269010454 electrical-machines-lab-manual-for-petrochemaical

RVS COLLEGE OF ENGINEERING &TECHNOLOGY

(Approved by AICTE and affiliated to Anna University- Chennai)

Kumaran Kottam., Sulur, Coimbatore - 641402.

DEPARTMENT OF

ELECTRICAL AND ELECTRONICS ENGINEERING

ELECTRICAL MACHINES

LABORATORY LAB MANUAL

R2013

STUDENT NAME : …………………………………..

REGISTER NUMBER : …………………………………..

DEPARTMENT: …………………………………..

Lab Manual: Electrical Machines Laboratory (EI6411) Regulation 2013

1

EI6411 ELECTRICAL MACHINES LABORATORY L T P C

0 0 3 2

OBJECTIVE:

To impart hands on experience in verification of circuit laws and theorems, measurement of

circuit parameters, study of circuit characteristics and simulation of time response. To expose

the students to the basic operation of electrical machines and help them to develop experimental

skills.

LIST OF EXPERIMENTS.

1. Open circuit characteristics of D.C. shunt generator.

2. Load characteristics of D.C. shunt generator.

3. Load test on D.C. Shunt Motor.

4. Load test on D.C. Series Motor.

5. Swinburne’s test

6. Speed control of D.C. Shunt Motor.

7. Load test on Single Phase Transformer

8. Open circuit and Short circuit tests on Single Phase Transformer (Determination of

equivalent circuit parameters).

9. Load test on Single Phase Induction Motor.

10. No load and blocked rotor tests on Three Phase Induction Motor (Determination of

equivalent circuit parameters)

11. Load test on Three Phase Induction Motor.

12. Study of Starters

TOTAL: 45 PERIODS

OUTCOME:

Ability to understand and analyze Instrumentation systems and their applications to

various industries.


2

CYCLE I

CYCLE II


3

SUMMARY OF EXPERIMENTS

(Fill in the order by which done)

Ex.No. Date Experiment Name Page No. Mark Staff Signature

1

2

3

4

5

6

7

8

9

10

11

12

Average


4

CIRCUIT DIAGRAM FOR OPEN CIRCUIT ON SEPERATELY EXCITED DC GENERATOR

FUSE RATING

125% of rated current.

NAME PLATE DETAILS


5

OPEN CIRCUIT TEST CHARACTERISTIC OF SEPARATELY

EXCITED DC GENERATOR

AIM:

To conduct the open circuit test on a given separately excited dc generator and

draw the characteristic curves.

APPARATUS REQUIRED:

S.NO APPARATUS TYPE RANGE QUANTITY

1. Voltmeter MC (0-300)V 1

2. Ammeter MC (0-2) A 1

3. Rheostat Wire Wound 400 Ω / 1.1 A 1

4. Rheostat Double element 350 Ω / 2A 1

5. Tachometer Digital - 1

6. Connecting Wires - - As Req.

FUSE RATING:

110-125% of rated current (full load current).

PRECAUTION:

The motor field rheostat should be kept at minimum resistance position.

The generator field rheostat should be kept at maximum resistance position.

FORMULAE USED:

1. Generated voltage Eg = VL + IaRa in Volts.

Where, VL – Load voltage in Volts.

Ia - Armature current in Amps.

Ra - Armature resistance in Ohms.


6

CIRCUIT DIAGRAM FOR ARMATURE RESISTANCE

TABLE 1: OPEN CIRCUIT TEST

S. No

Field current

(If)

Amps

Open Circuit Voltage

(Eo)

Volts


7

PROCEDURE:

OPEN CIRCUIT TEST:

1. Note down the nameplate details of motor.

2. Connections are made as per the circuit diagram shown in diagram.

3. Initially SPST Switch is kept open.

4. Supply is given by closing the DPST Switch in the motor side.

5. Using the DC three point starter, start the motor.

6. The field rheostat of motor is adjusted to run the motor at rated speed.

7. Emf generated due to residual magnetism in the generator is noted along with the zero

value field current.

8. Then, the SPST Switch is closed. Increase the field current in steps of 0.1 Amps by

varying the resistance of the generator field and note down the corresponding open

circuit voltages in Table (1).

