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QMP 7.1 D/F Channabasaveshwara Institute of Technology

(An ISO 9001:2015 Certified Institution)

NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka.

Department of Electrical & Electronics Engineering

ELECTRICAL MACHINES LABORATORY – 1

Lab Manual

15EEL37

B.E - III Semester

Lab Manual 2017-18

Name :__________________________________________________

USN :___________________________________________________

Batch : ___________________Section : ________________

Channabasaveshwara Institute of Technology (An ISO 9001:2015 Certified Institution)


Department of Electrical & Electronics Engineering


Lab Manual

Version 2.0

August 2017

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


Sub Code: 15EEL37 IA Marks: 20

Hrs/week: 03 Exam Hours: 03

Total Hours: 42 Exam Marks: 80

1. 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.



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.



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.

INDEX PAGE

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.

Sl. No. Name of the Experiment

Date

Man

ual M

arks

(Max

. 20

)

Rec

ord

Mar

ks

(M

ax. 1

0)

Sign

atur

e

(Stu

dent

)

Sign

atur

e

(Fac

ulty

)

Conduction Repetition Submission of Record

Average

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.

Caution

1. Do not play with electricity.

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.

‘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.



DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGG.

CONTENTS First Cycle Experiments

Expt. No. Title of the Experiment Page

No.

1 Regulation of Alternator by ZPF Method. 02

2 OC & SC Tests on 1-Ф Transformer. 08

3 Slip Test on Alternator. 14

4 Scott Connection. 18

5 Separation of hysteresis and eddy current losses in single phase transformer. 20

6 No-Load and Load characteristics of a DC - shunt generator. 24

7 Polarity test on 1-ф transformer. 30

Second Cycle Experiments

Expt. No. Title of the Experiment Page

No.

8 Polarity Test and connection of 3 single-phase transformers in star – delta, delta – delta and V – V (open-delta) connection under load. 32

9 Sumpner’s Test. 38

10 Performance of synchronous generator connected to infinite bus, under constant power and variable excitation & vice - versa. 42

11 Regulation of Alternator by EMF and MMF Method. 48

12 Parallel Operation of Two 1-Ф Transformers. 56

13 Power angle curve of synchronous generator. 60

Question bank. 65

Viva - voce Questions. 67

References. 69

Appendix. 70

15EEL37 : Electrical Machines Laboratory-I 2017-18

CIRCUIT DIAGRAM:

Tabular Column

1. Open Circuit Test 2. Short Circuit Test

Sl. No

If Amps

V0 Volts

VL Vph

If Amps ISC Amps


Dept. of EEE, CIT-Gubbi, 572 216 Page No.2

Experiment No. 01 Date: __/__/_____

REGULATION OF ALTERNATOR BY ZPF METHOD

Aim To determine the percentage regulation of an alternator by ZPF method or Potier

Triangle Method. Apparatus Required

Sl. No Particulars Range Type Quantity

01. Voltmeter 0 – 600 V MI 01

02. Ammeters 0-10/20A 0-1/2A

MI MC

01 01

03. Rheostats 0-750Ω,1.2A 0-38Ω,8.5A - 02

01

04. Watt meters 0 – 10/20 A, 0 – 600 V LPF 02

05. Tachometer - - 01

06. 3-phase Inductive Load - - 01

Procedure a. Open Circuit Test

1. Connections are made as shown in the circuit diagram (1.a)

2. Keeping the rheostat R1 in the field circuit of motor in cut-out position, the

rheostat R2 in the armature circuit of the motor and the rheostat R3 in field circuit

of the alternator in cut-in positions, and TPST (S2) in open position, the supply

switch (S1) is closed.

3. The motor is brought to synchronous speed by cutting out the rheostat R2 and

then by cutting in the rheostat R1, if necessary.

4. By gradually cutting out the rheostat R3, the readings of ammeter (A1, 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 R3 is brought to its initial position (cut-in) and TPST (S2) is closed.

2. By gradually cutting out the rheostat R3, reading of the ammeter (A2,0-10/20A) is

adjusted to the rated current of the alternator and the corresponding field current

(A1, 0-1/2A) is noted down.

