electrical engg cse

7/31/2019 Electrical Engg CSE

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Chennai Institute of Technology

1 Faculty name: G.Keerthi Vijayadhasan Dept:EEE

CHENNAI INSTITUTE OF TECHNOLOGY

Kundrathur to Sriperumbudur Highway, Kundrathur,Nandhambakkam Post, Pudupedu,

Chennai 600 069.

(www.citchennai.net)

Department of Computer Science and Engineering

III Semester

Lab Manual

1.2.

3.Name

Roll No

Reg.No

Year

Branch


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DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

LABORATORY MANUAL

Subject Name: ELECTRICAL ENGINEERING LABSubject Code : 131354Semester : III


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ELECTRICAL ENGINEERING

LIST OF EXPERIMENTS:

1. Load test on DC Shunt & DC Series motor

2. O.C.C & Load characteristics of DC Shunt and DC Series generator3. Speed control of DC shunt motor (Armature, Field control)4. Load test on single phase transformer5. O.C & S.C Test on a single phase transformer6. Regulation of an alternator by EMF & MMF methods.7. V curves and inverted V curves of synchronous Motor8. Load test on three phase squirrel cage Induction motor9. Speed control of three phase slip ring Induction Motor10. Load test on single phase Induction Motor.11. Study of DC & AC Starters


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Ex.No:DATE:

LOAD TEST ON DC SHUNT MOTOR

AIM:

To conduct a load test on DC shunt motor and to find its efficiency

APPARATUS REQUIRED:

S.No. Apparatus Range Type Quantity

1 Ammeter (0-20)A MC 1

2 Voltmeter (0-300)V MC 1

3 Rheostat 1250, 0.8A Wire Wound 1

4 Tachometer (0-1500) rpm Digital 1

5 Connecting Wires 2.5sq.mm. Copper Few

PRECAUTIONS:

1. DC shunt motor should be started and stopped under no load condition.

2. Field rheostat should be kept in the minimum position.3. Brake drum should be cooled with water when it is under load.

PROCEDURE:

1. Connections are made as per the circuit diagram.


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TABULAR COLUMN:

S.No.

Voltage

V

(Volts)

Current

I

(Amps)

Spring Balance

Readings(S1 S2)Kg

Speed

N

(rpm)

Torque

T

(Nm)

Output

Power

Pm

(Watts)

Input

Power

Pi

(Watts)

Efficiency

%S1(Kg) S2(Kg)


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Circumference of the Brake drum = cm.

2. After checking the no load condition, and minimum field rheostat position, DPST switch is closed and starter resistance is gradually

removed.

3. The motor is brought to its rated speed by adjusting the field rheostat.

4. Ammeter, Voltmeter readings, speed and spring balance readings are noted under no load condition.

5. The load is then added to the motor gradually and for each load, voltmeter, ammeter, spring balance readings and speed of the motor arenoted.

The motor is then brought to no load condition and field rheostat to minimum position, then DPST switch is opened

FORMULAE:

CircumferenceR = ------------------- m Torque T = (S1 S2) x R x 9.81 Nm

100 x2 Input Power Pi = VI Watts2NT

Output Power Pm = ------------ Watts60

Output Power

Efficiency % = -------------------- x 100%Input Power


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MODEL GRAPHS:

MODEL CALCULATION:

SpeedN(rpm)

y

x

Torque T (Nm)

Speed

N(rpm)

TorqueT(Nm)

Efficie

ncy%

N

T

y3 y2 y1

Out ut Power Watts


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RESULT: Thus the load test on DC shunt motor is conducted and its efficiency is determined.


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Ex.No:

DATE: LOAD TEST ON DC SERIES MOTOR

AIM:

To conduct a load test on DC Series Motor and to find its efficiency

APPARATUS REQUIRED:




3 Tachometer(0-3000)

rpmDigital 1


PRECAUTIONS:

1. The motor should be started and stopped with load

2. Brake drum should be cooled with water when it is under load.

PROCEDURE:


2. After checking the load condition, DPST switch is closed and starter resistance is gradually removed.

3. For various loads, Voltmeter, Ammeter readings, speed and spring balance readings are noted.

4. After bringing the load to initial position, DPST switch is opened.

TABULAR COLUMN:


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S.No.

Voltage

V

(Volts)

Current

I

(Amps)

Spring BalanceReadings

(S1 S2)KgSpeed

N

(rpm)

Torque

T

(Nm)

OutputPower

Pm

(Watts)

InputPower

Pi

(Watts)

Efficiency

%S1(Kg) S2(Kg)

Circumference of the Brake drum = cm.