TO FIND ARMATURE RESISTANCE:


2. Supply is given by closing the DPST Switch and increase the load step by step.

3. Enter the corresponding ammeter and voltmeter readings in Table (2).


8

TABLE 2: TO FIND ARMATURE RESISTANCE

S. No. Current Ia (Amps) Voltage V (Volts) Ra=V/Ia ( )

Average value of R a=

MODEL GRAPH:

MODEL CALCULATION:


9

RESULT:

VIVA QUESTIONS:

1. What is the function of carbon brush used in D.C generator?

2. What is meant by self-excited and separately excited dc generator?

3. What is the basic difference between dc generator and dc motor

4. Write down the emf equation of dc generator. Give the meaning of each symbol.

5. What is critical resistance of a DC shunt generator?

6. What are the conditions to be fulfilled for a shunt generator to build up Voltage?

7. What do you mean by residual flux in DC generator?


10

CIRCUIT DIAGRAM FOR LOAD TEST ON SELF EXCITED DC SHUNT GENERATOR

FUSE RATING


NAME PLATE DETAILS


11

LOAD TEST ON SELF EXCITED DC SHUNT GENERATOR

AIM:

To conduct the load test on a given self-excited dc shunt generator and draw the

characteristic curves.

APPARATUS REQUIRED:


1. Voltmeter MC (0-300)V 1

2. Ammeter MC (0-10) A

(0-2) A

1

1

3. Rheostat Wire Wound 400 Ω / 1.1 A

360 Ω / 2 A Each 1


5. Connecting Wires - - As Req.

6 Loading Rheostat Wire Wound - 1

FUSE RATING:


PRECAUTIONS:

1. All connections should be perfectly tight and no loose wire should lie on the work

table.

2. Before switching ON the dc supply, ensure that the starter’s moving arm is at its

maximum resistance position.

3. There should be no load on the motor at the time of starting.

4. At the time of starting, the field circuit rheostat is in minimum resistance position.

5. Hold the tachometer with both hands steady and in line with the motor shaft so that it

reads correctly.

FORMULAE USED:

1. Generated voltage (Eg) = VL + Ia Ra in Volts.

Where,

VL- Load voltage in Volts.

Ia- Armature current in Amps & Ra- Armature resistance in Ohms.


12


TABLE 1: LOAD TEST

S. N

o

IL

Amps

If

Amps

Ia= IL- If

Amps

Terminal

Voltage

(VL)

Volts

Ia Ra

Volts

E g =VL + IaRa

Volts


13

PROCEDURE:

LOAD TEST:

1. Note down the nameplate details of motor.

2. Connections are made as per the circuit diagram shown diagram.

3. Supply is given by closing the DPST Switch in the motor side.

4. Using the DC three point starter, start the motor.

5. The field rheostat of motor is adjusted to run the motor at rated speed.

6. The generator field rheostat is adjusted for the rated voltage.

7. The DPST switch in the generator side is closed. Increase the resistive load in steps of

2 Amps and note down the corresponding load current and terminal voltage values in

Table (1).

8. Then the resistive load is gradually decreased and the DPST Switch on the generator

side is open. Then the supply is switched off.

9. The generated voltage Eg is calculated by using the formulae as mentioned above and

enter the values in the Table (1).

TO FIND ARMATURE RESISTANCE:


2. Supply is given by closing the DPST switch and increases the load step by step.



14

TABLE 2: TO FIND ARMATURE RESISTANCE.

S. No.

Current

Ia

(Amps)

Voltage

V

(Volts)

Ra=V/Ia

( )

Average value of R a=

MODEL GRAPH:

MODEL CALCULATION:


15

RESULT:

VIVA QUESTIONS:

1. State the various types of DC generators.

2. List the main parts of DC machine.

3. State the applications of various types of DC generators.

4. What is residual voltage?

5. Difference between self-excited and separately excited of DC generator.


16

CIRCUIT DIAGRAM FOR LOAD TEST ON D.C SHUNT MOTOR

FUSE RATING


NAME PLATE DETAILS


17

LOAD TEST ON DC SHUNT MOTOR

AIM:

To conduct the load test on DC shunt motor and draw the characteristic curves.

APPARATUS REQUIRED:

S. No APPARATUS TYPE RANGE QUANTITY

1 Ammeter MC (0-20) A 1

2 Voltmeter MC (0-300) V 1

3 Tachometer Digital - 1

4 Rheostat Wire Wound

wound

400 Ω/ 1.1 A 1

5 Connecting Wires - - As Req.

FUSE RATING:


PRECAUTIONS:


table.






reads correctly.