3. All the rheostats are brought back to their respective initial positions, TPST switch

(S2) and supply switch (S1) are opened.


3. ZPF Test

Sl. No.

I1 Ampere

If Ampere

W1 Watt

W2 Watt

V Volt



b. ZPF Test

1. Connections are made as shown in the circuit diagram (1.b)

2. Keeping the rheostat R1 in the field circuit of the motor in cut-out position, the

rheostat R2 in the armature circuit of the motor and the rheostat R3 in the field

circuit of the generator in cut-in position, the supply switch (S1) is closed.

3. The motor is brought to its rated speed by cutting out the rheostat R2 and

Cutting in the rheostat R1, if necessary.

4. The alternator voltage is built up to its rated value by gradually cutting out the

rheostat R3.

5. The TPST (S2) 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 (S2) is opened and all

Rheostats are brought back to their respective initial positions then the supply

switch (S1) 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 If 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

(IXL) due to armature leakage reactance.


Model Graph

d. Determination of No-Load EMF (Eo)

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 Eo.

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 Eo volts,

Therefore

Regulation %R= 100*

VVEo

where V = voltage / phase, volt

e. Determination of Resultant Field Current (Ifr)

1. BF is measured, which gives field current If1, ampere. 2. DF is measured, which gives Reactive drop IXL, volt. 3. Considering lagging power factor,

E = √ ((V cosФ)2 + (V sinФ + IXL)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 If2.



Therefore resultant field current is given by Ifr = √ (If2

2 + If12 +2 If1 If2cosӨ) Ampere.

CALCULATION:

Signature of Staff-incharge


CIRCUIT DIAGRAM:




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:

Sl. No Particulars. Range Type Quantity

01. Voltmeter 0-300V 0-30V

MI MI

01 01

02 Ammeter. 0-2A 0-10/20A

MI MI

01 01

03. Wattmeter. 2A,300V LPF 01

10/20A,75V UPF 01 PROCEDURE: 1. OPEN CIRCUIT TEST

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 (S1) 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 (S1) 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 (S1) 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 : I1 = (kVA * 1000) / Rated Primary voltage (V1).

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 (S1) is opened.


TABULAR COLUMN:

1. OPEN CIRCUIT TEST

Sl. No VO (Volts) IO (Amps) WO (Watt)


Sl. No VSC (Volts) ISC (Amps) Wsc (Watt)

NOTE:1) Wo = (k1 × Watt Meter Reading.) Where, k1 = Deflection Scale Full

) CosI(V selsel

Wsc = (k2 × Watt Meter Reading.) Where, k2 = Deflection Scale Full

) CosI(V selsel

EQUIVALENT CIRCUIT:



CALCULATION:

1. FROM OPEN CIRCUIT TEST: WO = Iron Loss of Transformer I’

2 = KI2

V’2 = V2 / K i.e.,WO = VoIoCosФo

Therefore CosØ0 =

00

0

IVW

(Exciting Circuit Components): Magnetizing Component of Current; Im = Io SinФo Working Component of Current; Iw = Io CosФo

Exciting Resistance; R0 = I

V

w

0 Ω

Exciting Reactance; X0 = I

V

m

0 Ω

2. FROM SHORT CIRCUIT TEST:

WSC = Full Load Copper Loss of the Transformer Equivalent Resistance Referred to Primary side:

R01 = 2SC

SC

IW

Ω

Equivalent Impedance Referred to Primary side:

Z01 = SC

SC

IV

Ω

Equivalent Reactance Referred to Primary side:

X01 = 201

201 RZ Ω

MODEL GRAPH:



Efficiency of the Transformer:

%ŋ =

)WxW()1000Cos X(S

1000Cos XS

SC2

0

100 [ie ŋ %=

Losses TotalO/PO/P

]

Where: S-Rating of the transformer in KVA.

X- Loads (1, ¾, ½, ¼)

Sl. No.

Load (X) pf %ŋ

1. ¼

1

2. ½

3. ¾

4. 1

1. ¼

0.8

2. ½

3. ¾

4. 1 Regulation of the Transformer:

% Voltage Regulation =

0

0101

VSinØIXCosØIR

100

Where: I- Rated current of the transformer.