FORMULAE:


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Circumference

R = ------------------- m100 x2

Torque T = (S1 S2) x R x 9.81 Nm

Input Power Pi = VI Watts

2NTOutput Power Pm = ------------ Watts

60

Output Power

Efficiency % = -------------------- x 100%

Input Power

MODEL GRAPH:

eT

Nm

N

rm

nc%

y3 y2 y1

T


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MODEL CALCULATION:


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RESULT: Thus the load test on DC series motor is conducted and its efficiency is determined.


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Department of EEE, Chennai Institute of Engineering, Kundrathur


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Ex.No:

DATE:OPEN CIRCUIT AND LOAD CHARACTERISTICS OF SELF EXCITED

DC SHUNT GENERATOR

AIM:

To obtain open circuit characteristics of self excited DC shunt generator and to find its critical resistance

APPARATUS REQUIRED:




3 Rheostats 1250, 0.8A Wire Wound 2

4 SPST Switch - - 1

5 Tachometer (0-1500)rpm Digital 1


PRECAUTIONS:

1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine.

2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine.

3. SPST switch is kept open during starting and stopping.


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TABULAR COLUMN:

S.N

o.

Field

Current

If (Amps)

Armature

Voltage

Eo (Volts)

MODEL GRAPH:

Eo

If

Critical Resistance = Eo / IfOhmsEo(Volts)

If(Amps)


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For open circuit:

PROCEDURE:


2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat, DPST switch is closed and

starting resistance is gradually removed.

3. By adjusting the field rheostat, the motor is brought to rated speed.

4. Voltmeter and ammeter readings are taken when the SPST switch is kept open.

5. After closing the SPST switch, by varying the generator field rheostat, voltmeter and ammeter readings are taken.

6. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, SPST switch is opened and

DPST switch is opened.

For load test:

PROCEDURE:


2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST

switch is closed and starting resistance is gradually removed.

3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field

rheostat of generator.

4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted.5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of

DC shunt motor to minimum position, DPST switch is opened.


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DETERMINATION OF ARMATURE RESISTANCE:

PROCEDURE:


2. Supply is given by closing the DPST switch.

3. Readings of Ammeter and Voltmeter are noted.

4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I

D

P

S

T

S

W

I

T

C

H

+

-

-+

(0-300)VMC

(0-20)A

MC

Fuse

Fuse

A1

A2

27A

27A

LOAD

5 KW, 230V

G

A

V220V

DC

Supply

+

-


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TABULAR COLUMN:

S.No. Voltage

V (Volts)

Current

I (Amps)

Armature Resistance

Ra (Ohms)

TABULAR COLUMN:

S.No.

Field

CurrentIf (Amps)

Load

CurrentIL (Amps)

Terminal

Voltage(V) Volts

Ia = IL + If

(Amps) Eg =V + Ia Ra

(Volts)


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FORMULAE:

Eg = V + Ia Ra (Volts)

Ia = IL + If (Amps)

Eg : Generated emf in Volts

V : Terminal Voltage in Volts

Ia : Armature Current in Amps

IL : Line Current in Amps

If : Field Current in Amps

Ra : Armature Resistance in Ohms


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MODEL GRAPH:

MODEL CALCULATION:

VL,E

Volts

If, IL (Amps)

V Vs IL

(Ext Char)

E Vs IL

(Int Char)


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RESULT:

Thus the open circuit and load characteristic of self excited DC shunt generator is obtained.


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Ex.No:

DATE:

OPEN CIRCUIT CHARACTERISTICS OF SEPARATELY EXCITED DC SHUNT GENERATOR

AIM:

To obtain open circuit characteristics of separately excited DC shunt generator.

APPARATUS REQUIRED:




3 Rheostats 1250, 0.8A Wire Wound 2

4 Tachometer (0-1500)rpm Digital 1


PRECAUTIONS:

1. The field rheostat of motor should be in minimum resistance position at the time of starting and stopping the machine.

2. The field rheostat of generator should be in maximum resistance position at the time of starting and stopping the machine.


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Eo(Volts)

If(Amps)

TABULAR COLUMN:

MODEL GRAPH:

S.No.Field Current

If (Amps)

Armature Voltage

Eo (Volts)


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For open circuit:

PROCEDURE:


2. After checking minimum position of motor field rheostat, maximum position of generator field rheostat,

DPST switch is closed and starting resistance is gradually removed.

3. By adjusting the field rheostat, the motor is brought to rated speed.

4. By varying the generator field rheostat, voltmeter and ammeter readings are taken.

5. After bringing the generator rheostat to maximum position, field rheostat of motor to minimum position, DPST switch is opened.

For load test:

PROCEDURE:


2. After checking minimum position of DC shunt motor field rheostat and maximum position of DC shunt generator field rheostat, DPST

switch is closed and starting resistance is gradually removed.

