ELECTRICAL MACHINES-II
LABORATORY MANUAL
BY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS
ENGINEERING
DHULLAPALLY, KOMPALLY
SECUNDERABAD-500014
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
INDEX
List of experiments as per university
3
List of experiments to be conducted for this semester
4
Cycle indicate schedule and the batch size
5
Laboratory Practice Safety Rules Guidelines For Laboratory
Notebook
6
S.NO
1
NAME OF THE EXPERIMENT
O.C. &S.C. Tests on single phase transformer.
PG.NO
10-13
2
Sumpner's test on a pair of single phase transformers.
13-17
3
Brake test on three phase squirrel cage induction motor.
18-20
4
No-load& blocked rotor tests on three phase Slip ring Induction
motor.
21-24
5
Regulation of a three phase alternator by synchronous
impedance (EMF&MMF) method.
25-28
6
V and inverted V curves of a three –phase Synchronous motor.
29-31
7
Equivalent circuit of a single phase induction motor.
32-35
8
Determination of Xd and Xq of a salient pole synchronous
machine.
36-39
9
ADDITIONAL EXPERIMENTS
Parallel Operation of Single Phase Transformers.
40-43
10
Separation of core losses of a single phase transformer.
43-47
11
Scott connection of Transformers.
48-50
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY
III Year B.Tech EEE I Sem
Academic year 20142015L T/P/D C
0 -/3/-2
(55602) ELECTRICAL MACHINES LAB–II
The following experiments are required to be conducted as compulsory experiments.
1. O.C. &S.C. Tests on single phase transformer.
2. Sumpner's test on a pair of single phase transformers.
3. Brake test on three phase squirrel cage induction motor.
4. No-load& blocked rotor tests on three phase Slip ring Induction motor.
5. Regulation of a three phase alternator by synchronous impedance (EMF&MMF) method.
6. V and inverted V curves of a three –phase Synchronous motor.
7. Equivalent circuit of a single phase induction motor.
8. Determination of Xd and Xq of a salient pole synchronous machine.
In addition to the above experiments, at least any two of the experiments from the
following list are required to be conducted.
1. Parallel Operation of Single Phase Transformers.
2. Separation of core losses of a single phase transformer.
3. Scott connection of Transformers.
4. Regulation of a three phase alternator by ZPF&ASA method.
5. Efficiency of a three phase alternator.
6. Heat run test on a bank of 3Nosof single phase delta connected transformers.
7. Measurement of sequence Impedance ofa3phase alternator.
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ELECTRICAL MACHINES-II LAB MANUAL
Experiments Conducted by the Department:1. O.C. &S.C. Tests on single phase transformer.
2. Sumpner's test on a pair of single phase transformers.
3. No-load& Blocked rotor tests on three phase induction motor.
4. Separation of core losses of a single phase transformer.
5. Efficiency of a three phase alternator.
6. Brake test on three phase induction motor.
7. Regulation of a three phase alternator by synchronous impedance & m.m.f methods
8. V and inverted V curves of at here phase synchronous motor.
9. Equivalent circuit of a single phase induction motor.
10. Determination of Xd and Xq of a Salient pole synchronous machine.
Additional Experiments
1. Parallel Operation of Two Single Phase Transformers.
2. Measurement of sequence Impedance ofa3phase alternator.
3. Scott connection of Transformers.
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ELECTRICAL MACHINES-II LAB MANUAL
FIRSTCYCLEEXPERIMENTS:
EXP NO
EXPERIMENT NAME
1
O.C. &S.C. Tests on single phase transformer.
2
Sumpner's test on a pair of single phase transformers.
3
Brake test on three phase squirrel cage induction motor.
4
No-load& blocked rotor tests on three phase Slip ring Induction motor.
5
Regulation of a three phase alternator by synchronous impedance
(EMF&MMF) method.
SECOND CYCLEEXPERIMENTS:
EXP NO
EXPERIMENT NAME
6
V and inverted V curves of a three –phase Synchronous motor.
7
Equivalent circuit of a single phase induction motor.
8
Determination of Xd and Xq of a salient pole synchronous machine.
9
Parallel Operation of Single Phase Transformers.
10
Separation of core losses of a single phase transformer.
11
Scott connection of Transformers.
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ELECTRICAL MACHINES-II LAB MANUAL
LABORATORY PRACTICE SAFETY RULES
SAFETY is of paramount importance in the Electrical Engineering Laboratories.
1. Electricity NEVEREXECUSES careless persons. So, exercise enough care and attention in
handling electrical equipment and follow safety practices in the laboratory.(Electricity is a
good servant but a bad master).
2.Avoid direct contact with any voltage source and power line voltages.(Otherwise, any such
contact may subject you to electrical shock)
3.Wear rubber-soled shoes. (To insulate you from earth so that even if you accidentally
contact a live point, current will not flow through your body to earth and hence you will be
protected from electrical shock)
4.Wear laboratory-coat and avoid loose clothing.(Loose clothing may get caught on an
equipment/instrument and this may lead to an accident particularly if the equipment
happens to be a rotating machine)
5.Girl students should have their hair tucked under their coat or have it in a knot.
6.Do not wear any metallic rings, bangles, bracelets, wristwatches and neck chains. (When
you move your hand/body, such conducting items may create short circuit or may ouch a
live point and there by subject you to electrical shock)
7.Be certain that your hands are dry and that you are not standing on wet floor. (Wet parts of
the body reduce the contact resistance there by increasing the severity of the shock)
8.Ensure that the power is OFF before you start connecting up the circuit.(Otherwise you will
be touching the live parts in the circuit)
9. Get your circuit diagram approved by the staff member and connect up the circuit strictly
as per the approved circuit diagram.