+ For lagging power factor & - For leading power factor.

Sl. No. Pf %Regulation

Lagging Leading 1. Unity

2. 0.8

3. 0.6

4. 0.4

5. 0.2

Calculation……….. Signature of Staff-incharge


CIRCUIT DIAGRAM:

Tabular Column

Sl. No

Vmax (V)

Vmin (V)

Imax (A)

Imin (A)

Xd (Ω)

Xq (Ω)

%Regulation

0.8 lag 0.8 lead

Vector Diagram




SLIP TEST ON ALTERNATOR

Aim To determine Xd and Xq of a salient pole alternator by conducting slip test and to

Predetermine its regulation.

Apparatus Required

Procedure


2. Keeping the rheostat R1 in the field circuit of motor in cut-out position, the rheostat

R2 in the armature circuit of motor in cut-in positions, the switch S2 in open position

And 3-phase auto-transformer at zero output position, supply switch (S1) is closed.

3. The motor is brought to a speed slightly less than the synchronous speed of

Alternator by gradually cutting out the rheostat R2 and cutting in the rheostat R1, if

Necessary.

4. A low voltage (say 30-50 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 -----------------------------------Vmax, Volt

Minimum value of voltage------------------------------------Vmin, Volt

Maximum value of current -----------------------------------Imax, Ampere

Minimum value of current------------------------------------Imin, 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 (S1) is opened.

Sl.No Particulars Range Type Quantity

01 Voltmeters 0 – 60 V 0 – 30V

MI MC

01 01

02 Ammeters 0-1/2A 0-2A

MC MI

01 01

03 Rheostats 0-750Ω,1.2 A 0-38Ω,8.5A - 01

01

04 3 phase Auto-transformer - - 01

05 Tachometer - - 01


Determination of Stator Resistance of Alternator (Ra)

Sl. No

V (Volts)

I (Ampere)

Resistance RDC = V/I Ω

Resistance RAC =1.5 × RDC



Determination of Stator Resistance (Ra)

a. Connections are made as shown in the circuit diagram (3.b).

b. By keeping rheostat in cut-in position the supply switch (S1) is closed.

Rheostat is adjusted to any value of current (say 1A)

c. All the meter readings are noted down.

d. The supply switch (S1) is opened.

NOTE: Field of the alternator is kept opened.

Calculation V =Rated phase Voltage, Volt

I = Rated current, Ampere.

Xd= Vmax / Imin =…………… Ω Xq = Vmin / Imax =…………… Ω For 0.8 p.f lagging CosФ = 0.8 SinФ = 0.6 Therefore Ф = 36.86 tanθ = ( V Sin Ф ± I Xq ) / (V Cos Ф + I Ra) ( Note: + → lag , - → lead) θ = tan-1 ((V Sin Ф ± I Xq ) / (V Cos Ф + I Ra)) Therefore α =θ - Ф Therefore Eo/phase = (V Cos α ± Id .Xd + Iq Ra) Volt Where Iq= I Cos θ

Id = I Sin θ

Therefore

Regulation %R= 100*

VVEo



CIRCUIT DIAGRAM:

TABULAR COLUMN:

1. BALANCED LOAD CONDITION

Sl. No.

A1 (Amps)

A2 (Amps)

A3 (Amps)

A4 (Amps)

A5 (Amps)

V (Volts)

I1(TEASER)

(Amps) I1(MAIN)

(Amps)

2. UNBALANCED LOAD CONDITION

Sl. No.

A1 (Amps)

A2 (Amps)

A3 (Amps)

A4 (Amps)

A5 (Amps)

V (Volts)

I1(TEASER) (Amps)

I1(MAIN) (Amps)




SCOTT CONNECTION

AIM:

To verify the currents in the main Transformer and teaser transformer in Scott

connection with balanced and unbalanced load.

APPARATUS REQUIRED:


01. Voltmeter 0-600V MI 01

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 (S1) 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 (S1) is opened.

Calculation:

I1T = 1.15 K I2T Amps where; K = transformation ration of transformer

I1M = K I2M Amps I2T = Secondary teaser transformer current

I2M = Secondary main transformer current

I1T = Primary teaser transformer current

I1M = Primary main transformer current.