3. Under no load condition, Ammeter and Voltmeter readings are noted, after bringing the voltage to rated voltage by adjusting the field

rheostat of generator.

4. Load is varied gradually and for each load, voltmeter and ammeter readings are noted.

5. Then the generator is unloaded and the field rheostat of DC shunt generator is brought to maximum position and the field rheostat of

DC shunt motor to minimum position, DPST switch is opened.


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DETERMINATION OF ARMATURE RESISTANCE:

MODEL GRAPH:

D

P

S

T

S

WI

TC

H

+

-

-+

(0-300)V

MC

(0-20)A

MC

Fuse

Fuse

A1

A2

27A

27A

LOAD

5 KW, 230V

G

A

V220V

DC

Supply

+

-

V

L,E

Volts

If, IL (Amps)

V Vs IL

(Ext Char)

E Vs IL

(Int Char)


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PROCEDURE:


2. Supply is given by closing the DPST switch.

3. Readings of Ammeter and Voltmeter are noted.

4. Armature resistance in Ohms is calculated as Ra = (Vx1.5) /I

FORMULAE:

Eg = V + Ia Ra (Volts)Ia = IL + If (Amps)

Eg : Generated emf in Volts

V : Terminal Voltage in Volts

Ia : Armature Current in Amps

IL : Line Current in Amps

If : Field Current in Amps

Ra

: Armature Resistance in Ohms


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TABULAR COLUMN:

S.No. Voltage

V (Volts)

Current

I (Amps)

Armature Resistance

Ra (Ohms)

TABULAR COLUMN:

S.No.

Field

CurrentIf (Amps)

Load

CurrentIL (Amps)

Terminal

Voltage(V) Volts

Ia = IL + If

(Amps) Eg =V + Ia Ra(Volts)


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RESULT:

Thus the open circuit and load characteristics of separately excited DC shunt generator are obtained.


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Ex.No: SPEED CONTROL OF DC SHUNT MOTOR

DATE:

AIM:

To obtain speed control of DC shunt motor by

a. Varying armature voltage with field current constant.

b. Varying field current with armature voltage constant

APPARATUS REQUIRED:


1 Ammeter (0-20) A MC 1

2 Voltmeter (0-300) V MC 1

3 Rheostats 1250, 0.8A50, 3.5A

WireWound

Each 1

4 Tachometer (0-3000) rpm Digital 1


PRECAUTIONS:

1. Field Rheostat should be kept in the minimum resistance position at the time of starting and stopping the motor.

2. Armature Rheostat should be kept in the maximum resistance position at the time of starting and stopping the motor.


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TABULAR COLUMN:

(i) Armature Voltage Control:

S.No.

If1 = If2 = If3 =

Armature

Voltage

Va ( Volts)

Speed

N (rpm)

Armature

Voltage

Va ( Volts)

Speed

N (rpm)

Armature

Voltage

Va ( Volts)

Speed

N (rpm)

(ii) Field Control:

S.No.

Va1 = Va2 = Va3 =

Field

Current

If (A)

Speed

N (rpm)

Field

Current

If (A)

Speed

N (rpm)

Field

Current

If (A)

Speed

N (rpm)


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PROCEDURE:


2. After checking the maximum position of armature rheostat and minimum position of field rheostat, DPST switch is closed

(i) Armature Control:

1. Field current is fixed to various values and for each fixed value, by varying the armature rheostat, speed is noted for various voltages

across the armature.(ii)Field Control:

1. Armature voltage is fixed to various values and for each fixed value, by adjusting the field rheostat, speed is noted for various field

currents.

2. Bringing field rheostat to minimum position and armature rheostat to maximum position DPST switch is opened.


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MODEL GRAPHS:

SpeedN(rpm)

SpeedN(rpm)

If(Amps)Va (Volts)

If1

If3

If2

Va3

Va1

Va2


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RESULT:

Thus the speed control of DC Shunt Motor is obtained using Armature and Field control methods.


