDURE:


2. Close the TPST switch.

3. With the help of 3- auto transformer rated voltage is applied.

4. With Star-Delta starter, the squirrel cage induction motor is started under no load

condition , at this moment all the no load readings are noted.

5. With the help of spring balances the motor is mechanically loaded till maximum

load current is reached in different steps.

6. For different steps of load currents, all the meter readings are observe and tabulated.





________________________________________________________

Page 2 of 3



HOD, EEE Dept

CIRCUIT DIAGRAM:

OBSERVATIONS:

S.

No

Speed

in

rpm

V IL Watt

meter

reading

(W*Wc)

Spring

Balance

T=(T1-

T2)rg 60

2 NTOutPut

%

slip cos

T

1

T2

GRAPHS:

1. Output power Vs Efficiency

2. Output power Vs Torque

3. Output Power Vs Speed





________________________________________________________

Page 3 of 3



HOD, EEE Dept

4. Output Power Vs % Slip


1. 60

2 NTOutPut

in watts

2. Torque= 9.81*(T1-T2)*r in N-m , (where 'r' is the radius of brake drum)

3. % efficiency () = InPutPower

rOutputPoweX100

4. InPut Power =( W *watt meter constant) in watts

5. % Slip = (Ns-N)/Ns*100

RESULT:

G.PULLA REDDY ENGINEERING COLLEGE(Autonomous): KURNOOL Department of Electrical & Electronics Engineering

TITLE: REGULATION OF ALTERNATOR GPREC/DEEE/ECE

DATE: 29-06-2017

______________________________________________________ Page 1 of 3



HOD, EEE Dept

OBJECTIVE: To determine regulation of an alternator by Synchronous impedance

method.

APPARATUS:

S.No Apparatus Name Type Range Number of

Required


2 Voltmeter MI (0-300V) 1


4 Rheostat WW 350Ω / 1.1A 2

5 Tachmeter 1


number

NAME PLATE DETAILS:

FUSE RATINGS:

THEORY:

PROCEDURE:

O.C TEST:

1. Connections are made as per circuit diagram, Keep the motor side rheostat in

minimum position and generator side rheostat in maximum position.

2. DC supply is given to the motor and it is started with the help of four point

starter

3. The speed of motor is adjusted to its rated speed by using motor field rheostat.

4. Close the alternator field excitation DPST, and the field current is varied with

exciter circuit rheostat.

5. At different field currents, voltmeter readings are noted up to 120% of voltage.

6. After that , rheostat of exciter is brought to original position.

S.C. TEST:

1. TPST switch is closed.

2. The field rheostat is varied until full load current is obtained, If and Isc are

noted.

3. Graphs between If Vs Voc from OC test and If Vs Isc from Sc test are drawn



DATE: 29-06-2017

______________________________________________________ Page 2 of 3



HOD, EEE Dept

CIRCUIT DIAGRAM:


Eph =(Voc)ph on open circuit



DATE: 29-06-2017

______________________________________________________ Page 3 of 3



HOD, EEE Dept

'+' for lagging , and for leading p.f '-'

% Regulation = (Eph-Vph)/Vph)*100

where Eph=induced emf /phase

Vph=rated terminal voltage/ phase

Expected Graphs:

RESULT:

VIVA Questions

1. Define the term voltage regulation of Alternator.

2. What is the necessity for predetermination of voltage regulation?

3. Name the various methods for predetermining the voltage regulation of 3-phase Alternator.

4. How synchronous impedance is calculated from OCC and SCC?

5. What are the advantages and disadvantages of estimating the voltage regulation of an

Alternator by EMF method?

6. Why is the synchronous impedance method of estimating voltage regulation considered as

pessimistic method?

7. In what way does the ampere-turn method differ from synchronous impedance method

8. What are the test data required for predetermining the voltage regulation of an Alternator by

MMF method?

9. Why is the MMF method of estimating the voltage regulation considered as the optimistic

method?

10. What is critical field resistance?

11. What are the conditions to build up e.m.f?

12. What is critical speed?

13.Does voltage will be developed at zero field current

14.What are the reasons for failure of building up e.m.f in a DC generator?

15.What are different types of DC generators?

16. What is meant by prime mover?

17. Give the disadvantages of brake test?

18. What are the precautions taken while preparing brake load test?

19. Which method is the most economical method for calculating efficiency of a D.C shunt machine?

20. Give any two advantages of brake load test?

21. Give direct and indirect method of testing a D.C shunt machine

22. What are the different methods of calculating efficiency of D. C shunt machine?

23. Why transformer rating are in KVA but not in KW?

24. Why upf wattmeter are used in SC test and lpf wattmeter are used in OC test on transformer?

25. what is the purpose of 4 point starter?

Documents

G.Pulla Reddy Engineering College (Autonomous): …gpreceels.co.in/files/et.pdf · O.C and S.C tests on single – phase transformer 5. Brake test on Three – phase squirrel –