CIRCUIT DIAGRAM:




SEPARATION OF HYSTERESIS AND EDDY CURRENT LOSSES IN SINGLE PHASE

TRANSFORMER.

AIM:

To separation the Eddy current loss and Hysteresis loss from the iron loss of 1-Φ

transformer.

APPARATUS REQUIRED:


01. Voltmeter 0-300V MI 01

02. Ammeter 0-10A MI 02

02. Ammeter 0-2A MC 02

03 Rheostats 0-400Ω,1.7A 0-150Ω,2A - 02

01 04 Tachometer - Digital 01

05. Wattmeter 10A,600V LPF 01 PROCEDURE:


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.


TABULAR COLUMN

MODEL GRAPH

Calculation:

1. Frequency(f)=PNs/120

Where P-number of poles; Ns-Synchronous speed in rpm

2. Hysteresis loss(Wh)=A f

3. Eddy current loss(We)=B f2

4. Iron loss or core loss(Wi)= We +Wh

Sl. No.

Speed of Prime Mover (N) rpm

Supply Frequency (f) Hz

Primary Voltage (V) Volts

Wattmeter Reading

(Wi) Watts Wi / f


CIRCUIT DIAGRAM: Resistive Load



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:

Procedure

A. NO- LOAD CHARACTERISTICS

1. Connections are made as shown in the circuit diagram (6.a). 2. Keeping the rheostat R1 in the field circuit of the motor in cut-out position, the

rheostat R2 in the armature circuit of the motor and the rheostat R3 in the field circuit of the generator in cut-in positions, and all load switches in off condition, the supply switch (S1) is closed, the motors starts rotating.

3. The motor is brought to its rated speed by gradually cutting out rheostat R2completelyand cutting in the rheostat R1, if necessary.

4. The generator voltage is built in steps up to its rated value by gradually cutting-out rheostat R3.

5. 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 R1 in the field circuit of the motor in cut-out position, the

rheostat R2 in the armature circuit of the motor and the rheostat R3 in the field circuit of the generator in cut-in positions, and all load switches in off condition, the supply switch (S1) is closed, the motors starts rotating.

3. The motor is brought to its rated speed by gradually cutting out rheostat R2 completely and cutting in the rheostat R1, if necessary.

4. The generator voltage is built up to its rated value by gradually cutting-out rheostat R3.

Sl. No. Particulars Range Type Quantity

01 Voltmeters 0-300V 0-30V

MC MC

01 01

02 Ammeters 0-10/20 A 0-1/2A

MC MC

01 01

03 Rheostats 0-750Ω,1.2A 0-38Ω, 8.5A

- -

02 01



Circuit Diagram (6.b) Circuit Diagram (6.c)

Determination of Armature Resistance (Ra) Determination of Shunt Field Resistance (Rsh) Model Graph



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 R1 and at each step the corresponding values of the terminal voltage (VL), the load current (IL) and the field current (If) 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 (S1) is opened.

Determination of Armature Resistance (Ra) 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 (S1) 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 (S1) is opened.

Determination of Shunt field Resistance (Rsh) 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 (S1) 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 (S1) is opened. Characteristics Curves a. External Characteristics

A graph of VL v/s IL 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 Ia)



TABULAR COLUMN

1. NO-LOAD CHARACTERISTICS

Sl. No.

EO (Volt)

If (Ampere)

2. LOAD CHARACTERISTICS

Sl. No

VL (Volt)

IL (Ampere)

If (Ampere)

Ia = IL+If (Ampere)

Eg=V+IaRa (Volts)

Speed (rpm)

Determination of Armature Resistance (Ra)

Sl. No

V (Volts)

I (Ampere)

Resistance Ra = V/I Ω

Determination of Shunt Resistance (Rsh)

Sl. No

V (Volts)

I (Ampere)

Resistance Rsh = V/I Ω



10. Armature Voltage Drop : Ia Ra = DE

11. Therefore EMF generated after allowing for the drop due to armature reaction: Eg = V + Ia Ra 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: Ia = IL + Ish Amps

EMF Generated : Eg=V + Ia Ra Volts

A graph of Eg v/s Ia is drawn, which represents ‘Internal characteristics’.

