EM lab for ECE

7/30/2019 EM lab for ECE

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Ex.No:3

LOAD TEST ON DC SHUNT MOTOR

Date:

AIM

To conduct a load test on DC Shunt motor and to obtain the load characteristics

a) Output power Vs Efficiency

b) Output power Vs Speedc) Output power Vs Torque

d) Speed Vs Torque.

APPARATUS REQUIRED

PRECAUTIONS

1. DPST Switch should be in open position.

2. The field regulating rheostat should be in minimum position.

3. Belt on brake drum in loose position (i.e.) Motor should be at No-load.

PROCEDURE

For Load Test

1. Connections are made as shown in the circuit diagram.2. Switch on the DC power supply.

3. Close the DPST switch and start the motor using 3-Point starter.

4. The field rheostat of the motor was adjusted such that the Motor runs at its rated speed.

5. Note down the No-load reading.6. The load was increased in steps by adjusting the tension in the belt over brake drum and the

corresponding readings of Voltmeter, Ammeter and speed was noted, the loading was done till

the rated current was achieved.

SL.No Apparatus Name Type Range Quantity

1. Ammeter PMMC (0-15A) 12. Voltmeter PMMC (0-300V) 1

3. Rheostat - 250,2A 1

4. Tachometer - - 1


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7. After taking all sets of readings, the load was brought to the No-load condition and the rheostat

was brought to the initial position and then switch off the DC supply.

8. Now calculations were done and the Performance characteristics were drawn.

TABULATION

For Load Test

No InputVoltage

VL (V)

LineCurrent

IL (A)

Load(Kg) S1- S2

(Kg)

SpeedN

(rpm)

TorqueT

(N-m)

OutputPower

PO (w)

InputPower

Pi (W)

Efficiency

(%)

S1 S2

Model Calculation

Circumference of the brake drum (2r) = _______* 10-2 m.

Radius of the brake drum (r) = ________* 10-2 m.

Speed (N) = _________ rpm.

Line Current IL = ______ A.

Input (or) Line Voltage VL = _______ V.

Input Power (Pi) = VL * IL = _______ W.

Load = S1 - S2 = _______ Kg.

Torque (T) = 9.81 * (S1 - S2) * r = _________ N-m.

Output Power (Po) = (2NT)/60 = _________ W.


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% Efficiency () = (Output power / Input power) * 100 = ______ %.

Model Graph

RESULT

Thus the Load test was performed in DC Shunt motor and its performance characteristics like

a) Output power Vs Efficiency

b) Output power Vs Speed

N

T

Output Power Po(W) Torque T (N-m)

SpeedN

(rpm

)

(N Vs T)

SpeedN(rpm)

Efficiency (%)TorqueT

(N-m)


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c) Output power Vs Torque

d) Speed Vs Torque was plotted.

The Maximum efficiency of the DC shunt motor was _____ %.

Ex.No:4

SWINBURNES TEST

Date:

AIM

To perform Swinburnes test on the given D.C shunt machine and to

Predetermine the efficiency of the machine while running as (i) Generator and (ii) Motor.

APPARATUS REQUIRED

PRECAUTIONS


2. Motor side field regulating rheostat should be in minimum position.


PROCEDURE


1. Ammeter PMMC (0-2A)(0-10A)

1 each

2. Voltmeter PMMC (0-300V)(0-30V)

1 each


4. Resistive load 1 230 V,3KW 1

5. Tachometer - - 1


5/24

For No-Load Test

1. Connections are made as shown in the circuit diagram.2. Switch on the DC power supply and Close the DPST switch and start the motor using 3-Point

starter.

3. Adjust the field rheostat of the motor to run at rated speed.4. Note down the No-load reading.

For Measurement of Ra

1) Connections are made as shown in the circuit diagram.

2) Switch on the DC power supply and close the DPST switch.

3) Apply the load in steps and note down the corresponding readings.4) By using the formula, the armature resistance was found.