FORMULAE USED:

1. Torque T = (S1~S2) × (R) × 9.81 in N-m.

Where,

R- Radius of the Brake drum in m.

t- Thickness of the Belt in m.

S1, S2- Spring balance reading in Kg.


18

TABULATION:

Radius of the brake drum:

S. No

Load

Current

(IL)

Amps

Load

Voltage

( VL )

Volts

Input

Power

( Pi )

Watts

Speed

( N )

rpm

Spring Balance Reading

(Kg)

Torque

(T)

N-m

Input

Power

(Pin)

Watts

Output

Power

(PO)

Watts

Efficiency

( η )

% S1 S2 S1~S2


19

2. Input power = VL × IL in Watts.

Where,

VL - Load Voltage in Volts.

IL -Load current in Amps.

3. Output power = 2πNT/60 in Watts.

Where,

N- Speed of the armature in rpm.

T- Torque in N-m.

4. Percentage of Efficiency = (Output power/Input power) × 100.

PROCEDURE:

1. Connections are given as per the circuit diagram.

2. Using the three-point starter the motor is started to run at the rated speed by adjusting

the field rheostat if necessary.

3. The meter readings are noted at no load condition.

4. By using the Brake drum with spring balance arrangement the motor is loaded and the

corresponding readings are noted up to the rated current.

5. After the observation of all the readings the load is released gradually.

6. Load is gradually decreased and field rheostat is brought to the minimum resistance

position and the supply is switched off.


20

MODEL GRAPH:

Electrical Characteristics Mechanical Characteristics

MODEL CALCULATION:


21

RESULT:

VIVA QUESTION:

1. How do you load the motor in this experiment?

2. What was the assumption made in calculations?

3. What is the condition for maximum torque of a D.C. shunt motor?

4. Why is the starter necessary?

5. What is the power factor of the load used?


22

CIRCUIT DIAGRAM FOR LOAD TEST ON D.C. SERIES MOTOR

FUSE RATING


NAME PLATE DETAILS


23

LOAD TEST ON D.C. SERIES MOTOR

AIM:

To conduct load test on DC series motor and determine the load characteristics.

APPARATUS REQUIRED:


1. Voltmeter MC (0-300V) 1

2. Ammeter MC (0-20A) 1


4. Connecting wires - - As Req.

PRECAUTIONS:

The series motor should be started with some minimum load.

Water should be poured in the hollow portion of brake drum.

Motor should be stopped with some minimum load.

After shut down, the load should be fully released, so as to make the drum free of cool.

FORMULAE USED:

1 . Torque applied on the motor, T = (S1~S2) x r x 9.81 Nm.

2. Input Power (Pi) = VL x IL Watts.

Output, P0 = (2πNT)/60 Watts.

3. % Efficiency, η = (Po/Pi) x 100.

Where,

Circumference of the brake drum, 2 π r = ---------- m2

Radius of the brake drum, r = ---------- m

S1&S2 spring balance readings in kg.


24

TABULATION:

Sl. No

Line

voltage

VL Volts

Line

current

IL

Amps

Speed

N

(rpm)

Spring balance

reading

Torque

T (N.m)

Output Power

P0

Watts

Input Power

Pi

Watts

% Efficiency

η

S1

Kg

S2

Kg

1

2

3

4

5


25

PROCEDURE:

1. Connections are made as per the circuit diagram.

2. Supply is given by closing DPSTS.

3. Start the motor using the starter.

4. Note down the readings for varying load conditions and plot the graph.

MODEL CALCULATION:

RESULT:

VIVA QUESTIONS:

1. Why the series motor is started with some minimum load?

2. What are the applications of D.C. series motor?

3. Why series motors are used for traction purpose?

4. While running, if series field winding is opened what happens?


26

CIRCUIT DIAGRAM FOR SWINBURN’S TEST

FUSE RATING


NAME PLATE DETAILS


27

SWINBURNE’S TEST

AIM:

To predetermine the efficiency of a given dc shunt machine when working as a motor

as well as generator by Swinburne’s test and also draw the characteristic curves.

APPARATUS REQUIRED:


1. Voltmeter MC ( 0-300 ) V

( 0-50 ) V

1

1

2. Ammeter MC (0-5) A

(0-2) A

1

1

3. Rheostat Wire

Wound

400 Ω / 1.1 A

1

4 Loading Rheostat Wire

Wound 50 Ω / 5 A 1


6. Connecting Wires - - As Req

FUSE RATING:


PRECAUTIONS:


table.






reads correctly.