Calculation:



CIRCUIT DIAGRAM:

TABULAR COLUMN:

Sl. No V (Volts)

V1 (Volts)

Sl. No V (Volts)

V1 (Volts)




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:



MI MI

01 01

PROCEDURE:


2. The supply switch (S1) is closed.

3. The voltmeter readings are noted.

4. The supply switch (S1) is opened.

5. The same procedure is repeated for circuit diagram (7.b).

6. Observe voltmeter (V1) readings in both the cases.



CIRCUIT DIAGRAM:




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:


01.

02. 03.

Voltmeter

Ammeter Wattmeter

0-300V 0-600V 10/20A

10/20A,500V

MI MI MI UPF

01 01 04 04

PROCEDURE

A) Polarity test:


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:


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 auto-

transformer to its initial zero out-put position, the supply switch is opened.



C) Delta –Delta connection.





transformer (230V).

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

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).




transformer (230V).

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

auto-transformer to its initial zero out-put position, the supply switch is

opened.



TABULAR COLUMN:

A. FOR STAR – DELTA CONNECTION

B. FOR DELTA – DELTA CONNECTION

C. FOR OPEN DELTA (V-V) CONNECTION

Sl.No V (Volts)

V1 (Volts)

Sl.No V1 (Volts)

I1 (Amps)

I2 (Amps)

I3 (Amps)

I4 (Amps)

W1 (Watt)

W2 (Watt)

W3 (Watt)

W4 (Watt)

V2 (Volts)

Sl.No V1 (Volts)

I1 (Amps)

I2 (Amps)

I3 (Amps)

I4 (Amps)

W1 (Watt)

W2 (Watt)

W3 (Watt)

W4 (Watt)

V2 (Volts)

Sl.No V1 (Volts)

I1 (Amps)

I2 (Amps)

I3 (Amps)

I4 (Amps)

W1 (Watt)

W2

(Watt) W3

(Watt) W4

(Watt) V2

(Volts)



Calculation:

NOTE: 1)W1 = (k1 × Watt Meter Reading.) Where, k1= Deflection Scale Full) CosI(V selsel

W2 = (k1 × Watt Meter Reading.) Where, k2= Deflection Scale Full

) CosI(V selsel

W3 = (k3 × Watt Meter Reading.) Where, k3 = Deflection Scale Full

) CosI(V selsel


) CosI(V selsel

% ŋ = 퐖ퟑ + 퐖ퟒ

퐖ퟏ + 퐖ퟐ× ퟏퟎퟎ

%푽풐풍풕풂품풆 풓풆품풖풍풂풕풊풐풏 = 푽ퟐ 풏풐 풍풐풂풅 − 푽ퟐ 풇풖풍풍 풍풐풂풅

푽ퟐ 풇풖풍풍 풍풐풂풅



CIRCUIT DIAGRAM:




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:



MI MI

01 01

02. Ammeter 0-2A 0-10/20A

MI MI

01 01

03 Wattmeter 2A,300V LPF 01

10/20A,75V UPF 01 NOTE: Use 2 similar rating transformers. PROCEDURE:


2. By keeping the 1-Ф auto-transformers (1) and (2) in zero out-put positions, SPST switch (S3) and DPST switch (S2) in open positions, the supply switch (S1) 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 (V2) connected across the SPST switch (S3) 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 (S1) and interchange one of the transformer’s secondary terminals.

5. Close the supply switch (S1), repeat step no-3. Close SPST switch (S3). (By

ensuring voltmeter (V2) reads zero). The watt-meter (W0), voltmeter (V1) and ammeter (I1) readings are noted down.

6. Switch (S2) 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 (WCU) and ammeter (I2) readings are noted down.

7. The auto-transformers (2) and then (1) are brought back to their initial zero out-

put positions, the DPST switch (S2), SPST switch (S3), and supply switch (S1) are opened.


TABULAR COLUMN:

NOTE:1) Wo = (k1 × Watt Meter Reading.) Where, k1 = Deflection Scale Full

) CosI(V selsel

Wcu = (k2 × Watt Meter Reading.)