11. Check power chords for any sign of damage and be certain that the chords use safety
plugs and do not defeat the safety feature of these plugs by using ungrounded plugs.
12. When using connection leads, check for any insulation damage in the leads and avoid
such defective leads.
13.Do not defeat any safety devices such as fuse or circuit breaker by shorting across it.
Safety devices protect YOU and your equipment.
14.Switch on the power to your circuit and equipment only after getting them checked up
and approved by the staff member.
15.Take the measurement with one hand in your pocket. (To avoid shock in case you
accidentally touch two points at different potentials with your two hands)
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ELECTRICAL MACHINES-II LAB MANUAL
16.Do not make any change in the connection without the approval of the
staffmember.17.Incaseyou notice any abnormal condition in your circuit (like
insulation heating up,
Resistor heating up etc ), switch off the power to your circuit immediately and inform the
staff member.
18.Keep hot soldering iron in the holder when not in use.
19.After completing the experiment show your readings to the staff member and switch off
the power to your circuit after getting approval from the staff member.
20.While performing load-tests in the Electrical Machines Laboratory using the brake-drums:
Avoid the brake-drum from getting too hot by putting just enough water into the brakedrum at intervals; use the plastic bottle with a nozzle (available in the laboratory)to pour the
water.(When the drum gets too hot, it will burn out the braking belts)
Do not stand in front of the brake-drum when the supply to the load-test circuit is switched
off.(Otherwise, the hot water in the brake-drum will splash out on you)
After completing the load-test, suck out the water in the brake-drum using the plastic bottle
with nozzle and then dry off the drum with a sponge which is available in the
of data in a concise visual form. Data to be presented in graphical form should be plotted
in the laboratory so that any questionable data points can be checked while the experiment is
still set up. The gridlines in the note book can be used for most graphs. If special graph
paper is required, affix the graph permanently into the notebook. Give all graphs a short
descriptive title. Label and scale the axes. Use units of measure. Label each curve if more
than one on a graph.
21. Determine the correct rating of the fuse/s to be connected in the circuit after
Understanding correctly the type of the experiment to be performed: no-load test or fullload test, the maximum current expected in the circuit and accordingly use that fuserating.(While an over-rated fuse will damage the equipment and other instruments like
ammeters and watt-meters in case of over load, an under-rated fuse may not allow one even
to start the experiment)
22. At the time of starting a motor, the ammeter connected in the armature circuit over shoots,
as the starting current is around 5 times the full load rating of the motor. Moving coil
ammeters being very delicate, may get damaged due to high starting current. A switch has
been provided on such meters to disconnect the moving coil of the meter during starting.
This switch should be closed after the motor attains full speed. Moving iron ammeters and
current coils of watt meters are not so delicate and hence these can stand short time
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ELECTRICAL MACHINES-II LAB MANUAL
overload due to high starting current. No such switch is therefore provided on these meters.
Moving iron meters are cheaper and more rugged compared to moving coil meters. Moving
iron meters can be used for both a.c. and d.c. measurement. Moving coil instruments are
however more sensitive and more accurate as compared to their moving
iron counter parts and these can be used for d.c. measurements only. Good features of
moving coil instruments are not of much consequence for you as other sources of errors in
the experiments are many times more than those caused by these meters.
23. Some students have been found to damage meters by mis handling in the following ways:
Keeping unnecessary material like books, lab records, un used meters etc. causing meters
to fall down the table.
Putting pressure on the meter (specially glass) while making connections or while talking
or listening somebody.
STUDENTS ARE STRICTLY WARNED THAT FULL COST OF THE METER WILL BE
RECOVERED FROM THE INDIVIDUALWHO HAS DAMAGED IT IN SUCH A
MANNER.
Copy these rules in your Lab Record. Observe these yourself and help your friends to observe I
have read and understand these rules and procedures. I agree to abide by these rules and
procedures at all times while using these facilities. I understand that failure to follow these
rules and procedures will result in my immediate dismissal from the laboratory and additional
disciplinary action may be taken.
GUIDELINESFOR LABORATORY NOTEBOOK
The laboratory notebook is a record of all work pertaining to the experiment. This record
should be sufficiently complete so that you or any one else of similar technical back ground
can duplicate the experiment and data by simply following your laboratory note book. Record
everything directly into the notebook during the experiment. Do not use scratch paper for
recording data. Do not trust your memory to fill in the details at a later time. Organization in
your note book is important. Descriptive headings should be used to separate and identify the
various parts of the experiment. Record data in chronological order. A neat, organized and
complete record of an experiment is just as important as the experimental work.
1. Heading:
The experiment identification (number) should beat the top of each page. Your name
and date should beat the top of the first page of each day's experimental work.
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ELECTRICAL MACHINES-II LAB MANUAL
2. Object:
A brief but complete statement of what you intend to find out or verify in the
experiment should be at the beginning of each experiment
3. Diagram:
A circuit diagram should be drawn and labeled so that the actual experiment circuitry
could be easily duplicated at any time in the future. Be especially careful to record all circuit
changes made during the experiment.
4.Equipment List:
List those items of equipment which have a direct effect on the accuracy of the data. It
may be necessary later to locate specific items of equipment for rechecks if discrepancies
develop in the results.
5. Procedure:
In general, lengthy explanations of procedures are un necessary. Be brief. Short
commentaries along side the corresponding data may be used. Keep in mind the fact that the
experiment must be reproducible from the information given in your notebook.
6. Data:
Think carefully about what data is required and prepare suitable data tables. Record
instrument readings directly. Do not use calculated results in place of direct data; however,
calculated results may be recorded in the same table with the direct data. Data tables should be
clearly identified and each data column labeled and headed by the proper units of measure.
7. Calculations:
Not always necessary but equations and sample calculations are often given to
illustrate the treatment of the experimental data in obtaining the results.
