EM Lab Manual - Cycle - I2

8/3/2019 EM Lab Manual - Cycle - I2

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Ex. No:1 OPEN CIRCUIT AND LOAD CHARACTERISTICS OF

Date : SEPARATELY EXCITIED DC GENERATOR

Aim:

1. To draw open circuit characteristics of the given separately excited DC

generator at rated speed and determine the critical resistance.

2. To determine load characteristics (Internal & External) of the given DC

separately excited generator.

Apparatus required:

Sl.No. Name Range Type Quantity

1 Voltmeter (0-300V) MC 1

2 Ammeter (0-10A)

(0-2A)

MC

MC

1

1

3 Rheostat 300/1.4 A Wire wound 2

4 Tachometer (0-1500) rpm Analog/Digital 1

5 Connecting wires Required

Formula:

Where, Rc Critical resistance

Eg Incremental generated EMF (measured from the linear portion

on the OCC)

If Incremental field current (measured from the linear portion on

the OCC).

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Circuit Diagram:

+

-

DPSTSwitch

Fuse

220VoltsD.C

Supply

+

-

220

VoltsD.CSupply

LF

A

DPSTSwitch

Fuse

F1

F2

A1

A2

3-Point Starter

Motor Name Plate Details

KW________

RPM________

Volts________

Amps________

Fuse

Fuse

VariableResistive

Load

(0-10 A) MC

(0-300 V)

MCDPST

Switch

10 A

10 A

A

A

V

(0-2 A)

MC

F1

F2

Fuse

Fuse

300 /

1.4 A

15 A

15 A

M G

15 A

15 A

300 /

1.4 A

Fuse Rating Calculation

125% of Rated Current

Motor =

Generator =O.C & Load Characteristics of DC Separately Excited Generator

Generator Name Plate Details

KVA________

RPM________

Volts________

Amps________

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Precaution:

1. The field rheostat on the motor side must be kept at minimum resistance position at the

time of starting.

2. The field potentiometer on the generator side must be kept at minimum potential

position at the time of starting.

3. DPST switches must be kept open at the time of power on.

Procedure:

1. Connections are given as per the circuit diagram.

2. Observing the precautions the motor side DPST switch is closed.

3. The motor is started with the help of three- point DC starter slowly.

4. The speed is measured with the help of a hand tachometer.

5. If the speed is below the rated value, then it is brought to the rated value by adjustingthe field rheostat.

6. With DPST switch on the generator field side open, the voltmeter reading is noted

down. (This is the residual voltage at the rated speed at which the motor-generator set is

running now.)

7. The DPST switch on the generator field side is closed.

8. By adjusting the potentiometer on the generator field side suitably for various

increasing field currents, note down the terminal voltages till around 125% of the rated

voltage. The speed is maintained constant throughout this process.

9. The generator terminal voltage is minimized to zero.

10.The speed is brought down to minimum value and the motor is switched off with the

help of DPST switch. (Note the starter holding coil releasing the handle else bring it

back to start position)

Tabulation:

Speed = _________rpm

Residual voltage = ________ Volts

S. No. If(amps) Eg (volts)

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Model graph:

Load Characteristics:

Precaution:

1. The field rheostat on the motor side must be kept at minimum resistance position at the

time of starting.2. The field potentiometer on the generator side must be kept at minimum potential

position at the time of starting.

3. DPST switches must be kept open at the time of power on.

4. There should be no load at the time of starting.

Procedure:

1. Connections are given as per the circuit diagram.

2. Observing the precautions the motor side DPST switch is closed.

3. The motor is started with the help of three- point DC starter slowly.

4. The speed is measured with the help of a hand tachometer.

5. If the speed is below the rated value, then it is brought to the rated value by adjusting

the field rheostat.

6. By adjusting the potentiometer on the generator side the generator terminal voltage is

brought to the rated value.

Eg E

g

If

If

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7. Load side DPST switch is closed.