Ra = Va / Ia

TABULATION

For No-Load Test

SL.No No-Load

Armature Current

Iao (A)

Field Current

If(A)

No-Load

Voltage

Vo (V)

Speed

N

(rpm)


S.No Armature VoltageVa (V)

Armature CurrentIa (A)

ArmatureResistance

Ra = Va / Ia()

Mean Ra = ---------

For PREDETERMINATION OF AS MOTORSL.No Field

Current

No-Load

Armature

Line

Current

Armature

Current

Arm.Cu.loss

Ia2Ra

Output

Power

Input

Power Efficiency


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Ish (A) Current

Iao (A)

IL (A) Ia = IL-Ish(A)

(W) PO(W) Pi (W) (%)

For PREDETERMINATION OF AS GENERATORSL.No Field

CurrentIsh (A)

No-Load

ArmatureCurrent

Iao (A)

Line

CurrentIL (A)

Armature

CurrentIa = IL+Ish

(A)

Arm.Cu.loss

Ia2Ra

(W)

Output

PowerPO(W)

Input

PowerPi (W)

Efficiency (%)

Model Calculation

From No-Load Test

No-Load input power = VO * ILO = Total Losses = __________ W.

Total Loss = Armature Cu. Loss + constant loss = _________ W.

Constant Loss WC = Total loss No load Arm.Cu.loss = _________ W.

PREDETERMINATION OF AS MOTORIL = ___ A; Ish = ____ A.

Armature Current Ia = IL- Ish = ______ A.

Arm.Cu.loss = Ia2Ra = ____ W.

Input Power Pi = VO * ILO = _____ W.

Output Power PO = Input Power Total losses = ______ W.

Total Loss = Arm.Cu loss + Constant loss = ____ W.

% Efficiency = (Output power / Input power) * 100 = _____%.

PREDETERMINATION OF AS GENERATOR


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IL = ___ A; Ish = ____ A.

Armature Current Ia = IL+ Ish = ______ A.

Arm.Cu.loss = Ia2

Ra = ____ W.

Input Power Pi = Motor Input Power + Arm.Cu loss + Constant loss = _____ W.

Output Power PO = VO * ILO = ______ W.

% Efficiency = (Output power / Input power) * 100 = _____%.

Model Graph

For Motor

For Generator

Efficiency

(%)

Output Power Po (W)


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RESULT

Thus the swinburnes test is conducted on a DC Shunt machine and its efficiency waspredetermined while it is operating as i) Motor and ii) Generator and the constant loss of the machine

was found WC = _____ W and the characteristics curve was plotted.

Ex.No:5

SPEED CONTROL OF DC SHUNT MOTOR

Date:

AIM

To obtain the speed control characteristics of DC Shunt motor by i) Field Control method and

ii) Armature Control method.

APPARATUS REQUIRED

Efficiency

(%)

toitsinitialposition

andswitchofftheDcsupply.at'farmatur

evoltagethecorrespondingreadings

ofammetarethod.



1 each

2. Voltmeter PMMC (0-300V)(0-30V)

1each

3. Rheostat - 250,2A150,5A

1each

4. Tachometer - - 1


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PRECAUTIONS

1. DPST Switch should be in open position.2. Motor side field regulating rheostat should be in minimum position.

3. Armature side regulating rheostat should be in maximum position.


PROCEDURE

For Field Control Method

1. Connections are made as per the circuit diagram.

2. Switch on the DC Power supply and close the DPST switch.3. Start the motor using 3-point starter and adjust the field rheostat to run the motor at its rated

speed.

4. Decrease the Armature circuit rheostat gradually and bring the motor armature Voltage (Va) toa Constant Value.

5. Now Note-down the readings, and then increase the field rheostat in steps, for each value of the

field current the corresponding readings of ammeter and speed were noted.

6. After taking different sets of readings, the rheostats were brought to the initial position.7. Switch off the DC power supply.

For Armature Control Method


2. Switch on the DC Power supply and close the DPST switch.

3. Start the motor using 3-point starter.4. Motor field rheostat was adjusted till the motor runs at its rated speed.

5. Note down the field current and keep it as the constant field current.

6. Now note down the corresponding Voltmeter, Ammeter readings and speed also noted.7. The armature rheostat was varied in steps, for each value of armature voltage the

corresponding readings of ammeter, voltmeter and speed were noted.

8. After taking all sets of readings bring back the rheostats to its initial position andswitch off the Dc supply.



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1) Connections are made as shown in the circuit diagram.

2) Switch on the DC power supply and close the DPST switch.

3) Apply the load in steps and note down the corresponding readings.4) By using the formula, the armature resistance was found.