8. Graphs:
Graphs are used to present large amounts of results. Theoretical and experimental
results should be on the same graph or arrange in the same table in a way for easy correlation
of these results.
9.Results:
The results should be presented in a form which makes the interpretation easy. Large
amounts of numerical results are generally presented in graphical form. Tables are generally
used for small amounts laboratory.(The water, if allowed to remain in the brake-drum, will
corrode it)
9. Conclusion:
This is your interpretation of the results of the experiment as an engineer. Be brief
and specific. Give reasons for important discrepancies.
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ELECTRICAL MACHINES-II LAB MANUAL
EXP.NO. 01
1. OC &SCTESTSON 1-Φ TRANSFORMER
AIM:
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:
1Φ- TRANSFORMER
T/F
Rated power
LV side
HV side
Rated voltage
Rated current
Frequency
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MI
2
Ammeter
MI
3
Voltmeter
MI
4
Voltmeter
MI
5
Wattmeter
EDM(LPF)
6
Wattmeter
EDM(UPF)
7
Single phase variac
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Range
Quantity
Page 10
THEORY:Open– Circuit (OC) or No-Load Test:
Thepurposeofthistestistodeterminetheshuntbranchparametersoftheequivalentcircuitofthetransfor
mer.Oneofthewindings 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.Thismeansthatforallpracticalpurposesthepowerinputonnoloadequalsthecore(iron)lossi.e.,
P0=V1 I0 cosf0
cosf0 = P0/V1I0
Iw=I0 cosf0,
m
=I0sinf0
R0=V1/Iw,
X0=V1 / Im
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
Vsc=Voltage, Isc=Current, Psc=Power Copper loss)
Z01= VSC/ ISC=√R201 + X201
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Equivalent resistance, R01=PSC/ (ISC)2
Equivalent reactance, X01= √Z201-R201
CIRCUIT DIAGRAM: DIAGRAM--1
PROCEDURE:
OC TEST:
(1) All the connections are done as per the circuit diagram of OC test
(2) Byusing1-f 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-f 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
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PRECAUTIONS:
(1) Open circuit test is performed on LV side i.e meters are connected LV side and HV side
will be open circuited.
(2) For short circuit test is connect meters on HV side and LV side will be short circuited
(3) Rated voltage and rated current must be maintained in OC test and SC test respectively
(4) All the connections must be tight
TABULAR COLUMNS
Observations:
OC TEST:
Vo
Volts
Io
Amps
Wo
Watts
Isc
Amps
Wsc
Watts
SC TEST:
Vsc
Volts
CALCULATIONS:
EFFICIENCY VS LOAD:
Power factor lagging
LOAD
0.2
0.4
0.6
0.8
1
¼
½
¾
1
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Regulation:
Power factor lagging
LOAD
0.2
0.4
0.6
UPF
0.8
Power factor leading
1
0.8
0.6
0.4
0.2
1/4
1/2
3/4
1
MODEL GRAPHS:
%Regulation
Pflea
Pf lagging
%Regulation
RESULT:
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EXP.NO. 02
SUMPNERS TEST ON SINGLE PHASE TRANSEFORMERS
AIM:
To convert three phase system to two phase system with the help of Scott Connection.
NAMEPLATE DETAILS:
1Φ- TRANSFORMERS
T/F
T/F-1
HV side
LV side
T/F-2
HV side
LV side
Rated power
Rated voltage
Rated current
Frequency
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MI
2
Ammeter
MI
3
Voltmeter
MI
4
Voltmeter
MI
5
Wattmeter
EDM(LPF)
6
Wattmeter
EDM(UPF)
7
Voltmeter
MI
Range
Quantity
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 can not
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 give more accurate results of regulation and
efficiency than O.C. and S.C. tests.
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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 thm aree opposite to each other. Another low voltage
supply is connected in series with secondaries to get of them are connected in voltage
opposition, i.e. EEF and EGH. 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 V1 is 2I0, where I0 is equal to no load current of
each transformer. Thus input power measured by wattmeter W1 is equal to iron losses of both
transformers.
i.e. iron loss per transformer Pi = W1/2.
Now, a small voltage V2 is injected into secondary with the help of a low voltage transformer.
The voltage V2 is adjusted so that, the rated current I2 flows through the secondary. In this case,
both primaries and secondaries carry rated current. Thus short circuit test is simulated and
wattmeter W2 shows total full load copper losses of both transformers.
i.e. copper loss per transformer PCu = W2/2.
From test results, the full load efficiency of each transformer can be given as -
CIRCUIT DIAGRAM: DIAGRAM--2
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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 W1 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 W2 are noted down.
TABULAR COLUMN:
W1
W2
FORMULE:
GRAPH:
h%
RESULT:
IL(Amps)
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EXP.NO. 03
BRAKE TEST ON 3–Φ SQUIRREL CAGE I NDUCTION MOTOR
AIM:
To draw the performance characteristics of 3-phase squirrel cage induction motor by
conducting load test.
NAMEPLATE DETAILS:
Parameters
Induction Motor
Rated Power
Rated Voltage
Rated Current
Rated Speed
APPARATUSREQUIRED:
S. No
Name of apparatus
Type
1.
Ammeter
MI
2.
Voltmeter
MI
Range
Qty.
THEORY:
A 3-phase induction motor consists of stator and rotor with the other associated parts. In the
stator, a3-phase winding is provided. The windings of the three phase are displaced in
spaceby120º. A 3-phasecurrent is fed to the 3-phase winding. These windings produce a
resultant magnetic flux and it rotates in space like a solid magnetic poles being rotated
magnetically.
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CIRCUIT DIAGRAM: DIAGRAM--3
PROCEDURE:
1. Connections are given as per circuit diagram.
2.3-Ф induction motor is started with DOL starter.