8. The load is applied gradually. For various load currents voltmeter and ammeter

readings are noted down till full current of the generator. (Avoid sustained overload.)

9. The load is brought back to initial no load position.

10.DPST switch on the load side is opened.

11.Generator field circuit potentiometer is brought to minimum potential position.

12. DPST switch on the generator field side is opened.

13. The speed is brought down to minimum value and the motor is switched off with the

help of DPST switch. (Note the starter holding coil releasing the handle else bring it

back to start position)

14. Disconnect and return the apparatus.

Tabular column:

Ra = _________ Ohms

Load

current

IL(amps)

Shunt

Field

current

I sh(amps)

Load

voltage

VL(volts)

Armature current

Ia = IL

Generated voltage

Eg = V + Ia Ra

Model graph:

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Ia = IL + I sh Amps

Eg = V + Ia Ra Volts

Ra Armaure resistance ohms

Eg generated voltage volts

V Terminal voltage volts

I sh Shunt field current Amps

Result:

1. The Open Circuit Characteristics of the given separately excited DC generator was

obtained and the Critical resistance at rated speed is found to be ______ohms.

2. The Load Characteristics (Internal & External) of the given separately excited DC

generator was obtained.

Ia

& IL

Eg Vs Ia

V Vs IL

V

&Eg

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Ex. No: LOAD CHARACTERISTICS OF SELF EXCITIED

Date : DC SHUNTGENERATOR

Aim:

1. To determine load characteristics (Internal & External) of the given DC self excited

generator.

Apparatus required:

Sl. No Name Range Type Quantity

1 Voltmeter (0-300) V MC 1

2 Ammeter (0-10) A MC 1

3 Ammeter (0-2) A MC 1

4 Rheostat300 / 1.4 A

100 / 4 AWire wound Each 1

5 Tachometer Analog / Digital


Formulae:

Eg = V + Ia Ra

Ia = IL + I sh

Where,

Ra Armature resistance

Eg Generated voltage

V Terminal Voltage

I sh Shunt field current

IL Load Current

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Circuit Diagram:

+

-220 Volts

D.C

Supply

LF

A

DPSTSwitch

F1

F2

A1

A2

3-Point Starter

M

FuseFuse

A

v

Fuse

VariableResistive

Load

(0-10 A)

MC

(0-300 V)MC

(0-2 A)

MC

f1

f2

100 /4A

DPST

SwitchFuse

300 /

1.4 A

15 A

15 A 10 A

10 A

G

A1

A2


KW________

RPM________

Volts________

Amps________

Generator Name Plate Details

KVA________

RPM________

Volts________

Amps________



Motor =

Generator =

O.C & Load Characteristics of DC Shunt Generator

A

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Precaution:

The field rheostat on the motor side must be kept at minimum resistance position at

the time of starting.

The field rheostat on the generator side must be kept at maximum resistanceposition at the time of starting.

DPST switches must be kept open at the time of power on.

There should be no load at the time of starting.

Procedure:

Connections are given as per the circuit diagram.

Observing the precautions the motor side DPST switch is closed. The motor is started with the help of three- point DC starter slowly.

The speed is measured with the help of a hand tachometer.

If the speed is below the rated value, then it is brought to the rated value by

adjusting the motor field rheostat.

By adjusting the field rheostat on the generator side the generator terminal voltage is

brought to the rated value.

Load side DPST switch is closed.

The load is applied gradually. For various load currents voltmeter and ammeter

readings are noted down till full current of the generator. (Avoid sustainedoverload.)

The load is brought back to initial no load position.

DPST switch on the load side is opened.

Generator field circuit rheostat is brought to maximum resistance position.

DPST switch on the generator field side is opened.

The speed is brought down to minimum value and the motor is switched off (Note

the starter holding coil releasing the handle else bring it back to start position)

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Tabular column:

Ra = ________ Ohms

S.

No.IL(amps)

I sh(amps)

V(volts)Ia = IL + I sh

(amps) Eg = V + Ia Ra

Model graph:

Result:

Ia

& IL

Eg

Vs Ia

VL

Vs IL

VL&

Eg

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Thus the Load Characteristics (Internal & External) of the given self-excited DC

shunt generator was obtained.