28


TABLE 1: TO FIND CONSTANT LOSSES

TABLE 2: TO FIND ARMATURE RESISTANCE ‘R a’

S.NO INPUT

SUPPLY

VOLTAGE

(Volts)

NO LOAD

CURRENT

I 0

(Amps)

FIELD

CURRENT

I f (Amps)

ARMATURE

CURRENT

Iao = I 0 - I f (Amps)

CONSTANT

LOSSES

Wo

= VI 0 – I ao2 R a

(Watts)

S.NO CURRENT

Ia

( Amps )

VOLTAGE

V

( Volts )

ARMATURE RESISTANCE

Rdc = V / I a

(Ohms)

1.

2.

3.

4.

5.

Average value of Ra =


29

FORMULAE USED:

1. Armature Current on no load, I ao = I 0 – I f

2. Constant losses, W c = VI 0 – I ao2Ra

3. Armature resistance, Ra = V / I a

MOTOR ACTION:

1. Load current = IL

2. Armature current , I a = IL – I f

3. Armature Copper loss = I a2Ra

4. Total losses = Wc + I a2Ra

5. Input = V I

6. Output = Input – Losses

7. Efficiency, = (Output / Input) x 100

GENERATOR ACTION:

1. Armature Current I a = IL + I f

2. Armature Copper loss = I a2 R a

3. Total losses = W c + I a2 R a

4. Output = V I

5. Input = Output + Losses

6. Efficiency, = (Output / Input) x 100

PROCEDURE:

NO LOAD TEST:

1. Note the name plate details of the machine.

2. The connections are made as per circuit diagram.

3. Close the DPST switch.

4. Start the motor by using three-point starter.

5. Adjust the speed to rated speed by increasing field circuit resistance (Field rheostat).

6. Enter the input voltage, No load current and field current in Table (1).

TO FIND Ra:

1. The connections are made as per circuit diagram shown in diagram.

2. Close the DPST switch and increase the load step by step.



30

TABLE (3): CALCULATION OF EFFICIENCY AS A MOTOR:

Constant Loss: Calculated value from Table (1)

TABLE (4): CALCULATION OF EFFICIENCY AS A GENERATOR:

S.

No Load Current

I

(Amps)

Armature

Current

Ia = I - I f (Amps)

Armature

Copper loss

= I a2 R a

(Watts)

Total Losses

= Wo+ I a2 R a

(Watts)

Input

V I

(Watts)

Output =

Input – losses

(Watts)

Efficiency

=(output/

input)x100

(Percentage)

1. ¼ th of

rated value

2. ½ th of

rated value

3. ¾ th of

rated value

4. Rated value

S.

No

Load

Current

I

(Amps)

Armature

Current

Ia = I + I f (Amps)

Armature

Copper loss

= I a2 R a

(Watts)

Total Losses

= Wo+ I a2 R a

(Watts)

Output

V I

(Watts)

Input =

Output + Losses

(Watts)

Efficiency

=(output/

Input)x100

(Percentage)

1. ¼ th of

rated value

2. ½ th of

rated value

3. ¾ th of

rated value

4. Rated value


31

MODEL GRAPH:

MODEL CALCULATION:


32


33

RESULT:

VIVA QUESTION:

1. What is the function of no-volt release coil in 3point starters?

2. How to change the direction of rotation of d.c motor?

3. Swinburne‘s test is also called?

4. List the various losses in d.c machine.

5. Name the various methods of testing the d.c machine.


34

CIRCUIT DIAGRAM FOR SPEED CONTROL OF DC SHUNT MOTOR

FUSE RATING


NAME PLATE DETAILS


35

SPEED CONTROL OF DC SHUNT MOTOR

AIM:

To control the speed of the given DC shunt motor by field and armature control methods

and also to draw their characteristics curves.

APPARATUS REQUIRED:

S. No APPARATUS TYPE RANGE QUANTITY

1 Ammeter MC (0-2) A 1

2 Voltmeter MC (0-300) V 1


4 Rheostat Wire Wound 400 Ω/ 1.1 A 1

5 Rheostat Wire wound 50 Ω/ 5 A 1

6 Connecting Wires - -- As Req

FUSE RATING:


PRECAUTIONS:

All connections should be perfectly tight and no loose wire should lie on the work table.