3. If the pointer of one of the wattmeter readings reverses, inter change the current coil
terminals and Take the reading as negative.
4. The no load readings are taken.
5. The motor is loaded step by step till we get the rated current and the readings of the
voltmeter, ammeter, wattmeter’s, spring balance are noted.
PRECAUTIONS:
1.TPST switch is kept open initially.
2.There must be no load when starting the load.
FORMULAE USED:
1) %slip= (Ns-N/Ns)*100
2) Input Power =(W1+W2)watts
3) Output Power=2∏NT/60 watts
4) Torque =9.81*(S1-S2)*R N-m
5) %efficiency=(o/p power/i/p power)* 100
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OBSERVATIONS:
S.NO
Line
Voltage
volts
Input
Current
Amps
Wattmeter Reading
W1*4
W2*2
watts
S1
Spring Control
S2
Speed
watts
1
2
3
4
5
6
GRAPHS:
1)
2)
3)
4)
Output Power vs Efficiency
Output Power vs Torque
Output Power vs Speed
Output Power vs %s
RESULT:
Hence the load test on Squirrel cage Induction motor is performed and performance
characteristics are drawn.
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EXP.NO. 04
NO LOAD AND BLOCKED ROTOR TEST ON 3- PHASE INDUCTION MOTOR
AIM:
To conduct the no load &blocked rotor test on 3- phase induction motor & to draw the
equivalent circuit of 3-phase squirrel cage induction motor.
NAMEPLATE DETAILS:
Parameters
Induction Motor
Rated Power
Rated Voltage
Rated Current
Rated Speed
APPARATUSREQUIRED:
S. No
Name of apparatus
Type
1.
Ammeter
MI
2.
Voltmeter
MI
3.
Wattmeter
EDM
4.
Tachometer
digital
5.
Connecting Wires
Range
Qty.
THEORY :
A 3-phase induction motor consists of stator, rotor & other associated parts. In the stator, a 3phase winding (provided) are displaced in spaceby120. A 3- phase current is fed to the
winding so that a resultant rotating magnetic flux is generated. The rotor starts rotating due to
the induction effect produced due the relative velocity between the rotor Winding &the
rotating flux.
As a general rule, conversion of electrical energy to mechanical energy takes place in to the
rotating part on electrical motor. In DC motors, electrical power is conduct directly to the
armature, i.e, rotating part through brushes and commutator. Hence, in this sense, a DC
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motor can be called as 'conduction motor'.
However, in AC motors, rotor does not receive power by conduction but by induction in
exactly the same way as secondary of a two winding T/F receives its power from the
primary. So, these motors are known as Induction motors. In fact an induction motor can be
taken as rotating T/F, i.e, one in which primary winding is stationary and but the secondary
is free.
The starting torque of the Induction motor can be increase by improving its p.f by adding
external resistance in the rotor circuit from the stator connected rheostat, the rheostat
resistance being progressively cut out as the motor gathers speed. Addition of external
resistance increases the rotor impedance and so reduces the rotor current. At first, the effect
of improved
p.f predominates the current decreasing effect of impedance. So, starting torque is
increased. At time of starting, external resistance is kept at maximum resistance position
and after a certain time, the effect of increased impedance predominates the effect of
improved p.f and so the torque starts decreasing. By this during running period the rotor
resistance being progressively cut-out as the motor attains its speed. In this way, it is
possible to get good starting torque as well as good running torque.
CIRCUIT DIAGRAM: DIAGRAM—4
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PROCEDURE:
NO LOAD TEST:
(1).Connections are given as pert he circuit diagram.
(2).Precautions are observed and motor is started on the no load.
(3).Autotransformer is varied to have rated voltage applied.
(4).The meter readings are then tabulated.
BLOCKEDROTOR TEST:
(1).Connections are given as per circuit diagram.
(2).Precautions are observed and motor is started on full load or blocked rotor position.
(3).Autotransformer is varied to have rated current flowing in motor.
(4).The meter readings are then tabulated.
PRECAUTIONS:
NO LOAD TEST:
(1).Initially TPST switch is kept open.
(2).Autotransformer must be kept at minimum potential position.
(3).The machine must be started at no load.
BLOCKEDROTOR TEST:
(1).Initially the TPST switch is kept open.
(2).Autotransformer must be kept at minimum potential position.
(3).The machine should be started on full load.
FORMULAUSED:
FOR NO LOAD TEST:
Wsc =√3 Vo Io COSФ watts
Iw = Io cosФ amps
Ro=V0/Iw Ω
Xo=Vo/Iu Ω
FORBLOCKED ROTOR TEST:
Wsc =3I2*Ro Watts
Ro1 = Wsc/3(Isc)2 Ω
Zo1 =Vsc/Isc Ω
Xo1 =√Zo1^2-Ro1^2 Ω
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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TABULAR COLUMNS:
NO LOAD TEST:
Voltage
Voc
Current
Ioc
Volts
Amps
Wattmete
r readings
(W1)
Wattmeter
readings(W2)
Φo=
Total
cosΦo=
Power
Wo/(3 Voc Ioc)
Wo(W1-W2)
Voc= open circuit voltage
I oc =open circuit current
BLOCKEDROTOR TEST:
Voltage
Vsc
Volts
Current
Isc
Amps
Wattmeter
readings
(W1)
Φsc=
Wattmeter
Total
cosΦ
Wsc/ o=
readings(W2) PowerWsc (√3VscIsc)
(W1-W2)
Vsc=short circuit voltage ,Isc =short circuit current
GRAPH:
RESULT:
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 24
EXP.NO. 05
REGULATION OF3–ΦALTERNATOR BY
SYNCHRONOUS IMPEDANCE AND MMF METHOD
AIM:
To predetermine the regulation of 3-phase alternator by EMF and MMF methods and
Also draw the vector diagrams.
