Transformer and Induction Machines Lab EXPERIMENT NO.1 OC AND SC TEST ON SINGLE PHASE TRANSFORMER Aim: (a) To conduct open circuit and short circuit tests on single phase transformer. (b) Predetermine efficiency, regulation for different loads and power factor. (c) To draw the equivalent circuit and represent all the parameter. Apparatus: Sl. No. Apparatus Range Quanti ty 01 1-Transformer 2 KVA, 230/230V 01 02 1-Autotransforme r 0-270V,15A 01 03 Ammeter 0-1/2 A (MI) 01 04 Ammeter 0-10/20 A (MI) 01 05 Voltmeter 0-150 V (MI) 01 06 Voltmeter 0-300 V (MI) 01 07 Wattmeter 1/2A,300V,LPF(0. 2) 01 08 Wattmeter 10A, 75V,UPF(1) 01 09 Connecting wires ---- 15-20 Procedure (a) Open Circuit Test: 1. The connections are made as shown in the circuit diagram by keeping HV side open. 2. With the autotransformer at zero position, the supply switch is closed. Dept. of E & E JCE Belgaum Page 1
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10eel58 Transformers and Induction Machines Laboratory
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Transformer and Induction Machines Lab
EXPERIMENT NO.1
OC AND SC TEST ON SINGLE PHASE TRANSFORMER
Aim: (a) To conduct open circuit and short circuit tests on single phase transformer.
(b) Predetermine efficiency, regulation for different loads and power factor.
(c) To draw the equivalent circuit and represent all the parameter.
Fig. 3: Equivalent circuit of transformer referred to primary side
Tabular column
Sl.No.
Power Factor
Load Factor X
O/p power (Watts)
%
01
UPF
0.2502 0.503 0.7504 105 1.2501
0.6 PF
0.2502 0.503 0.7504 105 1.25
Specimen calculation
X= Fraction of Full load Current
%= Output powerOutput power+ losses
= X∗KVA ¿103∗cos∅X∗KVA¿103∗cos∅+W 0+X 2∗W SC
x 100
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Transformer and Induction Machines Lab
Tabular ColumnSl.No.
leading/laggingPower Factor % Regulation
01
Leading
0.202 0.403 0.604 0.805 101
Lagging
0.202 0.403 0.604 0.805 1
Specimen calculation
Total Voltage drop as referred to secondary:
For lagging pf = V⃗ 0-V⃗ L = Is R01 cos + Is X01 sin
For leading pf = V⃗ 0-V⃗ L = Is R01 cos - Is X01 sin
%Regulation=V 0−V L
V 0
Nature of Graph
Fig. 4: Efficiency V/S Output power
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Transformer and Induction Machines Lab
Fig. 5: Power factor V/S Regulation
Viva Questions
1. How are the meter ratings selected for O.C and S.C tests?
2. Why is the O.C. test conducted on the L.V. side of the transformer and S.C test
on H.V. side?
3. What are the losses measured in an O.C. test?
4. What are the losses measured in an S.C. test?
5. What is the condition for maximum efficiency in a transformer?
6. What is meant by ‘regulation’ of a transformer?
7. Is a high or low value of regulation preferred? Why?
8. How can the parameters on one side of the transformer be transferred to the other side?
9. Why efficiency of transformer is high as compare to other electrical machines?
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Transformer and Induction Machines Lab
EXPERIMENT NO.2
DETERMINATION OF EFFICIENCY BY SUMPNER’S TEST
Aim: (a) To conduct Sumpner’s test or back to back test on two identical single phase transformers.
(b) To determine efficiency for different loads & power factor.
ApparatusSl.No.
Apparatus Range Quantity
01 1- Transformer 2 KVA 0202 1- Autotransformer 0-270V,15A 0103 Voltmeter (MI) 0-600 V (MI) 0104 Voltmeter (MI) 0-300 V (MI) 0105 Voltmeter (MI) 0-150 V (MI) 0106 Ammeter (MI) 2 A (MI) 0107 Ammeter (MI) 0-10 A (MI) 0208 Wattmeter 2A,300V,LPF 0109 Wattmeter 10A,75V,UPF 0110 SPST Switch ---- 0111 Connecting wires ---- 15-20
Procedure1. The connections are made as shown in circuit.
2. With autotransformer at zero position and switch 2 as well as SPST switch at open
supply switch 1 is closed.
3. The autotransformer 1 in the primary circuit is adjusted such that voltmeter V1 reads the
rated voltage of transformer.