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Ex.No:

DATE: LOAD TEST ON A SINGLE PHASE TRANSFORMER

AIM:

To conduct a load test on single phase transformer to find its efficiency and percentage regulation

APPARATUS REQUIRED:


1 Ammeter(0-10)A

(0-5) A

MI

MI

1

1

2 Voltmeter(0-150)V

(0-300) V

MI

MI

1

1

3 Wattmeter(300V, 5A)

(150V, 5A)

Upf

Upf

1

1

4 Auto Transformer 1, (0-260)V - 1

5 Resistive Load 5KW, 230V - 1

6 Connecting Wires 2.5sq.mm Copper Few


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TABULAR COLUMN:

Load

Primary Secondary Input

Power

W1 x

MF

Output

Power

W2 x

MF

Efficiency

%

%

RegulationV1(V)

I1

(A)

W1

(W)

V2(V)

I2

(A)

W2

(W)


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PRECAUTIONS:

1. Auto Transformer should be in minimum position.

2. The AC supply is given and removed from the transformer under no load condition.

PROCEDURE:


2. After checking the no load condition, minimum position of auto transformer and DPST switch is closed.

3. Ammeter, Voltmeter and Wattmeter readings on both primary side and secondary side are noted.

4. The load is increased and for each load, Voltmeter, Ammeter and Wattmeter readings on both primary and secondary sides are

noted.

5. Again no load condition is obtained and DPST switch is opened.

FORMULAE:

Output Power = W2 x Multiplication factor

Input Power = W1 x Multiplication factor

Output PowerEfficiency % = -------------------- x 100%

Input PowerVNL - VFL (Secondary)

Regulation R % = ------------------------------ x 100%VNL


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MODEL GRAPHS:

MODEL CALCULATION:

Efficienc

%

RegulationR%

R

Output Power (Watts)


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RESULT:

Thus the load test on single phase transformer is conducted to determine its efficiency.


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Ex.No:

DATE:

OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER

AIM:

To predetermine the efficiency and regulation of a transformer by conducting open circuit test and short circuit test and to draw

equivalent circuit

APPARATUS REQUIRED:


1 Ammeter(0-2)A

(0-5) A

MI

MI

1

1

2 Voltmeter (0-150)V MI 2

3 Wattmeter(150V, 5A)

(150V, 5A)

LPF

UPF

1

1

4 Connecting Wires 2.5sq.mm Copper Few

PRECAUTIONS:

1. Auto Transformer should be in minimum voltage position at the time of closing & opening DPST Switch.


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PROCEDURE:

OPEN CIRCUIT TEST:


2. After checking the minimum position of Autotransformer, DPST switch is closed.

3. Auto transformer variac is adjusted get the rated primary voltage.

4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.

5. Auto transformer is again brought to minimum position and DPST switch is opened.

SHORT CIRCUIT TEST:


2. After checking the minimum position of Autotransformer, DPST switch is closed.

3. Auto transformer variac is adjusted get the rated primary current.

4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.

5. Auto transformer is again brought to minimum position and DPST switch is opened.


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TABULAR COLUMN:

SHORT CIRCUIT TEST:

Vs/c

(Volts)

Is/c

(Amps)

Ws/c

(Watts)

TABULAR COLUMN:

OPEN CIRCUIT TEST:

Vo/c

(Volts)

Io/c

(Amps)

Wo/c

(Watts)


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FORMULAE:

Core loss: Wo = VoIo cos o

Wo Wo

cos o = ------- o = cos-1 -------

Vo Io Vo Io

I = Io cos o (Amps) I = Io sin o (Amps)

Percentage Efficiency: for all loads and p.f.Output Power (X) x KVA rating x 1000 x cos

Efficiency % = -------------------- = ------------------------------------------------Input Power Output power + losses

V0

Ro = ------- I

V0

Xo = ------- I

Wsc

Ro2 = ------- Isc

2

Vsc

Zo2 = ------- Isc

Xo2 = (Zo2 - Ro22)1/2

R02

Ro1 = ------- K

2

X02

Xo1 = ------- K

2

V2

K= ------- = 2

V1


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EQUIVALENT CIRCUIT:

MODEL GRAPHS:

ZL = ZL/K2

Efficienc

%

Output power (Watts)

Xo1Ro1

Ro Xo

Vo

Io

ISCo

R

N

L

O

A

D

w

%

%

Percentage Regulation:


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Percentage Regulation:

(X) x Isc (Ro2 cos Xo2sin ) x 100

R% = --------------------------------------

V2

(X) x KVA rating x 1000 x cos

Where X is the load and it is 1 for full load, for half load, load, load etc.. and the power factor is, upf, o.8 p.f lag and 0.8 p.f lead

RESULT:

Thus the efficiency and regulation of a transformer is predetermined by conducting open circuit test and short circuit test and the

equivalent circuit is drawn.

.

+ = lagging

- = leading


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EX.NO:

DATE: REGULATION OF 3PHASE ALTERNATOR BY EMF AND MMF METHODS

AIM:

To predetermine the regulation of 3-phase alternator by EMF and MMF methods and also draw the vector diagrams.