Where, k2 = Deflection Scale Full

) CosI(V selsel

MODEL GRAPH:

Calculation……

Rated current of Transformer = Voltage Rated

1000kVA x

Total Iron loss in both transformers = Wi = _______ Watt

Iron loss in each transformer = Wi/2 = 2

Wi = ________ Watt

Full load total Copper loss of both transformers = Wcu=__________ Watt

Sl. No V1 (Volts)

I1 (Amps)

Wo (Watt)

I2 (Amps)

Wcu (Watt)



Full load Copper loss of each transformer = WCU/2 = 2Wcu =__________ Watt

a. For combined efficiency (ŋ)

%ŋ= 100 WxWi1000 cosXS

1000 cosXS

cu2

[ie ŋ %=

Losses TotalO/PO/P

]

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)

%ŋ= 100 WxW1000 cosXS

1000 cosXS

cu/22

i/2

[i.e., ŋ%=

Losses TotalO/PO/P

]

Combined efficiency (ŋ) Individual efficiency (ŋ)


Sl. No x (Load) pf % ŋ

01. 1

UPF

02. ¾

03. ½

04. ¼

05. 1

0.7

06. ¾

07. ½

08. ¼

Sl. No x (Load) pf % ŋ

01. 1

UPF

02. ¾

03. ½

04. ¼

05. 1

0.7

06. ¾

07. ½

08. ¼


CIRCUIT DIAGRAM:


Dept. of EEE, C.I.T, Gubbi, 572 216 Page No.42


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

Sl. No. Particulars Range Type Quantity

01 Voltmeter 0 – 600 V MI 01

02 Ammeters 0-1/2A 0-5/10A

MC MI

01 01

03 Rheostats 0-750Ω,1.2A 0-38Ω,8.5A

- -

02 01

04 Watt meters 10/20A, 0 – 600 V LPF 02

05 Tachometer - - 01 Procedure a. Operation on Infinite Bus Bar


2. Keeping the rheostat R1 in the field circuit of motor in cut-out position, the rheostat R2 in the armature circuit of motor and the rheostat R3 in the field circuit of alternator in cut-in positions, the bus bar switch (S2)and synchronizing switch (S3) in open positions, the supply switch (S1) is closed.

3. The motor is brought to the synchronous speed of the alternator by gradually cutting out the rheostat R2 and cutting in the rheostat R1, if necessary.

By gradually cutting out the rheostat R3, the alternator voltage is built-up to the bus bar voltage.

4. Now, bus bar switch (S2)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 4.

6. By varying the rheostats R1, R2 and R3 the dark period of the lamps are obtained.

7. When all the lamps are in dark condition, the synchronization switch S3 is closed and now the alternator is connected in parallel with the bus bar.

8. Switches (S3) and (S2) are opened; all the rheostats are brought back to their respective initial positions, and supply switch (S1) is opened.



b. Constant Power - Variable Excitation Operation


2. Follow the procedure steps 2, 3 of procedure (a)

3. By gradually cutting out the rheostat R3, 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 (S1)is

opened.

c. Constant Excitation - Variable Power Operation


2. Follow the procedure steps 2, 3 of procedure (a).


rated voltage.

4. Apply load in steps & note down all meter readings (Excitation should be constant

by adjusting the speed of the Motor).


rheostats are brought back to respective initial positions & supply switch (S1) is

opened.



Tabular Column 1. Constant Power - Variable Excitation Operation

Sl. No.

If (A)

Power (W1+W2)

Speed (RPM)

Voltage (V)

IL (A)

2. Constant Excitation - Variable Power Operation

Sl. No.

If (A)

Power (W1+W2)

Speed (RPM)

Voltage (V)

IL (A)



Calculation:



CIRCUIT DIAGRAM:




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



MC MI

01 01

02 Ammeters 0-10/20A 0-1/2A

MI MC

01 01

03 Rheostats 0-750Ω,1.2A 0-38Ω,8.5A - 02

01



1. Connections are made as shown in the circuit diagram (11.a) 2. Keeping the rheostat R1 in the field circuit of motor in cut-out position, the rheostat

R2 in the armature circuit of the motor and the rheostat R3 in field circuit of the alternator in cut-in positions and TPST (S2) in open position, the supply switch (S1) is closed.