Ra = Va / Ia

TABULATION

For Field Control Method

S.No

Armature Voltage Va = V Armature Voltage Va = V

FieldCurrent

If(A)

ArmatureCurrent

Ia (A)

SpeedN

(rpm)

FieldCurrent

If(A)

ArmatureCurrent

Ia (A)

SpeedN

(rpm)

For Armature Control Method

S.No

Field Current If= A Field Current If= A

Armature

CurrentIa (A)

Armature

VoltageVa (V)

Speed

N(rpm)

Back EMF

Eb = Va-IaRa(V)

Armature

Current

Ia (A)

Armature

Voltage

Va (V)

Speed

N

(rpm)

Back EMF

Eb = Va-IaRa(V)


S.No Armature Voltage

Va (V)

Armature Current

Ia (A)

Armature Resistance

Ra = Va / Ia ()

Mean Ra = --------- .

MODEL GRAPH


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RESULT

Thus the Field Control and Armature Control Methods of Speed Control were practiced on DC

Shunt Motor and Speed control characteristics are plotted.

Ex.No:6

LOAD TEST ON DC SERIES MOTOR

Date:

AIM

To conduct a load test on DC Series motor and to obtain the load characteristics like

a) Output power Vs Efficiency.

b) Output power Vs Speed.c) Output power Vs Torque.

d) Output power Vs Load Current.

If1

If2

Spe

edN(rp

m)

Speed

N(rp

m)

Back EMF Eb

(V)Field Current If(A)

Va2

Va1

For Field Control For Armature Control


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e) Speed Vs Torque.

APPARATUS REQUIRED

PRECAUTIONS

1. Starter should be in OFF position before switching ON the supply.


3. There should be some load applied on the brake drum at the time of starting.

PROCEDURE

1. Connections are made as shown in the circuit diagram.2. Observe the precaution and Switch on the DC power supply.

3. With some load on the brake drum start the motor using Starter.

4. Vary the load for armature current upto rated current and note down the correspondingreadings of the Voltmeter, Ammeter, load and speed.

5. After taking all sets of readings switch off the DC supply.

8. Now calculations were done and the Performance characteristics were drawn.

TABULATION

No Input

VoltageVL (V)

Line

CurrentIL (A)

Load

(Kg) S1- S2(Kg)

Speed

N(rpm)

Torque

T(N-m)

Output

PowerPO (w)

Input

PowerPi (W)

Efficiency (%)


1. Ammeter PMMC (0-15A) 12. Voltmeter PMMC (0-300V) 1

3. Tachometer - - 1


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S1 S2

Model Calculation

Circumference of the brake drum (2r) = _______* 10-2 m.

Radius of the brake drum (r) = ________* 10-2 m.

Speed (N) = _________ rpm.

Line Current IL = ______ A.

Input (or) Line Voltage VL = _______ V.

Input Power (Pi) = VL * IL = _______ W.

Load = S1 - S2 = _______ Kg.

Torque (T) = 9.81 * (S1 - S2) * r = _________ N-m.

Output Power (Po) = (2NT)/60 = _________ W.

% Efficiency () = (Output power / Input power) * 100 = ______ %.

Model Graph


14/24

RESULT

Thus the Load test was performed in DC Series motor and its performance characteristics like

a) Output power Vs Efficiency.

b) Output power Vs Speed.c) Output power Vs Torque.

d) Output power Vs Load current.

e) Speed Vs Torque was plotted.

The Maximum efficiency of the DC series motor was _____ %.

Ex.No:2 OPEN CIRCUIT AND LOAD CHARACTERISTICS OF

Date: SEPARATELY-EXCITED DC GENERATOR

IL

N

T

Output Power Po(W) Torque T (N-m)

SpeedN

(rpm

)

(N Vs T)

SpeedN(rpm)

Efficiency(%)

TorqueT(N-m)Load

currentIL

(A)


15/24

AIM

To obtain the open circuit and Load characteristics of a separately-excited DC Generator.

APPARATUS REQUIRED



1 each

2. Voltmeter PMMC (0-300V)

(0-30V)

1 each


4. Tachometer - - 1

5. Resistive load 1 230 V,3KW 1

PREACAUTIONS

1. DPST switch should be in open position.

2. Motor side regulating rheostat should be in minimum position.

3. Generator side regulating rheostat should be in maximum position.

PROCEDURE

For OCC test

1. Connections are made as shown in the circuit diagram.2. Switch on the DC power supply.

3. Close the DPST switch (1) and start the motor using 3-Point starter.

4. The field rheostat of the motor was adjusted such that the Motor-Generator set runs at its rated

speed.5. Now note down the residual voltage of generator using Voltmeter.

