anderson’s bridge & schering’s bridge -...

ANDERSON’S BRIDGE & SCHERING’S BRIDGE

ANDERSON’S BRIDGE AIM: A)To measure inductance of a given coil by Anderson’s bridge.

B) To determine the value of a given capacitor and to obtain for its dissipation factor.

APPARATUS:

S.NO. Apparatus required Range Type Qty

01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

D

1KHZOscillator

BS R

1K Ohm

P1K Ohm

Q1K Ohm

LC

ANDERSON'S BRIDGE:-

D

230V50Hz

B

SR

100 Ohm - 10 Ohm

C

D

A

SCHERING BRIDGE:-

OBSERVATION TABLE:

S.NO. R2(Ω) C3 ( µ F) R1 (Ω) Cx = C3 (R1/ R2)

S.NO. P (Ω) Q (Ω) R (Ω) S (Ω) r (Ω) C(mf) L = RC(Q+2r)H

PROCEDURE: ANDERSON’S BRIDGE: 1. Connect the circuit as per circuit diagram.

2. Keep P/ Q ratio 1 and resistance in branch P should be of resistance R.

3. Now adjust the capacitance value.

4. Adjust r and S such a way to reduce sound.

5. Note down the values P, Q, R, S & r .

6. Repeat the above for different values of ‘C’.

7. Calculate self – inductance ‘L’.

SCHERING’S BRIDGE: 1. Connect the circuit show.

2. Oscilloscope is connected across points B and D.

3. The bridge is balanced by adjusting C4 and R4.

4. The readings are tabulated and C1 & r1 are calculated.

PRECAUTIONS:

1. Loose connections must be avoided.

2. In unbalanced conditions large current flows through the speaker.

3. Sound should be heard clearly where it is reducing more.

4. The readings are taken without any parallax error.

RESULT:

Viva Questions:

1) What is the application of Anderson Bridge? 2) What are the advantages and disadvantages of Schering Bridge? 3) What is the application of Schering bride? 4) What is the balancing equation in Schering Bridge? 5) Draw the phasor diagrams for the above two?

C.T. TESTING BY SILSBEE’S METHOD

C.T. TESTING BY SILSBEE’S METHOD AIM: To calibrate current transformer by using Silsbee’s method. APPARATUS:

S.NO. Apparatus required Type Range Qty

01

02

03

04

THEORY:

Circuit Diagram:

OBSERVATION TABLE:

S.NO. IP(A) I SS (A) ISX(A) ∆ I (A) W 1(W) W2(W) RX α

PROCEDURE: 1. Connect the circuit as per circuit shown.’

2. Using the auto T/ F, the current through the primary in gradually increased.

3. The difference b/ w C.T secondaries ∆ I should be zero, if it is not zero then

connection to any one of C.T secondaries are reversed .

4. The current Ip through C.T primaries is made equal to a fixed value using

auto T/F.

5. By operating the phase shifter, W1 is made zero. The readings of ammeter and

W2 are noted.

6. Now, W1 is adjusted to maximum value by rotating phase shifting T/ F and

ammeter and W2 readings are noted.

7. Above procedure is repeated for different primary current.

PRECAUTIONS:

1. Avoid loose connections.

2. Readings to be taken without parallax error.

RESULT:

Viva Questions:

1) why the C.T & P.T are called instrument transformers? 2) Why we have to close the secondary of a C.T always? 3) What are the different errors in C.T’s? 4) What is the procedure to conduct Silsbee’s method? 5) Is there any another method to test the C.T? 6) What are the advantages & disadvantages in Silsbee’s method?

CALIBRATION OF PMMC

AMMETER & VOLTMETER BY USING D.C. POTENTIOMETER

CALIBRATION OF PMMC AMMETER & VOLTMETER BY USING D.C. POTENTIOMETER

AIM: To calibrate the low range Voltmeter, Ammeter and Wattmeter by using D.C.

crampton potentiometer.

APPARATUS:


01

02

03

04

CIRCUIT DIAGRAM: Circuit is as shown in figure. THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

Calibration of Voltmeter:

Actual reading

(V)

True reading

(V) % error

Calibration of Ammeter:

Actual reading

(A)

True reading

(A) % error

PROCEDURE:

For Standardisation:

1. Connect the circuit as per circuit diagram.

2. Adjust the jockey position on the slide wire nearer to the second terminal of the

potentiometer.

3. Apply 10 V from the power supply.

4. By varying the resistance, obtain the zero deflection in the galvanometer.

5. Remove the high resistance from the circuit and again obtain the balance point in

galvanometer.

6. Now, the potentiometer is std. against the std.cell.

For Calibration of Voltmeter

1. Connect the circuit as per the circuit diagram.

2. Vary the resistance for obtaining the deflection in the voltmeter.

3. Now vary the jockey positions on the slide wire of the potentiometer and obtain

the ‘O’ deflection in the galvanometer.