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12/43

Ex. No: LOAD TEST ON DC SHUNT MOTOR

Date :

Aim:

To perform load test on the given D.C shunt motor and to obtain the performance

characteristics.

Apparatus Required:

Sl.No Name of the apparatus Range Type Quantity

1. Ammeter (0-2) A

(0-20) A

MC Each 1

2. Voltmeter (0-300) V MC 1

3. Tachometer (0-1500) rpmAnalog/Digita

l1

4. Rheostat 300/1.4 A Wire wound 1

5. Connecting wires Required

Formulae:

IL = Ia + I sh

Input power = V x IL (Watts)

Torque (T) = (S 1 ~ S 2) x 9.81 x R (Nm) S 1, S 2 spring balance readings (Kg)

Output power = 2 N T (Watts) N speed of the motor in rpm

60

Efficiency = Output power x 100

Input power Ia - Armature current (Amps) I sh Shunt field current (Amps)

IL - Load Current (Amps) V Supply voltage (Volts)

R Radius of the brake drum = Circumference / 2 (m).

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Circuit Diagram:

+-

220 VoltsD.C

Supply

DPSTSwitch

A1

A2

Fuse

Fuse

15 A

15 A

M

LF

A

F1

F2

3-Point Starter

300 /

1.4 A

A

A

V

(0-20 A) MC

(0-300 V)

MC

(0-2 A)MC

SpringBalance

BrakeDrum

S1 S2


KW________

RPM________

Volts________

Amps________



Motor =

Load Test on DC Shunt Motor

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Tabular column:

Sl.No

Input

voltage(Volts)

(V)

Load

Current(Amps)

(IL)

Field

Current(Amps)

(Ish)

Armature

Current(Amps)

(Ia = IL - Ish )

Speed(N)

(rpm)

Spring Balance

Readings Torque(T)

(Nm)

InputPower

(Watts)

OutputPower

(Watts)

Efficienc(%)S1

kg

S2kg

(S1~ S2)

kg

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Model Graph:

ELECTRICAL CHARACTERISTICS MECHANICAL CHARACTERISTICS PERFORMANCE CHARS

Torque (T)(Nm)

23

4

1 Output Vs Speed

2 Output Vs % Efficiency

3 - Output Vs Torque

4 Output Vs Armature Current

Speed (N)

% Efficiency ()

Torque (T)Arm. Current (Ia)

Output power in wattsTorque (Nm)Arm. Current (Ia) in Amps

Speed (N)(rpm)

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Precautions:

1. The motor field rheostat must be kept at minimum resistance position at

the time of starting.

2. There should be no load at the time of starting.

Procedure:

Make the connections as per the circuit diagram

Switch on the supply and move the starter handle slowly and gradually to start the motor

Now observe the speed. If the speed is less than the rated speed adjust the field

rheostat and bring the speed to rated value. Readings are taken for no load.

Load on the motor is varied with the help of pony brake arrangement.

Spring balance, ammeter, voltmeter and speed-readings are noted down for various

line currents as the load is increased (till the rated current is reached).

Pour water in the brake drum to avoid over heating.

Unload the machine and bring back the rheostat to minimum position.

Switch off the supply

Result:

Thus the load test on the given DC Shunt motor was conducted and its performance

characteristics were drawn.

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Ex. No: LOAD TEST ON DC SERIES MOTOR

Date :

Aim:

To perform load test on the given D.C shunt motor and to obtain the performance

characteristics.