APPARATURS REQUIRED:

SL.NO Name of the Apparatus Type Range Quantity

1 Ammeter MC 0 1/2 A 1

2 Ammeter MI 0 5/10 A 1

3 Voltmeter MC 0 10 V 1

4 Voltmeter MI 0 600 V 1

5 Rheostat Wire

wound

250 , 1.5 A 1

6 Rheostat Wire

wound

1200, 0.8 A 1

7 Tachometer Digital --- 1

8 TPST knife switch -- -- 1

REGULATION OF 3-PHASE ALTERNATOR BY EMF AND MMF METHODS


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REGULATION OF 3 PHASE ALTERNATOR BY EMF AND MMF METHODS

TABULAR COLUMNS: OPEN CIRCUIT TEST:

S.No.

Field Current (If) Open Circuit Line

Voltage (VoL)

Open circuit Phase

Voltage (Voph)

Amps Volts Volts

THEORY:


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The regulation of a 3-phase alternator may be predetermined by conducting the Open Circuit (OC) and the Sort 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 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.

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 =

2. Synchronous Impedance Zs = O.C. voltage

S.C. current

3. Synchronous Reactance Xs = Zs2 Ra2

4. Open circuit voltage for lagging p.f = (Vcos + IaRa)2 + (Vsin + IaXs)2

5. Open circuit voltage for leading p.f. = (Vcos + IaRa)2 + (Vsin IaXs)2

6. SHORT CIRCUIT TEST:


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S.No. Field Current (If)

Short Circuit Current

(120% to 150% of rated

current) (ISC)

Amps Amps


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7. Open circuit voltage for unity p.f = (V + IaRa)2 + ( IaXs)2

8. Percentage regulation = Eo V x 100

V

EXP.NO: REGULATION OF 3-PHASE ALTERNATOR BY EMF AND MMF METHODS


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TABULAR COLUMNS

EMF METHOD:

SL.NO. Power

factor

Eph (V) % Regulation

Lag Lead Lag Lead

MODEL CALCULATION:


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MMF METHOD:


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MODEL CALCULATION:

SL.NO

.

P.F Vph

(V)

If1

(A)

If2

(A)

Ifr

(A)

Eph (V) % Regulation

Lag Lead Lag Lead Lag Lead


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RESULT:

Thus the regulation of 3-phase alternator has been predetermined by the EMF and MMF methods.

Ci i Di


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Circuit Diagram


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EXP.NO: V AND INVERTED V CURVES OF THREE PHASE SYNCHRONOUS MOTOR

AIM:

To draw the V-Curves and inverted v-curves of the given three phase synchronous motor by constant output.

APPARATUS REQUIRED:

S. No. Name of the Equipment Range Type Qty

THEORY:Refer book and write

PRECAUTIONS:

1. The field rheostat of motor should be in minimum resistance position initially.

2. The field rheostat of alternator should be in maximum resistance position while starting.


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NAME PLATE DETAILS:

PROCEDURE:


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OC Test:

1. Connections are made as per the circuit diagram2. DPST I is closed and the motor is started using a 3 point starter3. The field rheostat of motor is adjusted to give rated speed of alternator.4. DPST 2 is closed and the field rheostat of alternator is adjusted to get

various voltages and corresponding field currents are noted. This procedure isrepeated up to rated field current.

SC Test:1. Connections are made as per the circuit diagram.2. DPST I is closed and the motor is started using a 3 point starter.3. The field rheostat of motor is adjusted to get rated speed of the alternator.4. The field rheostat of alternator is adjusted to get rated current in the armature

of alternator.5. This value of Isc and the corresponding If are noted.6. The field rheostat of alternator is brought back to maximum resistance

Position and the field rheostat of the motor is brought back to minimum

Resistance position.7. Open the DPSTS.

Determination of Ra:1. Connections are made as per the circuit diagram2. DPSTS is closed and the rheostat is adjusted3. For various values of voltages the value of current is noted4. The rheostat is brought back to maximum position

5. DPSTS is opened.

TABULATION:Open Circuit Test


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S.No. No load voltageV0No Load Field CurrentIf

Short Circuit Test:

S.No. Rated I(A) If (A)

SDetermination of Ra:

S.No.Armature Voltage Va Armature Current Ia

Armature ResistanceRa

V A

MODEL CALCULATION:

FORMULAE USED


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FORMULAE USED:

Ra= Rdc* 1.3

Zs= Vph/Isc

Xs= ((Zs2-Ra

2)

=tan-1(Xs/Ra)

Iphcos= P/3VL

SYNCHRONOUS REACTANCE:

OCC and SC characteristic are drawn as shown. The field current OA gives the rated voltage per phase RV. The same field current RAgiven as armature current OB on short circuit.

Therefore Synchronous Impedance, ZS=OV/OBTherefore Synchronous Reactance, XS=ZS2 RS2

CONSTANT INPUT POWER LINE:

Let P be the constant total input to the synchronous motor. Therefore constant input power per phase equals P/3.

