10eel58 transformers and induction machines laboratory

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 Quantity

01 1- Transformer 2 KVA, 230/230V 0102 1- Autotransformer 0-270V,15A 0103 Ammeter 0-1/2 A (MI) 0104 Ammeter 0-10/20 A (MI) 0105 Voltmeter 0-150 V (MI) 0106 Voltmeter 0-300 V (MI) 0107 Wattmeter 1/2A,300V,LPF(0.2) 0108 Wattmeter 10A, 75V,UPF(1) 0109 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.

3. The position of autotransformer adjusted such that voltmeter reads the rated

voltage of the HV 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.

(b) Short Circuit Test:

1. The connections are made as shown in the circuit diagram by keeping the LV side

short circuit.


3. The position of autotransformer adjusted such that ammeter reads the rated current

of the LV winding of the transformer.


Dept. of E & E JCE Belgaum



opened.

Circuit Diagram (1) Open Circuit Test

Fig. 1 Circuit diagram of Open Circuit Test

(2) Short Circuit Test

Fig. 2 Circuit diagram of Short Circuit Test


Specification

Specification


Tabular column

For OC Test

Sl. No.Vo

(volts)Io

(Amps)Wo

(Watts)

01

Specimen Calculation

Wattmeter Constant=Voltage range x Ammeter range x Power FactorFull Scale deflection

Total Iron Loss = W 0 watts

No load power factor cos o=W 0

V 0∗I 0

Coreloss component of no−load current Iw=I 0cos∅ 0 Amps

Magnetic component of no load current I μ=I 0sin∅ 0 Amps

Equivalent Resistance Ro

V o

Iw=

V o

I 0cos∅ 0

Equivalent Reactance X0=V o

I μ=

V o

I 0sin∅ 0

Rated full load current of Transformer= KVARating of Transformer×1000Rated PrimaryVoltage

For S.C.Test

Sl. No.Vs

(volts)Is

(Amps)Ws

(Watts)

01

Total full load copper loss W S = watts.

Equivalent Resistance Refered ¿ primary R0 1=W S

I S2 =¿

Equivalent Impedance Refered ¿ primary Z01=V S

I S=¿



Equivalent RectanceRefered ¿ primary X0 1=√(Z0 12−R0 1

2)

Equivalent Circuit

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



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


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



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?



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.


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.



Circuit diagram

Fig. 1: Circuit diagram


Specification


Tabular column

Sl. No.

Voltmeter(V1)Volts

Ammeter(A1)

Amps

Wattmeter(W1)Watts

Voltmeter(V2)Volts

Ammeter(A2)Amp

Wattmeter(W2)Watts

1



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



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?



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.

Apparatus

Sl.No.


01 1- Transformer 1 KVA, 2KVA 0102 1- Autotransformer 0-270V,15 A 0103 Voltmeter 0-300 V (MI) 0204 Voltmeter 0-600 V (MI) 0105 Ammeter 0-10A (MI) 0206 Ammeter 0-20A (MI) 0107 Wattmeter 300V,10A,UPF 0208 Wattmeter 300V,20A,UPF 0109 Lamp load[ -- 01

10Single Pole Single through Switch (SPST)

--01

11 Single Pole double through Switch (SPDT)

--01

12 Connecting wires -- 15-20

Procedure

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.



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.


3. The position of autotransformer adjusted such that ammeter reads the rated current

of the LV winding of the transformer.



opened.



Circuit Diagram

Fig. 1: Circuit diagram


Specification


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


Specification


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



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


Specification


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



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?



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



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


Specification


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.



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



Specification


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?



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.



Circuit diagram



Specification


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


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



EXPERIMENT NO.7

POLARITY TEST

Aim a) To conduct polarity test on transformer. Apparatus

Sl.No.


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



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



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.

Apparatus:

Sl.No.

Equipment Range Quantity

1 1- transformer 2KVA, 400 / 220 V 32 3- dimmer stat 0-415 V, 10 Amps 13 Voltmeter(MI) 0-600V 14 Voltmeter(MI) 0-300V 15 Ammeter 0-25A 16 Ammeter 0-5A 17 Multimeter 0-750 V 28 3- resistive load - 19 Patch chords - -

Theory:

Procedure:

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



= 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:



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.

10. Load test on- induction generator.

11. Load test on single- phase induction motor.


10eel58 transformers and induction machines laboratory

Documents

b short circuit test

procedurea open circuit

short circuit tests

efficiency of transformer

sc test

position of autotransformer

supply switch

leadinglagging power