Apparatus Required:


1. Ammeter (0-20) A MC 12. Volt meter (0-300) V MC 1

3. Tachometer (0-1500) rpmAnalog/Digita

l1


Formulae:

IL = Ia = ISe

Input power = V x IL (Watts)

Torque (T) = ( S 1 ~ S 2 ) x 9.81 x R (Nm) S 1 , S 2 spring balance readings(Kg)

Output power = 2 N T (Watts) N speed of the motor in rpm

60

Efficiency = Output power x 100

Input power

Ia - Armature current (Amps) I se Series field current (Amps)

IL - Load Current (Amps) V Supply voltage (Volts)

R Radius of the brake drum = Circumference / 2 (m)

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Circuit Diagram:

+

-220 Volts

D.CSupply

DPSTSwitch

A1

A2

Fuse

Fuse

15 A

15 A

M

2-Point Starter

A

V

(0-20 A) MC

(0-300 V)

MC

SpringBalance

Brake

Drum

S1 S2


KW________

RPM________

Volts________

Amps________



Motor =

L A

S1 S2

Load Test On DC Series Motor

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Tabular column:

Sl.

No

Inputvoltage

(Volts)

(V)

Load

Current

(Amps)

(IL = Ia)

speed

(N)

(rpm)

Spring Balance

Readings Torque

(T)

(Nm)

Input

Power

(Watts)

Output

Power

(Watts)

Efficiency

(%)S1kg

S2kg

(S1~ S2)kg

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Model Graph:

ELECTRICAL CHARACTERISTICS MECHANICAL CHARACTERISTICS PERFORMANCE CHARS

% EfficiencySpeed Speed

(N) Torque

Torque (T) rpm Arm. Current(Nm)

Arm. Current (Ia) in Amps Torque (Nm)

Output power in watts

4

1 Output Vs Armature Current

2 Output Vs Torque

3 Output Vs % Efficiency

4 Output Vs Speed

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Precautions:

1. The motor should be started with some load.

2. Brake drum should be cooled throughout the experiment.

Procedure:

1. Connections are given as per the circuit diagram

2. Observing the precautions the DPST switch is closed.

3. The motor is started with the help of two-point dc starter slowly.

4. Load on the motor is varied with the help of pony brake arrangement.

5. Spring balance, ammeter, voltmeter and speed readings are noted down for

various line currents as the load is applied. Care must be taken to avoid the speed

reaching dangerously high values while reducing the load.

6. Pour water in the brake drum to avoid overheating.

7. At a minimum safe load the DPST switch is opened.

8. Disconnect and return the apparatus.

Result:

Thus the load test on the given DC Series motor was conducted and its performance

characteristics were drawn.

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Ex. No: SPEED CONTROL OF DC SHUNT MOTOR

Date :

Aim:

To vary the speed of the given dc shunt motor by the following methods.

(i). Armature control method (below rated speed)

(ii). Field control method (above rated speed)

Apparatus Required:

Sl. No Name of the apparatus Range Type Quantity

1. Ammeter (0-2) A M.C 1

2. Volt meter (0-300) V M.C 1

3. Tachometer (0-1500) rpm Analog/Digital 1

4. Rheostat300 / 1.4 A

100 / 4 AWire wound Each 1


Precautions:

1. The field rheostat must be kept at minimum resistance position at the time of starting.

2. The armature rheostat must be kept at maximum resistance position at the time of

starting.

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Circuit Diagram:


KW________

RPM________

Volts________

Amps________

+

-220

Volts

D.C

Supply

DPST

Switch

A1

A2

Fuse

Fuse

2 A

2 A

V

(0-300 V)

MC



Motor =

F1

F2

300 /

1.4 A

(0-2.5 A)

MC

M V

100 / 4 A

Speed Control of DC

Shunt Motor

A

Model Graph:

(i) Armature Control method (ii) Field control method

Speed

(Rpm) Speed

(Rpm)

Armature voltage (volts) Field current (amps)

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Tabulations:

(i). Armature control method:

Field current (If) = ______ Amps kept constant

SL.

No

Armature voltage

(Volts)

Speed

(rpm)

(ii) Field control method

Armature voltage (Va) = ______ Volts kept constant

SL.

No

Field current

(Amps)

Speed

(rpm)

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Procedure:

(i). Armature control method:


Switch on the supply

Keep the field current constant and for different armature voltage (by varying

armature rheostat) note down the corresponding speed.