NAMEPLATE DETAILS:
Parameters
DC Shunt Motor
Alternator
Rated Power
Rated Voltage
Rated Current
Rated Speed
Rated field current
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MC
2
Ammeter
MI
4
Voltmeter
MI
5
Rheostat
Wire wound
6
Potential Divider
Wire wound
7
Tachometer
Range
Quantity
Digital
THEORY:
The regulation of a 3-phase alternator may be predetermined by conducting the
Open Circuit (OC) and the Short Circuit (SC) tests. The methods employed for
determination of regulation are EMF or synchronous impedance method, MMF or
Ampere Turns method and the ZPF or Potier triangle method. In this experiment, the
EMF and MMF methods are used. The OC and SC graphs are plotted from the two tests.
The synchronous impedance is found from the OC test. The regulation is then determined
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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at different power factors by calculations using vector diagrams. The EMF method is also
called pessimistic method as the value of regulation obtained is much more than the actual
value. The MMF method is also called optimistic method as the value of regulation
obtained is much less than the actual value. In the MMF method the armature leakage
reactance is treated as an additional armature reaction. In both methods the OC and SC
test data are utilized.
CIRCUIT DIAGRAM: DIAGRAM---5
PROCEDURE: (FORBOTH EMFAND MMFMETHODS)
1.
2.
3.
4.
Note down the name plate details of the motor and alternator.
Connections are made as per the circuit diagram.
Switch ON the supply by closing the DPST switch.
Using the Three point starter, start the motor to run at the synchronous speed
by adjusting the motor field rheostat.
5. ConductOpenCircuittestbyvaryingthepotentialdividerforvariousvaluesoffieldcurrent
andtabulate the corresponding Open Circuit Voltage readings.
6. ConductShortCircuittestbyclosingtheTPSTswitchandadjustthepotentialdividerto set
the rated armature current and tabulate the corresponding field current.
7. TheStatorresistanceperphaseisdeterminedbyconnectinganyonephasestatorwindingof
thealternatorasperthecircuitdiagramusingMCvoltmeterandammeterofsuitable
ranges.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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PROCEDURE TO DRAW GRAPH FOR EMF METHOD:
1. Draw the Open Circuit Characteristic curve (Generated Voltage per phase VS
Field current).
2. Draw the Short Circuit Characteristics curve (Short circuit current VS Field
current)
3. From the graph find the open circuit voltage per phase(E1(ph)for the rated short
circuit current(Isc).
4. By using respective formulae find the Zs, Xs, Eo and percentage regulation.
PROCEDURE TO DRAW GRAPH FOR MMF METHOD:
1. Draw the Open Circuit Characteristic curve (Generated Voltage per phase VS
Field current).
2. Draw the Short Circuit Characteristics curve (Short circuit current VS Field
current)
3. Draw the line OL to represent
PRECAUTIONS:
(i)
The motor field rheostat should be kept in the minimum resistance position.
(ii)
The alternator field potential divider should be kept in the minimum
voltage position.
(iii)
Initially all switches are in open position.
FORMULAE:
1. Armature Resistance Ra=
Ω
2. Synchronous Impedance Zs = O.C. voltage
S.C. current
3. Synchronous Reactance Xs =√Zs2– Ra2
4. Open circuit voltage for lagging p.f =√(VcosΦ +IaRa)2+ (VsinΦ +IaXs)2
5. Open circuit voltage for leading p.f. =√(VcosΦ+IaRa)2+ (VsinΦ –IaXs)2
6. Open circuit voltage for unity p.f =√(V+IaRa)2+(IaXs)2
7. Percentage regulation=(E 0 -V)/V
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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TABULAR COLUMNS:
OPEN CIRCUIT TEST:
Field Current(If)
S. No.
Amps
Open Circuit Line
Voltage (VoL)
Volts
Open circuit Phase
Voltage (Voph)
Volts
1
2
3
4
5
6
7
8
9
10
11
SHORT CIRCUITTEST:
S. No.
Field Current(If)
Short Circuit
Current(120%to 150%of
rated current)(ISC)
MODELGRAPH:
RESULT:
Thus the regulation of 3-phase alternator has been predetermined by the EMF and
MMF methods.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 28
EXP.NO. 6
V AND INVERTED VCURVES OF 3–Φ SYNCHRONOUS MOTOR
AIM:
To draw the V and inverted V curves ofa3 phase Synchronous Motor.
NAMEPLATE DETAILS:
Parameters
Synchronous Motor
DC Generator
Rated Power
Rated Voltage
Rated Current
Rated Speed
APPARATUSREQUIRED:
S. no
Name of Apparatus
Type
1
2
3
4
5
6
Ammeter
Voltmeter
Wattmeter
Rheostat
Tachometer
Connecting Wires
MI
MI
EDM
Wire Wound
Digital
Range
Quantity
THEORY:
The variation of field current effects the power factor at which the synchronous motor
operates. For a synchronous motor, the armature current phasor is given by Ia=V-E where V
is the applied voltage .From the above equation it is clear that the magnitude and phase angle
of phasor Ia depends upon the value of DC excitation. When the syn. Motor is operated at
constant load with variable field excitation, it is observed that:
a) When the excitation is low, the armature current is lag in nature &the magnitude is
comparatively high.
b) If the excitation is gradually increased, the magnitude of Ia is gradually decreasing and the
angle of lag is gradually reduced.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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c) At one particular excitation, the magnitude of Ia corresponding to that load in minimum
and vector will be in phase with V vector.
d) If the excitation is further increased, the magnitude of Ia again gradually increased and Ia
, vector goes to leading state and the angle of load is also gradually increased.
CIRCUIT DIAGRAM: DIAGRAM---6
PROCEDURE:
(1) Note down the name plate details of the motor.