There should be no load on the motor at the time of starting.

At the time of starting, the field circuit rheostat is in minimum resistance position and

armature rheostat is in maximum position.

Hold the tachometer with both hands steady and in line with the motor shaft so that it

reads correctly.


36

TABLE 1: FIELD CONTROL METHOD.

Rated Speed:

TABLE 2: ARMATURE CONTROL METHOD

Rated Speed:

S.NO.

Armature Voltage (Va)=

Speed (N)

(Rpm)

Field Current (If)

(Amps)

S.NO

Field Current(If)=

Speed (N)

(Rpm)

Armature Voltage

(Va)

(Volts)


37

PROCEDURE:

Field current (or) flux control method:

1. Note down the name plate details of the motor.

2. Connections are made as per circuit diagram.

3. The motor run at rated speed by adjusting the armature and field rheostat.

4. Keep the armature voltage constant at rated value.

5. Increase the speed in steps of 50 rpm above the rated speed using field rheostat and note

down the corresponding field current values in Table (1).

Armature (or) voltage control method:

1. Note down the name plate details of the motor.

2. Connections are made as per circuit diagram.

3. The motor run at rated speed by adjusting the armature and field rheostat.

4. Keep the field current constant at rated speed.

5. Decrease the speed in steps of 50 rpm below the rated speed using armature rheostat

and note down the corresponding field current values in Table (2).


38

MODEL GRAPH:

Armature Control Method Field Control Method

MODEL CALCULATION:


39

RESULT:

VIVA QUESTION:

1. What are the limitations of armature voltage control and field current control methods?

2. Why both rheostats are kept at minimum resistance position in the starting condition?

3. What is starter? Why is it required?

4. What are the applications of dc shunt motor?

5. Why brushes are made from carbon?

6. Why is thin conductor used for field winding? & thick conductor for armature winding?


40

CIRCUIT DIAGRAM FOR LOAD TEST ON SINGLE PHASE TRANSFORMER

FUSE RATING


NAME PLATE DETAILS


41

LOAD TEST ON SINGLE PHASE TRANSFORMER

AIM:

To conduct the load test on a given single phase transformer and draw its performance

curves.

APPARATUS REQUIRED:


1 Ammeter MI

(0-5)A 1

(0-10)A 1

2 Voltmeter MI (0-300)V 1

(0-150)V 1

3 Wattmeter UPF 300V,5A 1

4 1φ auto transformer 230/(0-270)V 1

5 1φ step down transformer 230/110V,1KVA 1

6 Loading Rheostat Wire Wound 1

7 Tachometer Digital 1

8 Connecting wires - - As required

9 DPST - - 1

FUSE RATING:

Primary Current = KVA Rating of the Transformer / Primary Voltage.

Secondary Current = KVA Rating of the Transformer / Secondary Voltage.

110-125% of Primary current (fuse rating for primary side).

110-125% of Secondary current (fuse rating for secondary side).

PRECAUTIONS:

At the time of starting, the DPST switch on secondary side should be kept in open

condition.

At the time of starting, there should be no load on the loading rheostat.


42

Table: Load Test on Single Phase Transformer.

Multiplication Factor =


43

FORMULAE:

1. Output power = Vs x Is x CosΦ in Watts.

Where,

Vs – Secondary voltage in volts.

Is – secondary current in amps.

Cos Φ - power factor.

2. Input Power = Wattmeter reading in Watts.

3. Efficiency = (output power/Input power) X 100 %

4. Voltage Regulation = [(V no load - V load) / (V load)] X100 %

Where,

V no load – no load voltage in volts.

V load – load voltage in volts.

PROCEDURE:


2. The SPST Switch on the Primary side is closed and the DPST Switch on the Secondary

side is opened.

3. The Autotransformer is adjusted to energize the transformer with rated Primary

Voltage.

4. The Volt meters and Ammeters Readings are noted and tabulated at No load condition.

5. The DPST switch on the secondary side is closed.

6. The transformer is loaded up to 130% of the Rated Load, corresponding Ammeters,

Voltmeters and Wattmeter readings are noted and tabulated.

7. After the observation of all the readings the load is released gradually to its initial

position.