Bring back the rheostat to initial position and switch off the supply

(ii). Field control method

Switch on the supply

Start the motor by closing the DPST switch

Keep the armature voltage constant and for various field current (by varying field

rheostat) note down the corresponding speed.

Bring back the rheostat to initial position and switch off the supply

Result:

Thus the speed of the given DC shunt motor is varied by both armature control

and field control method and the graphs are plotted. The speed is directly proportional to

the armature voltage by graph (i) and inversely proportional to the field current by graph

(ii).

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Ex. No: OC AND SC TEST OF SINGLE PHASE TRANSFORMER

Date :

Aim:

To perform open circuit and short circuit test on a single phase transformer and

predetermine the efficiency at various loads and also draw the equivalent circuit.

Apparatus Required:


1. Ammeter (0-2) A

(0-5) AMI Each 1

2. Volt meter (0-150) V

(0-30) VMI Each 1

3. Watt meter 150V, 2A, LPF

30V, 5A, UPFDynamo meter Each 1

4. 1- Autotransformer (0-270) V 1


Formulae:

Transformer Ratings: 1 KVA, 220 V/ 110V, 50HZ

V1 = 220 V & V2 = 110 V

I 1 = 1000/220 = 4.55 A & I2 = 1000/110 = 9.09 A

K = V2 / V1 = 110/220 = 0.5

From open circuit test:

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In the open circuit test the primary is open circuited and the meters are connected on

L.V side, which is secondary of the transformer. Thus O.C test will give us no load

current, I01. (i.e referred to secondary)

Since K = V2/V1, the corresponding no load primary current, I0 = I01 * K

W0 = V1 I0 Cos 0 ( watts)

Where,

W0 = No load input power = core (or Iron) loss = Wi

I0 - No load input current

V1 - No load rated input voltageCos - Power factor

Cos 0 = W0 / V1 I0I w = I0 Cos 0 A ( Iron loss component)

I = I0 Sin 0 A ( Magnetizing component)

R0 = V1 / I w (Resistance to represent core loss)

X0 = V1 / I (Reactance to represent magnetizing component)

From short circuit test:

In the Short circuit test the secondary is short circuited and the meters are on H.V

side, which is primary of the transformer. Hence it gives parameters referred to primary.

R01 = Wsc / Isc2

Z01 = Vsc / Isc

X01 = Z012 - R012

I21 = I2 * K & I1 = I0 + I2

1

Where,

R01 - Equivalent resistance of transformer referred to primary side

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X01 - Equivalent reactance of transformer referred to primary side

Z01 - Equivalent impedance of transformer referred to primary side

Wsc Full load copper loss

Isc Short Circuit Current

Vsc Short circuit voltage corresponding to Isc

Equivalent Circuit Parameters referred to secondary side:

R01 = R0 * K

2 I01 = No load current from O.C Test

X01

= X0 * K2

I w1

= V11

/ R01

R02 = R01 x K2 I

1 = V11 / X0

1

X02 = X01 x K2 Where, V1

1 = V1 * K

Z02 = Z01 x K2 I1

1 = I01 + I2

Regulation = [ I2 R02 Cos + I2 X02 Sin / V2 ] X 100

+ Ve for lagging Power factor

- Ve for leading power factor

(X * KVA * P.f)

% Efficiency at various loads = x 100

[(X * KVA * P.f ) + (Wi + X 2 Wsc)]

X Load ratio

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Circuit Diagram:

DPSTSwitch

Fuse

230 V

1- 50 HZ

AC Supply V

A

C

M L

V

Fuse

5 A

5 A

(0-270 V) 1

AutoTrnsformer (0-150 V)MI

(0-2 A) MI

150 V, 2A, LPF

Wattmeter

110 V 220 V

Open Circuit

Name Plate Details

Single Phase Transformer

Auto TransformerFuse Rating Calculation

KVA________

Voltage Ratio________

20 % of Rated Current(Max. Load of A.T )