Therefore Vph*Iph*cos=P/3Iph* cos=P/3Vph

Since P & V are constant Iph*cos is also a constant.The reference OV1 is drawn to represent V as shown in the figure.The vector OR is equal to Vph/ZS is drawn lagging OV1 by an angle

S N % E it tiE0

(RQ)If

(RG)Ia

(OT)cos


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S.No. % Excitation (RQ) (RG) (OT)=SOT

V A A

MODEL GRAPH:

V Curves.

Where = tan-1(XS/Rac) OS is made equal to Iphcos. At a line STU is drawn perpendicular to the reference vector OV1. This linerepresents the constant input power line.


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CONSTANT EXCITATION CIRCLES:

OR=Vph/Zph represents 100% excitation with R as centre and OR as radius a circle is drawn. This circle is known as 100% excitationcircle. Similarly constant excitation circle cuts the constant input power line at T.

Now OT=Armature Current per phase Ia

Angle SOT = Power factor angle

Similarly other excitation circles determine the armature current and the PF angle at different excitation. The results are tabulated asshown.

Inverted V Curves


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RESULT:

Thus V-curves and inverted V curves of synchronous motor were drawn.


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76/112


EX.NO:


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DATE: LOAD TEST ON 3-PHASE SQUIRREL CAGE INDUCTION MOTOR

AIM:

To draw the performance characteristics of 3-phase squirrel cage induction motor by conducting load test.

APPARATUS REQUIRED:

FUSE RATING;

125% of rated current______A = ____A

THEORY:

A 3-phase induction motor consists of stator and rotor with the other associated parts. In the stator, a 3-phase winding is provided.

The windings of the three phase are displaced in space by 120.A 3-phase current 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.

S.No Name of apparatus Range Type Qty.

1. Ammeter (0-5)A MI 1

2. Voltmeter (0-600)V MI 1

3. Wattmeter (600V,5A) UPF 2

4. Tachometer Digital 1

5. 3- autotransformer 1


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PRECAUTIONS:

1. TPST switch is kept open initially.

2 A t t f i k t t i lt iti


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2. Autotransformer is kept at min. voltage position.

3. There must be no load when starting the load.

PROCEDURE:

1. Connections are given as per circuit diagram.

2. 3- induction motor is started with DOL starter.

3. If the pointer of one of the wattmeter readings reverses, interchange the current coil terminals and take the reading as negative.

3. The no load readings are taken.

4. The motor is loaded step by step till we get the rated current and the readings of the voltmeter, ammeter, wattmeter, spring balance are

noted.

FORMULAE USED:

1) % slip= (Ns-N/Ns)*100

2) Input Power = (W1+W2)watts

3) Output Power = 2NT/60 watts

4) Torque = 9.81*(S1-S2)*R N-m

5) % efficiency = (o/p power/i/p power)* 100

GRAPHS:


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1) Output Power vs. Efficiency

2) Output Power vs. Torque

3) Output Power vs. Speed

4) Output Power vs. %s

MODEL CALCULATION:


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RESULT:

Thus the performance characteristic of a 3- squirrel cage induction motor by conducting load test has been drawn.


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EX.NO:

DATE: LOAD TEST ON 3-PHASE SLIP RING INDUCTION MOTOR


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O S O 3 S S G UC O O O

AIM:

To conduct a direct load test on a 3-phase slip ring induction motor and to draw its performance characteristics

APPARATUS REQUIRED:

FUSE RATING-

FOR- STATOR- 125% 0f 7.5A = 10A

FOR ROTOR 125% of 11A = 15A

THEORY:

Slip ring induction motor is also called as phase wound motor. The motor is wound for as many poles as the no. of stator poles and always

wound 3- even while the stator is wound two-phase. The other three windings are brought out and connected to three insulated slip-rings

mounted on the shaft with brushes resting on them. These three brushes are further externally connected to a three phase star connected

rheostat. This makes possible the introduction of an additional resistance in the rotor circuit during starting period for increasing starting

torque of the motor.

S.NO NAME OF APPARATUS RANGE TYPE QTY.

1

Ammeter

(0-10)A MI 1


3 Wattmeter (600V,10A) UPF 2

4 Tachometer Digital 1


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PRECAUTIONS:


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1. TPST switch is kept open initially.

2. The external resistance in the rotor circuit should be kept at max. value.

PROCEDURE:

1. Connections are given as per circuit diagram.

2. After observing precautions motor is started on no load.

3. As speed increases, the external resistance is gradually cut out.

4. The no-load readings are taken.

5. If the pointer in one of the wattmeter reverses, interchange the current coil terminals and take the reading as negative.