4. The voltmeter Vref is referred for zero readings. If the voltmeter shows zero the SPST
switch is closed.
5. If Vref results the double the voltage appears, interchange primary connection of any one
transformer.
6. The supply switch 2 is closed ensuring that the autotransformer 2 in the secondary circuit
is at zero position.
7. The output of autotransformer 2 in the secondary circuit is adjusted such that the
ammeter connected in the circuit reads the rated current of the transformer and all the
meter readings are noted in to the tabular column.
8. The autotransformer 1 and 2 is brought back to zero position and open the both the
supply switches.
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Transformer and Induction Machines Lab
Circuit diagram
Fig. 1: Circuit diagram
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Specification
Transformer and Induction Machines Lab
Tabular column
Sl. No.
Voltmeter(V1)Volts
Ammeter(A1)
Amps
Wattmeter(W1)Watts
Voltmeter(V2)Volts
Ammeter(A2)Amp
Wattmeter(W2)Watts
1
Specimen calculation
Wattmeter Constant=Voltage range x Ammeter range x Power FactorFull Scale deflection
W1 = Core or constant loss Watts
W2 = Copper loss of the transformer Watts
Efficiency of transformer= X∗cosΦ∗103
X∗cosΦ∗103+(W 12 )+X2∗(W 2
2 )Tabular column
S. No. Load (X) pf (UPF) Efficiency01 0.25 Full load02 0.50 Full load03 0.75 Full load04 Full load
X= load factor
S. No. Load (X) pf (0.6) Efficiency01 0.25 Full load02 0.50 Full load03 0.75 Full load04 Full load
X= load factor
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Transformer and Induction Machines Lab
Nature of graph
Fig. 2: Efficiency V/S Output power
Viva questions
1. Which parameters are determined from this test
2. Why transformer rating in kVA
3. Why similar transformers are used in this experiment4. What is the advantages of back to back test.5. Weather O. C. and S. C. test on transformer yields better figure of merit or Sumpner’s
test? Why?
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Transformer and Induction Machines Lab
EXPERIMENT NO.3
PARALLEL OPERATION OF TWO SINGLE PHASE TRANSFORMERS
Aim a) To operate two dissimilar single phase transformer in parallel.
b) To observe the load sharing by each transformer.
1. The connections are made as shown in circuit diagram.
2. With the autotransformer at zero position and the load switch as well as SPST
switch at open position, the supply switch is closed.
3. The autotransformer position is adjusted such that voltmeter V1 reads the rated
voltage of the transformer.
4. The voltmeter V2 is verified for zero reading if the voltmeter shows zero then
SPST switch is closed.
5. If V2 results the double the voltage appears, interchange primary connection of any
one transformer.
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Transformer and Induction Machines Lab
6. The load switch is closed the load is applied in step by step and at each step all
the corresponding meter readings are noted in to the tabular column.
7. The load is applied in steps until the rated current of the transformer are reached
8. The load is removed in steps, the load switch is opened and the autotransformer is
brought back to zero position and supply switch is opened.
Procedure for Short Circuit Test
1. The connections are made as shown in the circuit diagram by keeping the LV side
short circuit.
2. With the autotransformer at zero position, the supply switch is closed.
3. The position of autotransformer adjusted such that ammeter reads the rated current
of the LV winding of the transformer.
4. Note down the corresponding all meter readings in tabular column.
5. The autotransformer is brought back to zero position and the supply switch is
opened.