Maximum Load =

Maximum KVA =

Input =

0 V 0 V

Open Circuit Test on Single Phase Transformer

P

N

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Circuit Diagram:

DPST

Switch

Fuse

230 V1- 50 HZ

AC Supply V

A

C

M L

V

Fuse

5 A

5 A

(0-270 V) 1

Auto

Trnsformer

(0-30 V)

MI

(0-5 A) MI

30 V, 5A, UPF

Wattmeter

220 V 110 V


Short Circuit

0 V 0 V

Isc = KVA / V

= Short Circuit Test on Single Phase Tranformer

P

N

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Equivalent circuit referred to primary side:

V1

I21

I0

I1

IW I

X0R0

R01 X01

ZL1

V21

Equivalent circuit referred to secondary side:

V11

I11

I01

I2

IW1 I

1

X01R0

1

R02 X02

ZL

V2

Model Graph:

UPF

%Reg.

% 0.8

Leading P.F Lagging P.F

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O/P Power (Watts) %Reg.

Tabulations:

Open circuit test:

Short circuit test:

Sl.

No

Vo

(Volts)

Io

(Amps)

Wo

(Div)

Wo x M.F

(Watts)

Sl.

No

Vsc(Volts)

Isc(Amps)

Wsc(Div)

Wsc x M.F

(Watts)

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Tabulation for determine the Efficiency:

Sl.

No

Load

ratio

(X)

Output power

(Watts)

Wi(Watts)

Wcu(Watts)

Input Power

(Watts)

%

Efficiency

UPF 0.8 UPF 0.8 UPF 0.8

1

2

3

41

Tabulation for determine the Regulation:

Sl.No Power Factor (Cos )

% Regulation

Leading Lagging

1 0

2 0.2

3 0.4

4 0.6

5 0.8

6 1.0

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Precautions:

Autotransformer must be kept at minimum potential point during starting condition.

Procedure:

Open circuit test:


Switch on the supply and vary the autotransformer to get rated voltage

Note down ammeter, voltmeter and wattmeter readings.

Bring back the autotransformer to original position.


Short circuit test:


Switch on the supply and vary the autotransformer to get rated short circuit current.

Note down ammeter, voltmeter and wattmeter readings.

Bring back the autotransformer to original position.


Result:

Thus the open circuit and short circuit tests were performed on a single-phase

transformer and the efficiency was predetermined at various loads.

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Ex. No: LOAD TEST ON SINGLE PHASE TRANSFORMER

Date :

Aim:

To perform load test on a single phase transformer and determine its performance

characteristics

Apparatus Required:

Sl.no Name of the apparatus Range Type Quantity

1. Ammeter (0-5) A

(0-10) AMI Each 1

2. Volt meter (0-150) V

(0-300) VMI Each 1

3. Watt meter 150V, 5A, UPF

300V, 10 A, UPFDynamo meter Each 1

4. 1- Autotransformer (0-270) V 1


Formulae:

Input power = W1 x M.F1 watts

Output power = W2 x M.F2 watts

% Efficiency = Output power / Input power X100

% Regulation = (E02 V2) / E02 x 100

E 02 - No load secondary voltage

V 2 - Secondary voltage at various loads

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M.F Multiplication factor

W1, W2 - Wattmeter readings

V I cos Multiplication factor (M.F) =

No of divisions in the watt meter

Precautions:

Autotransformer must be kept at minimum potential point during starting condition.

There should be no load at the time of starting the experiment

Procedure:

Make the connections as per the circuit diagram.

Switch on the supply and vary the autotransformer to get rated primary voltage.

Note down the no load readings.

Add the load in steps and note down all the meter readings till the rated secondarycurrent is reached.

Remove the load and bring back the autotransformer to original position.

Switch off the supply.