6. Vary the field rheostat of the generator and note down the corresponding readings of Ammeter

and Voltmeter.7. Repeat the step 6 till the built up voltage is 10% greater than the rated voltage.

8. Ensure that speed of the generator is maintained at constant speed for all readings.

For Load Test

1. Connections are made as shown in the circuit diagram.


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2. Switch on the DC power supply.

3. Close the DPST switch (1) and start the motor using 3-Point starter.

4. The field rheostat of the motor was adjusted such that the Motor-Generator set runs at itsrated speed.

5. Note down the No-Load reading from ammeter and voltmeter.

6. Now Close the DPST switch (2) and increase the load in steps while the speed wasmaintained constant and the corresponding ammeter, voltmeter readings were noted.

7. The generator was loaded upto the rated load current and then the Load and rheostats were

brought to the initial position and the supply was switched off.8. Now from the readings the load characteristics were plotted.


1. Connections are made as shown in the circuit diagram.

2. Switch on the DC power supply and close the DPST switch.

3. Apply the load in steps and note down the corresponding readings.

4. By using the formula, the armature resistance was found.Ra = Va / Ia

TABULATION

For OCC test

S.No Field Current

If(A)

Generated Voltage

Eg (V)

Speed

N (rpm)

For Load Test

S.No Load

Current

IL (A)

Terminal

Voltage

VL (V)

Field

Current

If(A)

Armature

Current

Ia = IL (A)

Speed

N

(rpm)

Generated

Voltage

Eg = V+IaRa (V)



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S.No Armature Voltage

Va (V)

Armature Current

Ia (A)

Armature Resistance

Ra = Va / Ia ()

Mean Ra = ---------

Model Calculation

For OCC test

Residual Voltage = ----------- V

Critical Resistances Rc = V / I (From the Graph)

For Load Test

Load Current (IL) = ---------- A.

Terminal Voltage VL (V) = ---------- V.

Field Current (IF) = ---------- A.

Armature Current (Ia) = Ia = IL = ---------- A.

Generated Voltage (Eg) = V+IaRa = ---------- V.

Model Graph


18/24

OCC Load Characteristics

RESULT

Thus the No-Load/Open circuit and Load characteristics of separately excited DC Generator

was performed and the following results were obtained

i) The value of Residual voltage = ------------------ V at rated speed.

ii) The critical resistance value Rc = ---------------- .

And the OCC and Load characteristics are obtained and plotted.

Load Test on Single - Phase Squirrel Cage Induction Motor

I

V

Field Current IF(A)

Load Current IL (A)&

Armature Current Ia (A)

Generated

VoltageEg&

TerminalVoltage

VL

(V)

(Eg Vs Ia)

(VL Vs IL)


19/24

Aim:

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

performance characteristics curves.

NAME PLATE DETAILS:

1 Induction Motor Auto Transformer

Fuse Rating:

125% of rated current (Full load current)

Apparatus required:

Formulae used:

1. Torque = (S1S2) (R+t/2) x 9, 81 N-m.i. S1, S2 spring balance readings in Kg.

ii. R Radius of the brake d5rum in m.

iii. T Thickness of the belt in m.

2. Output power = 2NT/60 Wattsi. N Rotor speed in rpm.

ii. T Torque in N-m.

3. Input power = W

i. W Wattmeter readings in watts.4. Percentage of efficiency = (Output power/Input power) x 100%

5. Percentage of slip = (Ns N)/Ns x 100%

i. Ns Synchronous speed in rpm.ii. N Speed of the motor in rpm.

S.No Name of the Apparatus Type Range qty

1. Ammeter MI (O-20)A 1

2. voltmeter MI (0-300)v 1

3. Capacitor Electrolytic 440V/20Mfd 1

4. Wattmeter UPF (300V,10A) 1

5. Tachometer - - 1


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6. Power factor (Cos ) = Input power/VLIL.