3. The motor is brought to synchronous speed by cutting out the rheostat R2 and then by cutting in the rheostat R1, if necessary.

4. By gradually cutting out the rheostat R3, the readings of ammeter (A1, 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 R3 is brought to its initial position (cut-in) and TPST (S2) is closed. 2. By gradually cutting out the rheostat R3, reading of the ammeter (A2, 0-10/20A) is

adjusted to the rated current of the alternator and the corresponding field current (A1) is noted down.

3. All the rheostats are brought back to their respective initial positions, TPST switch (S2) and supply switch (S1) are opened.


Tabular Column 1. Open Circuit Test 2. Short Circuit Test

Sl.No If Amps V0 Volts

VL Vph

Sl.No If Amps IscAmps



Determination of Armature Resistance (Ra) by V-I Method


2. Keeping the rheostat in cut-in position, the supply switch (S1) is closed, Rheostat is

adjusted to any value of current (say 1A) and the readings of ammeter and

voltmeter are noted down.


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, E1 is the open circuit voltage per phase, and BC is the Short circuit current. Therefore Synchronous impedance per phase Zs = E1/I1Ω (If Constant) Synchronous reactance per phase Xs = √ Zs

2- Ra2 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 = √OA2 + AB2 i.e. E = √((V cosФ+ IRa)2 + (V sinФ + IXs)2) Volt.

Therefore %R= 100*

VVE

(b) Regulation for leading power factor: From the vector diagram, as shown in fig.(3)

OB = √OA2 + AB2 i.e. E = √((V cosФ+ IRa)2 + (V sinФ - IXs)2 )Volt.

Therefore %R= 100*

VVE

.

(c) Regulation for Unity power factor: From the vector diagram, as shown in fig.(1) E = √((V + IRa)2 + IXs

2 )Volt.

Therefore %R= 100*

VVE



Determination of Stator Resistance of Alternator (Ra) % Regulation Tabular Column

PF 0.2 0.4 0.6 0.8 1.0 REMARKS

LEAD

FOR E.M.F

METHOD LAG

LEAD

FOR M.M.F

METHOD LAG

Sl.No V (Volts)

I (Ampere)


Resistance RAC =1.5*RDC



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, Isc, 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 Et )

Therefore %R= 100*

VVE

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.)


Model Graphs 1. EMF Method

Graph No. 1

2. MMF Method

Graph No. 2 Graph No. 3


Vector Diagrams I. EMF METHOD 1. UNITY POWER FACTOR 2. LAGGING POWER FACTOR

3. LEADING POWER FACTOR II. MMF METHOD

Regulation Curve

CALCULATION:



CIRCUIT DIAGRAM:




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:



MI MI

01 01

02. Ammeter 0-5 0-20A

MI MI

01 02

03. Wattmeter

20A,300V UPF 01

10/20A,75V UPF 01

5A,300V UPF 01

PROCEDURE: 1) PARELLEL OPERATION

1. Circuit connections are made as shown in the circuit diagram (12.a).

2. Keeping the load switch (S2) and SPST switch (S3) in open position, the supply

switch (S1) 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 (S3) 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 (S1)

is opened.

5. The secondary connections of any one of the transformers is interchanged and

close the supply switch (S1).

6. Now close the SPST switch (S3). (Ensuring voltmeter V2 reads zero voltage)

7. The load switch (S2) 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 (S3) and load switch (S2) are

opened.

9. Gradually reduce the auto transformer voltage to zero then supply switch (s1) is

opened.


TABULAR COLUMN:

1. PARELLEL OPERATION


Transformer Isc Wsc Vsc Remarks

1. 2 KVA

2. 1 KVA

NOTE: 1)W1 = (k1 × Watt Meter Reading.) Where, k1= Deflection Scale Full) CosI(V selsel

W2 = (k1 × Watt Meter Reading.) Where, k2= Deflection Scale Full) CosI(V selsel


) CosI(V selsel

Wsc = (k4 × Watt Meter Reading.) Where, ksc = Deflection Scale Full

) CosI(V selsel

Sl. No

W1 (Watt)

W2 (Watt)

W3 (Watt)

I1 (Amps)

I2 (Amps) I3

(Amps) Actual Theoretical Actual Theoretical



2) SHORT CIRCUIT TEST


2. Keeping 1-Ф auto-transformer voltage in zero out-put position, the supply switch

(S1) 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 (S1) is opened.