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Circuit Diagram:

DPST

Switch

Fuse

230 V1- 50

HZ AC

Supply

A

C

M L

V

Fuse

15 A

15 A

(0-270 V)

1 Auto

Trnsform

er

(0-150 V)

MI

(0-5 A) MI

150 V, 5A, UPF

Wattmeter

110 V 220 V


0 V 0 V

Load Test on Single Phase Tranformer

C

M L

V

A

DPST

Switch

Fuse

Fuse

10 A

10 A

(0-10 A) MI

300 V, 10A, UPF

V V(0-300 V)

MI

Wattmeter

Load

Name Plate Details

Primary Side Secondary Side

Power =

Voltage =

Current =

Power =

Voltage =

Current =

Primary Side: 125 % of Rated Current

=

Secondary Side: 125 % of Rated Current

=

P

N

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Tabulation:

Sl. Primary

Voltage

Primary Input Power Secondary

Voltage

Secondar Output PowerEfficiency Reg

W1 W1 X M.F W2 W2 X M.F

(Volts) (Amps) (Div) (Watts) (Volts) (Amps)(Div

(Watts) %

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40/43

Ex. No: SWINBURNES TEST(No load Test)

Date :

Aim:

To predetermine the efficiency of DC shunt machine at various load current while

operating as a motor and generator and plot a graph output Vs % efficiency.

Apparatus required:

Sl. No. Name Range Type Quantity

1 Voltmeter (0-300) V MC 1

2 Ammeter (0-2.5) A MC 2

3 Rheostat 300 / 1.4 A Wire wound 1

4 Tachometer Analog / Digital 15 Connecting wires Required

Formula:

Constant Losses WC = Input Power - No load Armature copper loss

= VIo Iao2X Ra

Where, Iao= Io - IfRa = Armature resistance

For motor:1. Ia = IL If Amps

2. Armature copper loss = Ia2 Ra watts

3. Total loss WT = WC +Ia2 Ra watts

4. Input power = V IL watts

5. Output Power = Input Power Total Loss watts

6. Efficiency % m = [Output Power / Input Power ] X 100 No unit

For Generator:

1. Ia = IL +If Amps

2. Armature copper loss = Ia2 Ra watts

3. Total loss WT = WC +Ia2 Ra watts

4. Output power = V IL watts

5. Input Power = Output Power + Total Loss watts

6. Efficiency % G = [Output Power / Input Power ] X 100 No unit

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Circuit Diagram:


KW________

RPM________

Volts________

Amps________

+

-220

VoltsD.C

Supply

DPST

Switch

A1

A2

Fuse

Fuse

2 A

2 A

M

LF

A

F1

F2

3-Point Starter

300 /

1.4 A

A

A

V(0-300 V)

MC

(0-2.5 A)

MC

(0-2.5 A)MC



Motor =

Swinburnes Test

Model graph:

%

Output (watts)Tabulation:

Sl. No V (volts) I0 (amp) If(amp)

Generator

Motor

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Motor:

Ra = _______ Ohms

Sl.

No

V

(volts)

IL(amp)

Ia=IL-If(amp)

Ia2Ra

_(watts)

WC

_(watts)

WT =WC+Ia2Ra

_(watts)

Input

VIL

_(watts)

Output

_(watts)%

Generator:

Ra = _______ Ohms

Sl. NoV

(volts)

IL(amp)

Ia=IL+I

f

(amp)

Ia2Ra

_(watts

)

WC

_(watts)

WT=WC+Ia

2Ra

_(watts)

Outpu

t

VIL

_(watt

s)

Input

_(watts)

%

Precautions:

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

Procedure:

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1. Connections are made as per the circuit diagram.

2. Observing the precaution the DPST switch is closed and the motor is started with

the help of 3-point DC starter slowly.

3. The motor field rheostat is adjusted and the motor is brought to rated speed.

4. The voltmeter and ammeter readings are noted down

5. Field rheostat is brought back to minimum position

6. Disconnect and return the meters.

Result:

The efficiency of the dc shunt machine was determined when it was running as a

generator as well as a motor.

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EM Lab Manual - Cycle - I2

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