8. The Autotransformer is brought to its initial position.

9. The Supply is switched off.


44

MODEL GRAPH:

MODEL CALCULATION:


45

RESULT:

VIVA QUESTIONS:


46

CIRCUIT DIAGRAM FOR OPEN CIRCUIT TEST ON SINGLE PHASE TRANSFORMER

Tabulation for OC test on Single phase transformer



47

OPEN CIRCUIT TEST AND SHORT CIRCUIT TEST

ON SINGLE PHASE TRANSFORMER

AIM:

To Predetermine the Efficiency and Regulation on a given single phase

transformer by conducting the Open Circuit test and Short Circuit test and also draw its

Equivalent circuit.

APPARATUS REQUIRED:


1 Ammeter MI (0-1)A, (0-5A)

(0-10A)

Each 1


(0-150)V 1

3 Wattmeter LPF

UPF

150V,1A

150V,5A

Each 1


4 1φ Taping transformer 230/110V,1KVA 1



FUSE RATING:

Primary Current = KVA Rating of the Transformer / Primary Voltage.

Secondary Current = KVA Rating of the Transformer / Secondary Voltage.

110-125% of Primary current (fuse rating for primary side).

110-125% of Secondary current (fuse rating for secondary side).

PRECAUTIONS:

At the time of starting, the auto transformer should be in the minimum voltage

position.

For O.C test, the HV side of the transformer is in open circuit condition.

For S.C test, the LV side of the transformer is short circuited.


48

CIRCUIT DIAGRAM FOR SHORT CIRCUIT TEST ON SINGLE PHASE TRANSFORMER

Tabulation for SC test on Single phase transformer



49

FORMULAE USED:

O.C Test:

1. No load Power factor, Cos Φo = [ Woc / ( Voc x I oc ) ]

Where, Woc – No load losses.

Voc – No load voltage.

I oc – No load current.

2. Magnetizing component, Im = I oc x Sin Φo

3. Working component, Iw = I oc x Cos Φo

4. No load resistance, R 0 = V oc / Iw in ohms

5. No load reactance, X 0 = V oc / Im in ohms

S.C Test.

1. Primary winding resistance, R1 = Wsc / Isc2 in ohms

Where, Wsc - Short circuit power in Watts

Isc - Short circuit current in Amps

2. Primary winding impedance, Z1 = Vsc / Isc in ohms

where, V sc = Short circuit voltage in Volts

3. Primary winding reactance, X1 = Z12 - R1

2 in ohms

4. Secondary winding resistance, R 2 = W sc / I sc2 in ohms

5. Secondary winding impedance , Z 2 = V sc / I sc in ohms

6. Secondary winding reactance , X2 = Z 22 – R2

2 in ohms

7. Transformation ratio ( K ) = V 2 / V 1

8. Equivalent secondary resistance referred to primary side,

R2 ‘ = R2 / K 2 in ohms.

9. Equivalent secondary reactance referred to primary side,

X2 ‘ = X2 / K 2 in ohms.


50

TO CALCULATE THE EFFICIENCY:

Iron loss (Wi): Calculated from Table (1)

Short Circuit loss (Wsc): Calculated from Table (2)

S.NO LOAD

FRACTION

X

IRON

LOSS

Wi

(Watts)

COPPER

LOSS

X2 WSC

(Watts)

TOTAL

LOSS

W

(Watts)

OUTPUT

POWER

PO

(Watts)

INPUT

POWER

Pi

(Watts)

EFFICIENCY

η

(%)

UPF PF=0.8 UPF PF=0.8 UPF PF=0.8

1 0.25

2 0.5

3 0.75

4 1.00

5 1.25


51

EFFICIENCY:

1. Iron loss, wi = woc in Watts.

Where, Woc - No load loss.

2. Copper loss, Wc - x2 WSC in Watts.

Where, x - Fraction of load.

WSC - Short circuit losses.

3. Total loss, W = Wi + Wc in Watts.

4. Output power, Po = x X kVA X Cos Φ

5. Where,

Cos Φ – power factor.

Cos Φ= 1 for UPF.

Cos Φ= 0.8 for LPF.