(2) Connections are made as per the circuit diagram..
(3) Close the TPST switch.
(4) By adjusting the auto transformer from the minimum position to the
maximum position the rated supply is given to motor. The motor starts as
an induction motor.
(5) In order to give the excitation to the field for making it to run as the
synchronous motor, close the DPST switch.
(6) By varying the field rheostat note down the excitation current, armature
current and the power factor for various values of excitation.
(7) The same process has to be repeated for loaded condition.
(8) Later the motor is switched off and the graph is drawn.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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PRECAUTION:
(1) The Potential barrier should be in maximum position.
(2) The motor should be started without load.
(3) Initially TPST switch is in open position.
OBSERVATION TABLE:
S.NO
IF
V
IaAm
W1
W2
Amps
Volts
ps
Watts
Watts
W
W1+W2
Watts
COSΦ=
W/(�VLI
L)
1
2
3
4
5
6
7
MODELGRAPHS:
The graph is drawn for-(1) Armature current Vs Excitation current.
(2)Power factor Vs Excitation current.
RESULT: The determination of V and inverted V curves of three phase synchronous motor was
obtained.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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EXP.NO.07
EQUIVALENT CIURCUIT AND PRE-DETERMINATION OF PERFORMANCE
CHARACTERISTICS OF1Ф INDUCTION MOTOR
AIM:
To draw performance characteristics of 1- Ф Induction motor by performing no load blocked
rotor test.
NAMEPLATE DETAILS:
Parameter
1Ф-Induction Motor
Rated Power
Rated Voltage
Rated Current
Rated Speed
APPARATUSREQUIRED:
S. No
1
2
3
4
Name of
Apparatus
Voltmeter
Ammeter
Wattmeter
Connecting wires
Range
Type
Qty.
MI
MI
UPFEDM
THEORY:
A 1-Ф induction motor consists of stator, rotor and other associated parts. In the rotor of a
single phase winding is provided. The windings ofa1-Ф winding(provided)are displaced in
space by120º.A single phase current is fed to the windings so that a resultant rotating
magnetic flux is generated. The rotor starts rotating due to the induction effect produced due
to the relative velocity between the rotor winding and the rotating flux.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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CIRCUIT DIAGRAM: DIAGRAM—7
PROCEDURE:
NO LOAD TEST:
1. Connections are given as per the circuit diagram.
2. Precautions are observed and the motor is started at no load.
3. Autotransformer is varied to have a rated voltage applied.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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BLOCKEDROTOR TEST:
1. Connections are given as per the circuit diagram.
2. Precautions are observed and motor is started on full load or blocked rotor position.
3. Autotransformer is varied to have rated current flowing in motor.
4. Meter readings are the noted.
PRECAUTIONS:
NO LOAD TEST:
∑ Initially TPST Switch is kept open.
∑ Autotransformer is kept at minimum potential position.
∑ The machines must be started on no load.
BLOCKEDROTOR TEST:
∑ Initially the TPST Switch is kept open.
∑ Autotransformer is kept at minimum potential position.
∑ The machine must be started at full load (blocked rotor).
Reff=1.5*Rdc
FORMULAE:
NO LOAD TEST:
∑
∑
∑
∑
∑
cos Ф = Wo/VoIo
Iw=IocosФ
Im =Io sin Ф
Ro = Vo/Iw
Xo =Vo/Im
BLOCKEDROTOR TEST:
Zsc= Vsc/Isc Ω
Rsc= Wsc/Isc2 Ω
Xsc= √(Zsc2– Rsc2) Ω
TABULAR COLUMNS:
NO LOAD TEST:
S.No.
Vo(volts)
Io(amps)
Wo (watts)
1
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 34
BLOCKEDROTOR TEST:
S.No.
Vsc (volts)
Isc (amps)
Wsc(watts)
1
EQUALENT CIRCUIT:
RESULT: Thus the pre-determination of Equivalent circuit parameters and efficiency
of 1-phase induction motor was obtained as follows
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 35
EXP.NO. 08
DETERMINATRION OF Xd AND Xq OF SALIENT POLE SYNCHRONOUS MACHINE
AIM:
To measure Direct Axis (Xd) and Quadreture Axis (Xq) synchronous reactance of Synchronous
machine by performing SLIP Test.
NAMEPLATE DETAILS:
PARAMETERS
DC Shunt Motor
Alternator
Rated Power
Rated Voltage
Rated Current
Rated Speed
Rated field current
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MI
2
Voltmeter
MI
3
Variac
4
Rheostat
Wire Wound
5
Tachometer
Digital
6
Connecting Wires
MI
7
Ammeter
Range
Quantity
THEORY:
In a salient pole alternator, the reactance of magnetic circuit along is along its quad stator
axis. The alternator is driven by auxiliary prime mover at a speed slightly less than the
synchronous speed under these conditions. The armature current is when the armature
current mmf is in line with the field poles. The reactance by the magnetic field current is
minimum. The ratio of maximum voltage to minimum current gives the direct axis
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 36
impedance and the ratio of minimum voltage to maximum current gives the armature axis
impedance.
The values of Xd& Xq are determined by conducting the slip-test. The syn. machine is
driven by a separate prime mover at a speed slightly different from synchronous speed. The
field winding is left open and positive sequence balanced voltages of reduced
magnitude(around 25%of the rated value)and of rated frequency and impressed across the
armature terminals. Here, the relative velocity b/w the field poles and the rotating armature
mmf wave is equal to the difference b/w syn. speed and the rotor speed i.e, the slip speed.
When the rotor is along the d-axis, then it has a position of min reluctance, min flux linkage
and max flux produced links with the winding. Then Xd=(max. armature terminal
voltage/ph) /(min. armature current/ph)As the current is small then Vt
will be high as drop will be small. When the rotor is alongq-axis, then it is max, then the
flux linkage would be max. Then The min flux produced links with winding. So max emf.