4. Remove the high resistance from the circuit & obtain exact balancing point.

5. Calculate % error = 100×−readingVoltmeter

readingterPotentiomereadingVoltmeter

For Calibration of Ammeter:


2. Vary the resistance for obtaining deflection in ammeter.


zero deflection in the galvanometer.

4. Remove the high resistance from the circuit and bring obtain the exact balance

point.

5. Calculate % error = 100×−readingAmmeter

readingterPotentiomereadingAmmeter

6. Vary the resistance for different values in the Ammeter.

For Calibration of Wattmeter:


2. Vary the resistance for obtaining deflection in wattmeter.


zero deflection in the galvanometer.

4. Remove the high resistance from the circuit and obtain the exact balance point.

5. Calculate % error.

6. Vary the resistance for different values in Wattmeter.

GRAPHS:

PRECAUTIONS:

1. Connections must be tight.

2. Remove the high resistance and obtain exact balance point.

RESULT:

Viva Questions:

1) what is the classification in measuring instruments? 2) what are the different errors in PMMC instruments? 3) what are the different errors in MI instruments? 4) what is the procedure to extend the range of meters? 5) By seeing the instrument How do you identify the moving iron instruments? 6) What is the significance Crompton D.C Potentiometer?

CALIBRATION OF POWERFACTOR METER

CALIBRATION OF POWERFACTOR METER

AIM: To calibrate the given power factor meter using Inductive and Capacitive loads. APPARATUS:


01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

Voltage

(V)

Current

(A) Wattmeter (W)

Cos φ

Observed

Cos φ

(actual) Error

Tabular form when calibrating used capacitive load:

Voltage (V)

Current (A)

Wattmeter

VARS

Cos φ

Observed

Sin φ = W/ V1.

I 1

Actual Cos φ Error

PROCEDURE: 1. The circuit is connected as per the circuit diagram in fig.(1).

2. A Rheostat is connected is series with the capacitive load for the single – phase.

The supply is switched ON.

3. The Voltmeter reading is noted. The load is switched ON in steps and the

corresponding values of current, Voltage, Wattmeter and p.f are noted.

4. Now, the supply is switched OFF and is connected as in Fig. (2).

5. The supply is switched ON and steps 3 is repeated.

6. % error is calculated in both the cases.

GRAPHS:

PRECAUTIONS:

1. Loose connections are to be avoided.

2. Readings should be taken without parallax error.

3. All the connections are checked before starting the experiment.

RESULTS:

Viva Questions:

1)what is the purpose of controlling, deflecting & damping torque? 2) How do you produce the damping torque in Power factor meter? 3) why the controlling torque is not necessary in p.f meters? 4) what is the construction of p.f meter?

CALIBTATION OF WATTMETER BY PHANTOM LOADING

CALIBRATION OF WATTMETER BY PHANTOM LOADING

AIM: To calibrate the given Wattmeter by Phantom loading.

APPARATUS:


01

02

03

04

THEORY:

Circuit Diagram:

OBSERVATION TABLE:

Calibration of U.P.F. Wattmeter:

S.No. Volts (V)

Amp

(A) Watt (W) True

Value % error Correction factor

Calibration of L.P.F. Wattmeter:

S.No. Volts (V)

Amp

(A) Watt (W) True

Value % error Correction factor

PROCEDURE:


2. Apply the rated voltage to the pressure coil and low voltage to the current coil of

the Wattmeter.

3. For different values of current through the ammeter measure and record the

readings of the voltmeter and ammeter.

4. Repeat the above procedure for different values of voltage applied to the current

coil of the Wattmeter.

5. True power = VI (UPF)

= VI Cos φ (LPF)

6. Calculate % error = 100×−True

TrueActgual

7. % correction error factor = 100×−True

ActualTrue

GRAPH:

PRECAUTIONS:

1. Readings must be observed with any parallax error.


3. Junctions must be avoided at the terminals of voltmeter and ammeter.

RESULT:

Viva Questions:

1) What is the advantages of phantom loading method? 2) what is the significance of calibration of any meter? 3) what is the construction of wattmeter? 4) What are the different errors occur in wattmeter? 5) What are the different compensating techniques to reduce the errors? 6) What is the significance of multiplication factor?

CALIBRATION OF ENERGY METER

CALIBRATION OF ENERGY METER

AIM: To calibrate energy meter using wattmeter with inductive coil.

APPARATUS:


01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

S.NO. IL (A) No. of

rev t (s)

W (watt)

X4

Actual

Reading % error

PROCEDURE:

1. Connect the circuit as per the circuit shown.

2. Vary the load in steps and note down ammeter and wattmeter readings.

3. Note down the no. of revolution made of by the energy meters and note down the

time taken by using stop watch.

4. By using the energy meter constant, calculate the energy for definite no. of

revolutions .