6. The above steps are repeated for another transformer.

CALCULATION:

1. For Transformer I (4 KVA)

Z01 = SC

SC

IV

Ω = R01 = 2SC

SC

IW

Ω = X01= 21

21 RZ Ω=

2. For Transformer II (1 KVA)

Z02 = SC

SC

IV

Ω = R02 = 2SC

SC

IW

Ω = X02 = 22

22 RZ Ω=

THEORETICAL CALCULATION:

I1 = 0201

023

ZZZI

=

2

02012

0201

202

2023

XXRR

XRI

Amps

I2 = 0201

013

ZZZI

=

2

02012

0201

201

2013

XXRR

XRI

Amps

Calculation………..



CIRCUIT DIAGRAM:

Tabular Column 1. Open Circuit Test 2. Short Circuit Test

Sl.No If Amps V0 Volts

VL Vph

Sl. No If Amps IscAmps




POWER ANGLE CURVE OF SYNCHRONOUS GENERATOR

Aim To study the power angle curve of Synchronous Generator.

Apparatus Required



MC MI

01 01

02 Ammeters 0-10/20A 0-1/2A

MI MC

01 01

03 Rheostats 0-750Ω,1.2A 0-38Ω,8.5A - 02

01



1. Connections are made as shown in the circuit diagram (13.a) 2. Keeping the rheostat R1 in the field circuit of motor in cut-out position, the

rheostat R2 in the armature circuit of the motor and the rheostat R3 in field circuit of the alternator in cut-in positions and TPST (S2) in open position, the supply switch (S1) is closed.

3. The motor is brought to synchronous speed by cutting out the rheostat R2 and then by cutting in the rheostat R1, if necessary.

4. By gradually cutting out the rheostat R3, the readings of ammeter (A1, 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 R3 is brought to its initial position (cut-in) and TPST (S2) is closed. 7. By gradually cutting out the rheostat R3, reading of the ammeter (A2, 0-10/20A) is

adjusted to the rated current of the alternator and the corresponding field current (A1) is noted down.

8. All the rheostats are brought back to their respective initial positions, TPST switch (S2) and supply switch (S1) are opened.


Determination of Stator Resistance of Alternator (Ra)

Sl.No V (Volts)

I (Ampere)


Resistance RAC =1.5*RDC


Determination of Armature Resistance (Ra) by V-I Method


10. Keeping the rheostat in cut-in position, the supply switch (S1) is closed, Rheostat

is adjusted to any value of current (say 1A) and the readings of ammeter and

voltmeter are noted down.


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).


rated voltage.

4. Apply load in steps & note down all meter readings (Excitation should be constant

by adjusting the speed of the Motor).


rheostats are brought back to respective initial positions & supply switch (S1) 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, E1 is the open circuit voltage per phase, and BC is the Short circuit current. Therefore Synchronous impedance per phase Zs = E1/I1Ω (If Constant) Synchronous reactance per phase Xs = √ Zs

2- Ra2 Ω

Model Graph:

Graph No. 1


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 = 90o. Beyond this point the machine falls out of step

and loses synchronism. The machine can be taken up to Pi 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 90o.


Calculations

Ra = ________ Ohm

Zs = ________ Ohm

Xs = ________ Ohm

P = W1 + W2 Watts

E = V + j IZs

E = √ V2 + (IZS)2

Where E = Generator internal emf

V = Terminal voltage

δ = Load angle i. e angle between the E and V.

XS = Synchronous Reactance




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 VSp.f curve.

4. Draw the equivalent circuit of the given single phase transformer by conducting necessary tests.

5. Draw the %η VS 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 VS 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.



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, pre-determine 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!!!!!!



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?



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?



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.

8. www.bhel.com

9. www.ijems-world.com

10. www.ieeexplore.ieee.org



Appendix

STUDY OF ELECTRICAL SYMBOLS

Sl. No. Particulars Symbol

1 Electrical wire

_______

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



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



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



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


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

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