Xq =(min. armature terminal voltage/ph) /(max. armature current/ph)
CIRCUIT DIAGRAM: DIAGRAM---8
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 37
PROCEDURE:
1.
2.
3.
4.
5.
6.
7.
8.
Note down the name plate details of motor and alternator.
Connections are made as per the circuit diagram.
Give the supply by closing the DPST switch.
Using the three point starter, start the motor to run at the synchronous speed by
varying the motor field rheostat at the same time check whether the alternator field
has been opened or not.
Apply20%to 30% of the rated voltage to the armature of the alternator by adjusting
the autotransformer.
To obtain the slip and the maximum oscillation of pointers the speed is reduced
slightly lesser than the synchronous speed.
Maximum current, minimum current, maximum voltage and minimum voltage are
noted.
Find out the direct and quadrature axis impedances.
PRECAUTIONS:
1. The motor field rheostat should be kept in minimum.
2. The direction of the rotation due to prime mover and the alternator on the motor
should be the same.
3. Initially all the switches are kept open.
TABULAR COLUMNS:
To find the Direct Axis and Quadrature axis impedances:
S.NO
Vmax
Vmin
Imax
Imin
1
OPEN CIRCUIT TEST:
Field Current(If)
S.No.
Amps
Open Circuit Line
Voltage (VoL)
Volts
Open circuit Phase
Voltage (Voph)
Volts
1
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 38
SHORT CIRCUITTEST:
S.No.
Field Current(If)
Amps
Short Circuit
Current(120%to150% of rated
current)(ISC)
Amps
1
FORMULAE USED:
1. Rac=1.6RacΩ
2. Zd =Vmax/Imin Ω
3. Zq =Vmin/ImaxΩ
4. Xd =√Zd2– Rd2
Ω
5. Xq =√Zq2– Rd2 Ω
6. Id=IasinФamps
7. Iq=Iacos Ф amps
8. %Reg = (Eo-V/V)*100
Where,
Zd =direct axis impedance in Ω
Zq =quadrate axis impedance in Ω
Xd =direct axis reactance in Ω
Xq =quadrate axis reactance in Ω
Id= direct axis current in amps
Ia= quadrate axis current in amps
RESULT: Hence by performing slip test we find the values of Xd=
And Xq=
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 39
EXP.NO. 09
Parallel Operation of Two Single Phase Transformers
AIM:
To operate the given two2KVA, 230/110V singles phase Transformers in parallel and study
the load sharing between them when supplying resisters load.
NAMEPLATE DETAILS:
1Φ- TRANSFORMERS
T/F
T/F-1
HV side
LV side
T/F-2
HV side
LV side
Rated power
Rated voltage
Rated current
Frequency
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MI
2
Ammeter
MI
3
Voltmeter
MI
4
Resistive Load
5
Single phase variac
6
Single Phase Transformer
Range
Quantity
THEORY:
It is economical to install numbers of smaller rated transformers in parallel than installing bigger
rated electrical power transformers. This has mainly the following advantages, to maximize
electrical power system efficiency: Generally electrical power transformer gives the maximum
efficiency at full load. If we run numbers of transformers in parallel, we can switch on only
those transformers which will give the total demand by running nearer to its full load rating for
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 40
that time. When load increases, we can switch none by one other transformer connected in
parallel to fulfill the total demand. In this way we can run the system with maximum efficiency.
To maximize electrical power system availability: If numbers of transformers run in parallel, we
can shutdown any one of them for maintenance purpose. Other parallel transformers in system
will serve the load without total interruption of power.
To maximize power system reliability: if any one of the transformers run in parallel, is tripped
due to fault of other parallel transformers is the system will share the load, hence power supply
may not be interrupted if the shared loads do not make other transformers over loaded.
To maximize electrical power system flexibility: There is always a chance of increasing or
decreasing future demand of power system. If it is predicted that power demand will be
increased in future, there must be a provision of connecting transformers in system in parallel to
fulfill the extra demand because, it is not economical from business point of view to install a
bigger rated single transformer by forecasting the increased future demand as it is unnecessary
investment of money. Again if future demand is decreased, transformers running in parallel can
be removed from system to balance the capital investment and its return.
Conditions for Parallel Operation of Transformers
When two or more transformers run in parallel, they must satisfy the following conditions for
satisfactory performance. These are the conditions for parallel operation of transformers.
1. Same voltage ratio of transformer.
2. Same percentage impedance.
3. Same polarity.
4. Same phase sequence.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 41
CIRCUIT DIAGRAM: DIAGRAM--9
PROCEDURE:
a) Make connections as for circuit diagram, keep the load switch and switch S open.
b) Switch on the mains, seethe volt meter reading of V1 , if this
readingis460V(double the secondary voltage of both the machines) then
switch of and interchange the connections of secondary of any
transformer . if reads zero then the switch S can be closed , this way the
polarities can be checked since wrong polarity will short circuit the
transformers if operated in parallel .
c) Close switch S and then close the load switch.
d) For various values of load current, record terminal voltage, current in two secondary’s,
power supply by the two transformers and the total power,(do not exceed 0 A for total current)
e) Switch of load and switch of main.
f) Determine the equivalent reactance’s and resistance’s of both transformers referred
to HV winding by SC test.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 42
CAULATIONS:
For a given load current ILat an angle ф the current and power supply by each transformer can
be found out by the following formula
IA=(IL)X{(ZB)/(ZA+ZB)}
IB= (IL)X{(ZA)/(ZA+ZB)}
If S is the load KVA, then the KVA shared by the transformers can be found out
by SA= (S)X{(ZB)/(ZA+ZB)}
SB= (S)X{(ZA)/(ZA+ZB)}
Check the result obtained with the Theoretical calculations.