6. The meter readings are then noted for various load conditions.

FORMULAE USED:

1. Torque= (S1-S2)*9.81*100 N-m

2. O/P Power= 2NT/60 watts

3. I /P Power = (W1+W2) watts

4. % = (o/p power/ i/p power)*1005. %s = (Ns-N)/Ns*100

GRAPHS:

1. O/P power vs Speed


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2. O/P power vs Torque

3. O/P Power vs

4. O/P Power vs slip

5. Torque vs Speed

6. Torque vs Slip

RESULT:

The load test on 3- slip ring induction motor was conducted and the performance characteristics curves were plotted.


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EX.NO.

DATE: NO LOAD AND BLOCKED ROTOR TEST ON 3- PHASE INDUCTION MOTOR


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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.

APPARATUS REQUIRED:-

S.NONAME OF

APPARATUSRANGE TYPE QTY

1. Voltmeter(0-600)V

(0-150)V

MI

MI

01

01

2. Ammeter (0-10)A MI 01

3. Wattmeter(600V,5A)

(150V,10A)

UPF

LPF

01

01

4. Connecting wire As required

FUSE RATING :-

125/100 * 7.5 A 10A

THEORY :-


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A 3-phase induction motor consists of stator, rotor & other associated parts. In the stator

,a 3- phase winding (provided) are displaced in space by 120. A3- 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.

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.

BLOCKED ROTOR 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.

PROCEDURE :-

NO LOAD TEST -

(1). Connections are given as per the circuit diagram.

(2). Precautions are observed and motor is started on the no load.

(3) Autotransformer is varied to have rated voltage applied


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(3). Autotransformer is varied to have rated voltage applied.

(4). The meter readings are then tabulated.

BLOCKED ROTOR 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

FORMULA USED-

FOR NO LOAD TEST-

Wsc = 3 Vo IoCOS watts

Iw = Io cos amps

Ro= V0/ Iw

Xo= Vo/Iu

FOR BLOCKED ROTOR TEST-

Wsc =3I2*Ro watts

Ro1 = Wsc/3(Isc)2

Zo1 = Vsc/Isc Xo1 = Zo1^2-Ro1^2


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TABULAR COLUMNS

NO LOAD TEST:

S.No Voltage Current Wattmeter readings (W1) W1 x mf1 Wattmeter readings (W2) W2 x mf2


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S.No VoltageVoc Volts

CurrentIoc Amps

Wattmeter readings (W1) W1 x mf1 Wattmeter readings (W2) W2 x mf2Observed Reading Actual Reading Observed Reading Actual Reading

1

Voc= open circuit voltage

Ioc = open circuit current

BLOCKED ROTOR TEST:

S.No VoltageVoc Volts

CurrentIoc Amps

Wattmeter readings (W1) W1 x mf1 Wattmeter readings (W2) W2 x mf2Observed Reading Actual Reading Observed Reading Actual Reading

1

Vsc = short circuit voltage

Isc = short circuit current

RESULT:

Thus we determine the equivalent circuit of IM by using no load and blocked rotor test.


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EXP.NO: SPEED CONTROL OF THREE PHASE SLIP RING INDUCTION MOTOR

AIM:

To conduct the speed control test on three phase slip ring induction motor.

APPARATUS REQUIRED:


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S.No Name of the Equipment Range Type Quantity


2 Ammeter (0-1)A MI 1

3 Connecting wires Required

THEORYThese motors are practically started with full line voltage applied across the stator terminals, the value of starting current is adjusted by introducing the

variable resistance in the rotor circuit. The controlling resistance is in the resistance being gradually cut out of the rotor circuit, as the motor attains rated

speed. It has been already shown that by decreasing rotor resistance, the motor attains rated speed and at the same time the starting torque is also

increased due to improvement in power factor.

PROCEDURE


2. Note down the resistance in each phase using Multimeter.

3. Switch ON the A.C power supply.4. Then the speed of the motor is taken for cach resistance per phase.

5. The graph was drawn between resistance and speed.

TABULAR COLUMN:


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speed

Resistance Vs Speed

Resistance


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RESULT

Thus the speed control of three phase slip ring induction motor was performed and the characteristics curves were drawn.

Circuit Diagram


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NAME PLATE DETAILS

EXP.NO: Load test on single phase induction motor

AIM: To determine the efficiency of single phase capacitor start-capacitor run induction motor & to draw its performancecharacteristics.

APPARATUS REQUIRED:


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APPARATUS REQUIRED:

S.No Name Type Range Quantity

Precautions:

1. Check for correct fuse ratings.2. Loose connections should be avoided.3. There should not be any load on the brake drum initially.