6. Input power, Pi = Po+ W in Watts.

7. Efficiency, η = (Po / Pi) X 100 %

REGULATION:

1. Percentage Regulation

= [x Isc / VOC ( R01 Cos Φ ± X01 Sin Φ ) ] x 100 %

+ Lagging Leading

2. Total resistance as referred to primary side, R01= R1 + R2 ‘in ohms.

3. Total reactance as referred to primary side, X01 = X1+ X2 ‘in ohms.


52

Resultant Tabulation to find out the Efficiency: Core (Or) Iron Loss = A Rating of Transformer =

Rated Short Circuit Current (ISC) = Short Circuit Power (WSC) =

Resultant Tabulation to find out the Regulation:

POWERFACTOR

COS Φ

125% LOAD, X = 1.25 100% LOAD, X = 1 75% LOAD, X = 0.75

LAG LEAD LAG LEAD LAG LEAD

0.2

0.4

0.6

0.8

1


53

PROCEDURE:

OPEN CIRCUIT TEST:


2. The SPST Switch on the Primary side is closed.

3. The Autotransformer is adjusted to Energize the transformer with rated Primary

Voltage on the LV side

4. The Volt meter, Watt meter and Ammeter Readings are noted at No load condition

5. The Autotransformer is brought to its initial position


SHORT CIRCUIT TEST:


2. The SPST Switch on the Primary side is closed

3. The Autotransformer is adjusted to energize the transformer with rated Primary Current

on the HV side.

4. The Voltmeter, Wattmeter and Ammeter Readings are noted down at short circuit

condition.

5. The Autotransformer is brought to its initial position



54

EQUIVALENT CIRCUIT FOR SINGLE PHASE TRANSFORMER

MODEL GRAPH:

MODEL CALCULATION:


55

RESULT:

VIVA QUESTIONS:


56

CIRCUIT DIAGRAM FOR LOAD TEST ON SINGLE PHASE INDUCTION MOTOR

FUSE RATING


NAME PLATE DETAILS


57

LOAD TEST ON SINGLE PHASE INDUCTION MOTOR

AIM:

To determine the performance characteristic of a given single phase capacitor start

induction motor by conducting load test.

APPARATUS REQUIRED:

FUSE RATING:

Fuse rating = 125% of rated current.

PRECAUTION:

Before switching on the supply the single phase auto transformer is kept in minimum

position.

Initially these should be on no load while starting the motor.

FORMULA USED:

1. Torque, T = (S1~S2)*9.81*R N.m.

2. Output power = 2π NT/60*W

3. Effecting (η%) = 0/P Power/I/p Power*100

4. Slip (%S) = NS – N/NS*100

5. Power factor = Cos φ=W/VI

PROCEDURE:


2. Switch on the supply at no load condition.

3. Apply the rated voltage to the motor using the single phase auto transformer and note

down the readings at ammeter and wattmeter.

4. Vary the load in suitable steps and note down all the meter readings till full load

condition.

SL. NO APPARATUS RANGE TYPE QUANTITY 1 Voltmeter (0-300) V MI 1

2 Ammeter (0-20) A MI 1

3 Wattmeter 300 V, 20 A UPF 1

4 Tachometer - Digital 1

5 1φ auto transformer 230V/0-270V 1

6 Connecting wires - - As Req.


58

TABLULATION: M.F =

MODEL CALCULATION:

Sl.No.

VL

(V)

IL

(A)

Speed(N)

(Rpm)

S1

(Kg)

S2

(Kg)

S1 ~ S2

(Kg)

Torque

(N-m)

Wattmeter Reading Output

Power

(W)

Eff

icie

ncy

η

%

PF

= c

osΦ

% S

lip

Obs.

(W)

Actual

(W)


59


60

MODEL GRAPH:

ELECTRICAL CHARACTERISTICS:

MECHANICAL CHARACTERISTICS:


61

RESULT:

VIVA QUESTIONS:


62

CIRCUIT DIAGRAM FOR NO LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR

FUSE RATING


NAME PLATE DETAILS


63

EQUIVALENT CIRCUIT OF THREE PHASE SQUIRREL

CAGE INDUCTION MOTOR AIM:

To conduct a No Load test and Blocked Rotor test on three phase squirrel cage induction

motor and to draw the equivalent circuit.

APPARATUS REQUIRED:


1 Ammeter MI (0-5A),

(0-10A)

Each 1


3 Wattmeter UPF,LPF 600V,5A

150V,10A

Each 1




FUSE RATING:

No Load: 10 % of rated current (Full load current).

Load: 110-125 % of rated current (Full load current).

PRECAUTION:

The autotransformer should be kept at minimum voltage position.


64

CIRCUIT DIAGRAM FOR BLOCKED ROTOR TEST ON THREE PHASE SQUIRREL CAGE

INDUCTION MOTOR (Equivalent circuit)


65

FORMULAE USED:

OC TEST:

1. No load power factor (Cos φ 0) = P0/V0I0

V0 - No load voltage per phase in volts.