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Transformer and Induction Machines Lab
Circuit Diagram
Fig. 1: Circuit diagram
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Specification
Transformer and Induction Machines Lab
Tabular Column
S.NO
Supply Voltage
Vs (volts)
Transformer A Transformer B Load
I1 (amps)
W1 (watts
)
I2 (amps)
W2 (watts)
VL (volts)
IL
(amps)WL
(watts)
ActualTheoretical
(Ῑ1)Actual Actual
Theoretical
(Ῑ2)Actual
ActualTheoretica
l(Ῑ L=Ῑ1+ Ῑ2)
ActualTheoretical(WL= W1+
W2)
1
2
3
4
5
6
Short Circuit test Circuit Diagram
Fig. 2: Circuit diagram for short circuit test
Tabular Column
SNO Transformer KVA of Transformer Vs (volts)
Is
(Amps)Ws
(Watts)1 A2 B
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Specification
Transformer and Induction Machines Lab
Sample calculation
From short circuit test
Transformer ‘A’
R02a=W Sa
I sa2 Ω
Z02a=V Sa
I saΩ
X 02a=√(Z02a)2−(R02a)
2Ω
Transformer ‘B’
R02b=W Sb
I sb2 Ω
Z02b=V Sb
I sbΩ
X 02b=√(Z02 b)2−(R02b)
2Ω
For parallel operation
cosΦ=W L
V L x I L
W L=W 1+W 2
I 1=(I ¿¿ l∠−Φ)∗Z02 b
Z02 a+Z02 b
¿
I 2=( I l∠−Φ)∗Z02a
Z02a+Z02b
Viva question
1. Conditions for parallel operation
2. It is possible to operate transformers of different KVA rating in parallel3. What happen when transformer secondary terminals are connected with wrong
polarity4. What is meant by circulating current in parallel operation of two transformers
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Transformer and Induction Machines Lab
5. Why all transformers cannot operate in parallel
EXPERIMENT NO. 4
LOAD TEST ON THREE PHASE INDUCTION MOTOR
Aim: To obtain performance curve of three phase induction motor (mechanical load) BHP vs Efficiency, BHP vs Slip, BHP vs Power factor and Torque vs Speed
Apparatus Required
Sl. No. Equipment Range Quantity01 Ammeter 0-10 A (MI) 0202 Voltmeter 0-600V (MI) 0103 Wattmeter 600V, 10A, UPF 0104 Autotransformer 0-440V 0105 Connecting wires ---- 15-20
Procedure
1. Make the connection as shown in circuit diagram.2. Keeping break drum free, the supply is closed (Pour water in the break drum before
closing the switch).3. The DOL starter button is pressed to run the induction motor and no load reading is
noted down.4. The induction motor current is increased by tightening the brake drum till the rated
current, At each step all the meter reading are noted including the speed the motor.5. The brake drum is made free and then the starter STOP button is pressed. The supply
switch is opened.
Circuit diagram
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Specification
Transformer and Induction Machines Lab
Fig. 1 Circuit diagram
Tabular column
S. No.
Ammeter(I)
(Amps)
Voltmeter(V)
(Volts)
Wattmeter(Watts)
WWatts
Speed(RPM)
Spring Load (kg)
S1 ~
S2
Torque(N-M)
%ɳ
Slip
pf
W1 W2 W=W1+W2
S1 S2
01
02
03
04
Sample calculation
Synchrous speed=120 fP
Torque = (S1 /͂ −¿S2)*rDiameter of drum (d) =0.22 mRadius of drum (r) = 0.11 m
BHP=2π NT4500
Output = BHP x 735.6 kW
% ɳ= Out putInput (Wattmeter reading)
x 100
Pf= W
√3V∗I
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Transformer and Induction Machines Lab
Nature of graph
Viva Questions
1. How are the meter ratings selected for this experiment?
2. Why does one of the watt meters read -ve at starting?
3. What is ‘slip’ in an induction motor?
4. What are the two types of 3 phase induction motors and what is the difference between the
two?
5. What is the value of slip at starting?
6. What are the advantages of induction motor?
7. What is the condition for maximum torque in an induction motor?
8. What are the different losses in an induction motor?
9. Give some applications induction motor?
10. Explain a typical Torque-slip characteristic.
11. What is the effect of increased rotor resistance on the performance of an induction
machine?
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Transformer and Induction Machines Lab
EXPERIMENT NO. 5
LOAD TEST ON SINGLE PHASE INDUCTION MOTOR
Aim: To obtain performance curve of single phase induction motor (mechanical load)
BHP vs Efficiency, BHP vs Slip, BHP vs Power factor and Torque vs Speed
Apparatus Required
Sl. No. Equipment Range Quantity01 Ammeter 0-20 A (MI) 0102 Voltmeter 0-250V (MI) 0103 Wattmeter 250V, 10A,
UPF 01
04 Autotransformer 0-300V 0105 Lug wires - 15-20
Procedure
1. Make the connection as shown in circuit diagram2. Keeping the autotransformer in minimum position and break drum free, the supply is
closed (Pour water in the break drum before closing the switch)3. Apply the rated voltage by gradually varying the single phase autotransformer4. No load current, voltage and wattmeter reading are noted, including the speed the
motor5. Current the induction motor current is increased by tightening the break drum till the
rated current is attained. At each step all the meter reading are noted down including the speed the motor
6. The brake drum is made free and then the starter STOP button is pressed. The supply switch is
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Transformer and Induction Machines Lab