Precaution:

i. The autotransformer should be kept at minimum voltage position

ii. The motor is started without any load

Procedure:

1. Note down the name plate details of motor.

2. Connections are made as per the circuit diagram.3. The DPSTS is closed and the autotransformer is adjusted to obtain the rated speed.

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

5. By applying the load, for various values of current the above-mentioned readings arenoted.

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

Tabulation for load test on single phase squirrel cage induction motorMultiplication factor: ..

S.no

Load

current(IL)

Load

voltage(VL)

Input power(W)

Speedof themotor(N)

Spring balancereading

Torque(T)

(s1~s2)

(R+t/2)(9.81)

Output

power

2NT/60

Efficiency

() o/p /i/p x 100

Slip (S)

(Ns-N) /Ns x 100

Powerfactor

(cos) i/p /VLIL

Observ

ed

Actu

alS1 S2

S1~S2

Amps Volts WattsWatts

rpm Kg Kg Kg N-m Watts % %

Circuit diagram for load test of 1 induction motor

20F

TS1

(0-20A) MI

P

N

300V, 10A, UPF

LM

C V

R

~V

~A

A

C

B

(0-300V) MI

Centrifugal

switch

1, Autotransformer230V/(0-270V)

D

PS

T

Sw

i

tch

R1

R2

S1

S2

BREAK DRU

30 V, 50Hz, 1,AC Supply

R1, R2 running winding

S1, S2 Starting winding

TS1, TS2 Spring balance Reading


21/24

Observation:Circumference of the brake drum =

Thickness of the belt =

Model graph:

The graph drawn for

i. Output power Vs speedii. Output power Vs line current

iii. Output power Vs Torque

iv. Output power Vs power factorv. Output power Vs Efficiency

vi. Output power Vs %slip.

Mechanical Characteristics

Electrical Characteristics

Torque Vs Speed

Torque in N-m

Speedinrpm


22/24

MODEL CALCULATION:

RESULT:

INFERENCE:

The maximum efficiency of the induction motor

Load Test on Three - Phase Squirrel Cage Induction MotorAim:

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

performance characteristics curves.

Name plate details:

3 Induction Motor Auto Transformer

Fuse rating:

125% of rated current (Full load current)

Apparatus required:

%

%

Cos

Cos

N in rpm

Ninrpm

T in N-m

TinN-m

SlipS

IL

Out put Power in Watts

S.No Name of the Apparatus Type Range qty

1. Ammeter MI (O-10)A 1

2. voltmeter MI (0-600)v 1

3 Wattmeter UPF (500V,10A) 2

4 Tachometer - - 1


23/24

Formulae used:

1. Torque = (S1S2) (R+t/2) x 9, 81 N-m.S1, S2 spring balance readings in Kg.

R Radius of the brake d5rum in m.

T Thickness of the belt in m.

2. Output power = 2NT/60 WattsN Rotor speed in rpm.

T Torque in N-m.

3. Input power = (W1+W2) Watts

W1, W2 Wattmeter readings in watts.4. Percentage of efficiency = (Output power/Input power) x 100%

5. Percentage of slip = (Ns N)/Ns x 100%

Ns Synchronous speed in rpm.N Speed of the motor in rpm.

6. Power factor (cos ) = (W1+W2)/3 VLIL.

PRECAUTION:

i. The motor should be started without any load

PROCEDURE:

1. Note down the name plate details of motor.


3. The TPSTS is closed and the motor is started using On Linestarter to run at rated speed.

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

5. By applying the load, for various values of current the above-

mentioned readings are noted.6. The load is later released and the motor is switched off and the

graph is drawn.

OBSERVATION:

Circumference of the brake drum =

Thickness of the belt =

MODELGRAPH:


24/24

The graph drawn for

vii. Output power Vs speed

viii. Output power Vs line currentix. Output power vs. Torque

x. Output power Vs power factor

xi. Output power Vs Efficiencyxii. Output power Vs %slip.

MODEL CALCULATION:

RESULT:

INFERENCE:

The maximum efficiency of the induction motor.

TABULATION FOR LOAD TEST ON SINGLE PHASE SQUIRREL CAGE INDUCTION MOTOR

S.no Loadcurrent(IL

)

Loadvoltage(VL)

Input power(W) Speed ofthe

motor(N)

Springbalance

reading

observed actual

amps volts watts watts rpm

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EM lab for ECE