Theory:

Refer book : A text book of Electrical Technology (Volume II) B L Theraja & A K Theraja

Procedure:

Connections are made as per the circuit diagram. Supply is given to the motor by closing the DPST switch and motor is startedusing auto transformer. The no load readings of ammeter, voltmeter, wattmeter and tachometer are noted. The motor is loaded graduallyand the readings of ammeter, voltmeter, wattmeter, and spring balance, tachometer are noted and tabulated till the load current is 90% ofits rated value. Then load on the motor is released and motor is switched off.

Formulae used:

1. R = r + (t/2) (m)2. Torque (T) = 9.81 * (S1~S2) * R (Nm)

Tabulation:

1. Circumference of the brake drum = m2. Radius of the brake drum (r) = m

3. Thickness of the belt (t) = m


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S.No

LineVoltage (V)volt

LineCurrent

(I) inampere

Inputpower

inwatt

SpringBalance

Readings inkg

Torque

(T) inNm

Speed rpm

%Slip

Outputpowerin watt

%Efficien

cy

S1 S2 S1~S2

3 . Input Power = W1 watt (wattmeter reading)4. Output power = 2NT / 60 (watt)5. %Slip = (Ns N) / Ns * 100

6. %Efficiency = (output power / Input power) * 100


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Model Graph:


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Result:Thus the load test on single phase induction motor is conducted and its performance characteristics were drawn.


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STUDY OF THREE PHASE INDUCTION MOTOR STARTERS(B) AIM:To study about the AC motor starter.

THREE PHASE INDUCTION MOTOR STARTERS:1. AUTO TRANSFORMERS:It is also known as autotransformers or compensator It consists of an autotransformers with necessary switches or three phase


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It is also known as autotransformers or compensator. It consists of an autotransformers with necessary switches or three phasetransformers reduced voltage is applied to the motor when the motor pick up 80%. So, that the transformer is out-out and full voltage isgiven to the motor most of the autotransformer are provided with 3 sets of tops so as to reduce the voltage to 85, 60 up to 50% of the linevoltage. Again the autotransformer starter may also be provided with stop overload protection and interlocks. The completer scheme of thestarter also included.(a) Interlocks to ensure reduced voltage starting.

(b) Protection against over load etc..,2. STAR DELTA STARTER:The three phase induction motor to be started with the help of the star delta starter must hae its six terminals of the stator winding available.(A1 A2), (B1 B2), (C1 C2). Thus for a 415v across each phase of the stator winding during running.The stator winding is connected instar during starting. Thus for a 415v each winding phase gets 415/_3 = 230V. The starting current is thus reduced in the same proportion (1: _3) and the starting torque isreduce to 1 : 1/_3 compared with the values with full starting. Thus a reduced voltage is applied to the motor during starting.After the motorstarts and attains speed. The connections are changed to delta with the help of the stator and the motor operations at full voltage andhence runs under normal conditions. The star delta starters has the reconnecting arrangement and in addition it has the following features.1. An interlock to prevent direct switching to delta position.2. A push button (or) knob to stop from running condition. After operating this, the switch isbrought to the OFF position.3. An over load protection


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.

This method is used in the case of the motor which one built t run normally with a delta connected starter winding. It consists of two wayswitch connect the motor in star for starting and then delta for normal running. The star connected applied voltage by a factor of 1/_3 andhence the torque developedbecause 1/_3 of that of which would have been developed if the motor war directly connected in the delta. The three types of star delta

starters are:1. Hand Operated2. Semi Automatic


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3. Fully Automatic3. DIRECT ON LINE STARTER (or) D.O.L. STARTER:When fully voltage is supplied across the starters of indction motor, lot of current in drawn by the winding. This is because at the time ofstarting the induction motor are started using direct on line starter on heavy starting curent will flow through the winding such as heavystarting current of short duration may not cause to the motor. Since the construction of induction motor are rugged. More over it takes time

for temperature rise to endanger the utilization of motor windings. But this heavy impression current will cause large voltage drop with thelinear during the period of motor A direct alternate method at starting of induction motor is application up to starting of induction motor. TheON push button is pressed coil A becomes energized and if open contacts are closed when OFF button push button is pressed in a will getenergized and main contacts of the conductor open when themotor starts, in case of overload on the motor the contact of over load may be opened and sub sequently the motor will stop. In case ofover load the overload relay also opens the circuit of the coil and the contactor opens. In case of a supply failure while the motor is running,the coil is deenergized and the motor is isolated from the supply lines. After the supply is resumed the operator has to operate the startpush button for running the motor


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RESULT:Thus the DC and AC Motor starters were studied.

electrical engg cse

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