I0 - No load current per phase in amps.

P0 - No load power per phase in watts.

2. Working component current (Iw) = I0 (ph) X Cos φ 0

3. Magnetizing current (Im) = I0 (ph) X Sin φ 0

4. No load resistance (R0) =V0/I0 (ph) Cos φ 0 in W.

5. No load reactance (X0) = V0/I0 (ph) Sin φ 0 in W.

SC TEST:

1. Motor equivalent Impedance referred to stator (Zsc(ph)) = Vsc(ph) / Isc(ph) in Ω.

2. Motor equivalent Resistance referred to stator (Rsc(ph)) = Psc(ph) / I2sc(ph) in Ω.

3. Motor equivalent Reactance referred to stator (Xsc(ph)) = √(Z sc(ph)2- Rsc(ph)2) in Ω.

4. Rotor Resistance referred to stator (R2’(ph)) = Rsc(ph) – R1 in Ω.

5. Rotor Reactance referred to stator (X2’(ph)) = Xsc(ph) / 2 = X1 in Ω.

Where, R1 - stator resistance per phase.

X1 – stator reactance per chapter.

R1 = R(ac) =1.6 x R(dc).

6. Equivalent load resistance (RL’) = R2’ (1/s – 1) in Ω.

Where, Slip (S) = (Ns-Nr) / Ns.

Ns – Synchronous speed in rpm.

Nr – Rotor speed in rpm.


66

TABULATION FOR NO LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR Speed of the Induction motor:

Type of the Stator connection:

Multiplication Factor:

TABULATION FOR BLOCKED ROTOR TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR Type of the Stator connection:



67

PROCEDURE:


2. For No-Load or open circuit test by adjusting autotransformer, apply rated voltage and

Note down the voltmeter, ammeter and wattmeter readings. In this test rotor is free to

rotate.

3. For short circuit or blocked rotor test by adjusting autotransformer, apply rated current

and note down the voltmeter ,ammeter and wattmeter readings. In this test rotor is

blocked.

4. After that make the connection to measure the stator resistance as per the circuit

diagram.

5. By adding the load through the loading rheostat note down the ammeter, voltmeter

reading for various values of load.


68

EQUIVALENT CIRCUIT FOR THREE PHASE SQUIRREL CAGE

INDUCTION MOTOR

MODEL CALCULATION:


69

RESULT:

VIVAQUESTION:


70

CIRCUIT DIAGRAM FOR LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR

FUSE RATING


NAME PLATE DETAILS


71

LOAD TEST ON THREE PHASE SQUIRREL CAGE

INDUCTION MOTOR

AIM:

To conduct a load test on a three phase squirrel cage induction motor and to draw the

performance characteristic curves.

APPARATUS REQUIRED:

FUSE RATING:

110-125% of rated current (Full load current).

PRECAUTIONS:

There should be no load on the motor at the time of starting.

FORMULAE USED:

1. Torque = (S1-S2) (R+t/2) x 9.81 N-m

Where, S1, S2 – spring balance readings in Kg.

R - Radius of brake drum in m.

t - Thickness of belt in m.

Output Power = 2 PNT/60 watts.

N- Rotor speed in rpm.

T- Torque in N-m.

2. Input Power = (W1+W2) Watts.

W1, W2 – Wattmeter readings in Watts.

3. Percentage of Efficiency = (Output Power/ Input Power) x 100%.


1 Ammeter MI (0-5/10)A 1


3 Wattmeter UPF 600V,5/10A 2

4 Tachometer Digital 1



72

TABULATION FOR LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR.



73

4. Percentage of Slip = (NS-Nr)/Ns x 100%

Ns-Synchronous speed in rpm.

Nr-Rotor speed in rpm.

5. Power factor = (W1+W2)/ √ 3 VLIL.

PROCEDURE:


2. The TPSTS is closed and the motor is started using On Line starter to run at rated speed.

3. At no load the speed, current, voltage and power are noted down.

4. By applying the load for various values of current the above-mentioned readings are

noted.

5. The load is later released and the motor is switched off and the graph is drawn.


74

MODEL GRAPHS:

Mechanical Characteristics Electrical Characteristics

MODEL CALCULATION:


75

RESULT:

VIVA QUESTION:

269010454 electrical-machines-lab-manual-for-petrochemaical

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