Circuit Diagram
Fig. 1 Circuit diagram
Tabular column
S. No.
Ammeter(I)
(Amps)
Voltmeter(V)
(Volts)
Wattmeter(Watts)
Speed(RPM)
Spring Load(kg)
S1 ~ S2
Torque(N-M)
%ɳ Slip pf
S1 S2
01020304
Sample calculation
Synchrous speed=120 fP
Torque = (S1-S2)*rDiameter of drum (d) =0.22 mRadius of drum (r) = 0.11 m
BHP=2π NT4500
Output = BHP x 735.6 kW
% ɳ= Out putInput (Wattmeter reading)
Pf = WV∗I
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Specification
Transformer and Induction Machines Lab
Nature of graph
Viva Questions
1. Why single phase motors most commonly used
2. Why single phase induction motor are not self starting
3. How all you resolve a single phase pulsating field
4. Is the starting torque developed by the single phase motor is zero.
5. Explain a typical Torque-slip characteristic.
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Transformer and Induction Machines Lab
EXPERIMENT NO.6
SPEED CONTROL OF THREE PHASE INDUCTION MOTOR BY VARYING ROTOR RESISTANCE
Aim: Controlling the speed of three phase induction motor by varying the rotor resistance
Apparatus required
Sl. No. Equipment Range Quantity01 Ammeter 0-10 A (MI) 0102 Voltmeter 0-600V (MI) 0103 Rotor resistance ---- 0104 Multimeter ---- 0105 Connecting wires ---- 15-20
Procedure
1. Make the connection as shown in circuit diagram2. Supply switch is closed and motor is started with the help of DOL starter3. Without adding any load insert the resistance to each three phase winding, note down
the corresponding current, speed and voltmeter after adding resistance4. Repeat the above procedure by adding different resistance5. Starter STOP button is pressed. The supply switch is opened.
Circuit diagram
Fig. 1 Circuit diagram
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Specification
Transformer and Induction Machines Lab
Tabular column
S. No. Resistancein steps
Speed(RPM)
Current(Amps)
Resistance(Ohm)
Voltage(Volts)
1234
Nature of graph
Viva questions
1. What is the effect of increased rotor resistance on the performance of an induction
machine?
2. How the squirrel cage induction motor is different from a wound rotor motor in
performance?
3. Rotor resistance starting is preferred to reduce voltage starting for wound rotor
induction motor why?
4. On what factors does the speed of induction motor defers?
Dept. of E & E JCE Belgaum Page 23
Transformer and Induction Machines Lab
EXPERIMENT NO.7
LOAD TEST ON THREE, SINGLE PHASE TRANSFORMERS
CONNECTED IN STAR DELTA FORMAT
Aim: To determine the efficiency of a three, single phase transformers connected in star-delta by direct loading.
Apparatus required
Sl. No. Equipment Range Quantity01 Ammeter 0-10 A (MI) 0202 Ammeter 0-5 A (MI) 0203 Voltmeter 0-600V (MI) 0104 Wattmeter 600V, 10A, UPF 0405 Connecting wires ---- 15-20
Procedure
1. Make the connection as shown in circuit diagram2. Care should be taken to see that the star point on the primary side are obtained by
connecting all similar terminals.3. With the three phase auto transformers set at minimum position, the supply switch is
closed 4. Apply the rated voltage with the help of auto transformer.5. Now the transformer is loaded using a three phase resistive load. The load is increased
in steps. At each step note down the all meter reading.6. The load on transformer is increased till the full load current.7. The load is removed step by step, the load switch is opened, the three phase
autotransformer is bring to minimum position and supply switch is opened.
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Transformer and Induction Machines Lab
Circuit diagram
Fig. 1 Circuit diagram
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Specification
Transformer and Induction Machines Lab
Tabular column
S. No.
Star connection Delta W1
(watts)
W2
(Watts)Efficiency % Reg.
1 Vph Vline Iph Iline Vph Vline Iph Iline
234
Specimen Calculation
Wattmeter Constant=Voltage range x Ammeter range x Power FactorFull Scale deflection
3−ΦPower (P )=√3∗V L∗I L∗cosΦ
%Efiiciency=W 2
W 1
x100
%Regulation=V ph∗N L−V ph∗FL∗100
V ph∗N L
Nature of graph
Dept. of E & E JCE Belgaum Page 26
Transformer and Induction Machines Lab
EXPERIMENT NO.7
POLARITY TEST
Aim a) To conduct polarity test on transformer. Apparatus
Sl.No.