RESULTS:
a) With the help of phasor diagram verify if IA=IB= I.
b) Check if the load share disproportional to the KVA capacities of the respective
transformers
c) From the results state if RA/XA=RB/XB
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 43
EXP.NO. 10
SEPERATION OF CORE LOSSES 1-f TRANSFORMER
AIM: To separate hysteresis and eddy current losses ofagiven1-f transformer.
NAMEPLATE DETAILS:
DC Motor
Alternator
Transformer
Rated Power
Rated voltage
Rated current
Rated speed
Rated field current
APPARATUSREQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MC
2
Voltmeter
MI
3
Wattmeter
EDM
4
Rheostat
Wire wound
5
Potential Divider
Wire wound
6
Tachometer
Range
Quantity
Digital
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 44
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
THEORY:
Hysteresis and eddy current losses are called iron loss and take place in core of the transformer.
Hysteresis loss is given by = Wh = KBmox1.6 f = Af
Eddy current loss also depends on the frequency f and is given by
We = KB2mox f2 t2 =Bf2
B max = Maximum flux density weber / m2
F = frequency cycles/ seconds
t = thickness of stamping
The iron loss will be expressed by
W i = Af +B f2
,
W i/ f = A + B f ,
y=mx+c
This is equation of straight line y = m x + c, when y = w i / f , c = A , and m = B and x = f.
Eddy current and Hysteresis loss can be separated when A and B are found.
The variable frequency supply is obtained from an alternator when frequency can be varied.
CIRCUITDIAGRAM: DIAGRAM--10
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 45
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
PROCEDURE :
(1) Connections are done as per the circuit diagram.
(2) Initially rheostat in the armature circuit of motor is kept at maximum position, the rheostat
in the field circuit of motor is kept at minimum position and the rheostats in the field
circuit (potential divider)of the alternator are kept so that minimum voltage is applied to
the field circuit of the alternator.
(3) Start the motor with the help of 3-point starter
(4) Bring the speed of the motor to the rated speed by using the rheostats of the motor.
(5) By increasing the excitation of alternator using the potential divider bring the voltage of
the alternator to the rated voltage.
(6) Apply the rated voltage to the high voltage side of the transformer by closing the DPDT
switch.
(7) Note down all the meter readings and speed.
(8) Alternator is made to run at different speeds below the rated speed and adjust the voltage
of the alternator, so that v / f ratio is constant.
(9) At each and every speed, note down the readings of voltmeter, ammeter, wattmeter and
the speed of the motor.
(10) Perform the experiment up to 80% of the rated speed and graphs are drawn between
PRECAUTIONS :
(1) Care must be taken about the v / f value constant so that the flux density is maintained
constant.
(2) The rheostat in the field circuit of motor should be minimum position, the rheostat in the
armature circuit of motor should be maximum position and potential divider of alternator
should give voltage to the alternator at the time of starting.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 46
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
TABULAR FORM:
S. no
Voltage
(V)
Wattmeter
reading(W)
Speed
(rpm)
f =PN / 120
V/f
Wi / f
1
2
3
4
5
6
7
8
9
10
11
12
MODELGRAPH:
A
W/ f
f
RESULT:
Separate hysteresis and eddy current losses ofagiven1-f transformer are obtained as follows:
Eddy current losses = Hysteresis losses
Total Core losses=
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 47
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
EXP.NO. 11
SCOTT CONNECTION OF TRANSFORMER
AIM:
To convert three phase system to two phase system with the help of Scott Connection.
NAMEPLATE DETAILS:
Main Transformer
Teaser Transformer
APPARATURS REQUIRED:
SL.NO
Name of the Apparatus
Type
1
Ammeter
MI
2
Ammeter
MI
3
Voltmeter
MI
4
Voltmeter
MI
5
Wattmeter
EDM(LPF)
6
Wattmeter
EDM(UPF)
7
Single phase variac
Range
Quantity
THEORY:
The Scott Connection is also called T-T connection. This scheme of connection is widely used
for 3-f to2-f and vice versa. In this arrangement two transformers are required, one of the two
transformers must have at least two primary and two secondary coils so that a centre tap may be
brought out from each side. The other transformer, known as teaser transformer must have primary
and secondary winding, the number of turns of which are 0.866 times of the respective turns the main
transformer.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 48
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
CIRCUIT DIAGRAM: DIAGRAM –11
PROCEDURE:
(1) Connections are done as per the circuit diagram.
(2) Loads are connected at secondary’s of 2 T/F’s.
(3) Byusing3-f autotransformer apply different voltages to the circuit.
(4) Note down the all the meter readings.
(5) Observe different meter readings.
CALUCULATIONS:
I1T = 2/√3 * K * I2T
Where
K=
I1M = K*I2M
Ib = Ic = √( I1M)2+( I1T/2)2
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Page 49
ST.MARTIN’S ENGINEERING COLLEGE
ELECTRICAL MACHINES-II LAB MANUAL
There fore ,IA = I1T
1) I1T= 1.15*K* I2T
2)
I1M= (K*I2M)2 + (0.5*K* I2T)2
3) If │V2T│=│V2M│ then
[V2T2] + [V2M2] = 2 V2T+ 2 V2M; K=N2/N1
For Balanced Load:
S. No
Load condition
1
2
No load
1 KW load on
both transformers
Teaser transformer
I1T
I2T
V1T
Main transformer
I1M
I2M
V1M V2M
Teaser transformer
I1T
I2T
V1T
Main transformer
I1M
I2M
V1M V2M
For Unbalanced Load:
S.No
Load condition
1
2
No load
1 KW load on
both transformers
RESULT: Therefore the Scott connection has been studied.
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
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