Apparatus Range Quantity
01 3 Dimmer state 0-415 V 10 A 0102 Voltmeter 0-300 V 0303 1 Transformer 1 KVA 01
Procedure:(1) Make the connection as per the circuit diagram (a) and (b)(2) With autotransformer in minimum position switch is closed(3) Apply the rated supply by varying autotransformer(4) Noted down the volt meter reading. If the polarities of transformer is same then resultant
voltage should be difference of the two transformer i.e. V= V1 - V2(5) If the polarities of transformer are different then resultant voltage should be sum of the
two transformer i.e. V= V1 + V2
Circuit Diagram:
Correct Polarity
Reverse Polarity
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Transformer and Induction Machines Lab
Tabular column
Correct Polarity
Sl.No
V1 (Volts)
V2 (Volts)
V(Volts)
Polarity
1234
Reverse Polarity
Sl.No
V1 (Volts)
V2 (Volts)
V(Volts)
Polarity
1234
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Transformer and Induction Machines Lab
TITLE: STAR DELTA CONNECTION OF TRANSFORMER
Aim: - (a) To find two polarities of primary and secondary windings of given three single phase Transformer.
(a) To verity the voltage & current relations in star delta connection.(b) To determine the efficiency & regulation for balanced load at UPF.
1. The connections are made as shown in circuit diagram.2. With the autotransformerat zero output and load switch open supply switch
is closed.3. The output of autotransformeris adjusted such that voltmeter connected in
the primary circuit reads rated voltage of transformer & all the voltmeter readings on no load are noted in to the tabular column.
4. The load switch is closed, the load is applied in step & all the meter readings are noted in to the tabular column for each steps.
5. The load is applied in steps until the rated current of transformer is reached & all the meter readings are noted in to the tabular column for each step.
6. The load is removed in steps, the load switch is opened, the autotransformeris brought back to zero output & supply switch is opened.
Tabular Column:
Sl.No.
Star Connection Delta Connection
VL in Volts
Vph in
Meas
Vphcal cul
IL inAmp
Iph inAmp
VL inVolts
Vph inVolts
IL inAmp
Iph inMeas
Iph inCalc
01020304
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Transformer and Induction Machines Lab
= W1=3 VL IL cos = W2=3 VL IL cos
Sl.No.
Star Connection Delta Connection
Vph inV
Iph inA
W1 in W
Vph inV
Iph inA
W2 in W
Efficiency%
% Regulation % R
01020304
Specimen Calculation of Reading No-2:
Rated full loadCurrent of transformer (IFL)=KVARating of transformerRated primary voltage
3−Power W=√3V L I Lcos
%Efficiency=W 2W 1
x 100
%Regulation=V ph NL – VphFL x 100V p hNL
Circuit Diagram:
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Transformer and Induction Machines Lab
TRANSFORMERS AND INDUCTION MACHINES LABORATORY
Subject Code: 10EEL58 IA Marks: 25No. of Practical Hrs./ Week : 03 Exam Hours : 03Total No. of Practical Hrs. : 42 Exam Marks : 50
1. (a) Predetermination of efficiency and regulation by Open Circuit and Short circuit tests on single - phase transformer.
(b) Calculation of parameters of equivalent circuit from the readings of the tests and determination of efficiency and regulation from the equivalent circuit to co-relate results obtained earlier.
2. Sumpner’s test on similar transformers and determination of combined and individual transformer efficiency.
3. Parallel operation of two dissimilar (different kVA) single-phase transformers and determination of load sharing and analytical verification given the Open Circuit and Short circuit tests details.
4. Polarity test and connection of 3 single-phase transformers in star – delta and determination of efficiency and regulation under balanced resistive load.
5. Scott connection with balanced and unbalanced resistive loads.
6. Load test on 3-phase induction motor- and plot of Torque versus speed, output hp versus efficiency, power factor and slip.
7. Predetermination of performance of 3-phase induction Motor from the Circle diagram.
8. (a)Determination of parameters of the equivalent circuit of a 3-phase Induction Motor by conducting NO load and Blocked rotor tests.
(b)Determination of performance quantities of the induction motor from the equivalent circuit to correlate the results obtained from the load test or circle diagram.
9. Speed control of 3-phase induction motor by varying rotor resistance.