5. % error = 100×−

i

ai

W

WW

GRAPH:

PRECAUTIONS:

1. Loose connections must be avoided.


3. Stop watch must be operate properly.

RESULT:

Viva Questions:

1) what do you mean by creeping? 2) what is meter constant? 3) What are the different errors in energy meters/ 4) what are the compensating methods to reduce the errors? 5)what is the purpose of braking magnet?

DETERMINATION OF CHOKE COIL PARAMETERS

DETERMINATION OF CHOKE COIL PARAMETERS

AIM: To determine the choke coil parameters using 3 – ammeter and 3 – voltmeter

methods.

APPARATUS:


01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLES:

S.NO. A1 (A) A2 (A) A3 (A) Cos φ R (Ω) L (H) V 1 X0 (Ω)

3 – Voltmeter Method:

S.NO. V1 (V) V2 (V) V3 (V) COS φ R (Ω) L (H) A (A) X0 (Ω)

PROCEDURE:

3 – Ammeter Method:


2. Give the supply of 1 – φ 230 V A.C, 50 Hz to variac.

3. Now, by slowly varying the variac note down different values of A1, A2 and A3.

4. Calculate Cos φ = 32

23

22

21

2 AA

AAA −−

5. Calculate the internal resistance and inductance of the choke coil.

3 – Voltmeter Method:


2. Give the supply of 230V, 50 Hz A.C. and note down the value of V1, V2 and V3

by varying the variac.

3. Calculate Cos φ = 32

23

22

21

2 VV

VVV −−

4. Calculate the internal resistance and inductance of the choke coil.

PRECAUTIONS:



3. Before switch ON supply variac position should be at same voltage.

RESULT:

Viva Questions:

1) what is the application of chock? 2) What are the parameters in this circuit? 3) Draw the phasor diagram for the two circuits? 4) What is inductance? 5) What is the significance of power factor?

MEASUREMENT OF ACTIVE POWER USING TWO C.T’S & ONE

WATTMETER

MEASUREMENT OF ACTIVE POWER USING TWO C.T’S & ONE WATTMETER

AIM: To measure the active power of a balanced load. Using single wattmeter and two

C.T’s. APPARATUS:

S.NO. Apparatus required Rating Type Qty

01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

S.NO. I1 (A) I 2 (A) I (A) V)V) W(W) W The WPral.(W)

PROCEDURE: 1. Connect the circuit as per the circuit diagram.

2. By adjusting variac, applying 3 - φ voltage to the circuit.

3. Vary the load until the ammeter gives full scale deflection.

4. Read the ammeter in the C.C of wattmeter.

5. This wattmeter reading gives active power consumed by the load.

PRECAUTIONS:


2. Avoid the parallax error.

3. Before switching ON check fuse ratings.

RESULTS:

Viva Questions:

1) How many types of powers are there? 2) What is the significance of CT? 3) Why you have to close the secondary of a C.T always? 4) What are the different errors in C.T’s? 5) What is the significance of multiplying factor in watt meters?

MEASUREMENT OF REACTIVE POWER

MEASUREMENT OF REACTIVE POWER AIM: Measuring reactive power of a 3 - φ circuit using single wattmeter. APPARATUS:


01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

S.NO. VL (V) I L (A) W (watt) √3 W √3 VLIL Sin φ

PROCEDURE:


2. Initially variac should be in minimum position .

3. Close the TPST switch on slowly vary the variac until voltmeter reads line voltage

of 415 V.

4. Now apply load in step – by – step until rated current recommended.

5. Note down the readings of Wattmeter, Voltmeter and Ammeter and tabulate.

PRECAUTIONS:



RESULT:

Viva Questions:

1) what is reactive power? 2) What are the different powers available? 3) What is the difference between balanced load & un balanced load?

MEASUREMENTS OF LOW RESISTANCE BY KELVIN’S DOUBLE BRIDGE

MEASUREMENTS OF LOW RESISTANCE BY KELVIN’S DOUBLE B RIDGE AIM: To determine the low resistance by Kelvin’s double bridge.

S.NO. ITEMS Qty Specifications

THEORY:

CIRCUIT DIAGRAM:

OBSERVATION TABLE:

Unknown Resistance – 1

S.NO. P / Q S(Ω) X = SQ

P

Unknown Resistance – 2

S.NO. P / Q S(Ω) X = SQ

P

PROCEDURE: 1. Connect the circuit as per the circuit diagram.

2. Across the terminal ‘R’ unknown resistance can be measured by ammeter.

3. The ratio P/ Q is adjusted to a particular value.

4. For this ratio, known resistance ‘S’ is varied until galvanometer shows null

deflection and obtain balance bridge conditions for different P/ Q ratio.

PRECAUTIONS:

1. Avoid loose connections.

2. Readings must be taken without parallax error.

3. At balance condition galvanometer must read zero deflection.

RESULT:

Viva Questions:

1) what are the advantages & disadvantages of Kelvin’s double bridge? 2) What is the extension in Kelvin’s double bridge? 3) What is the application of Kelvin’s double bridge?

MEASUREMENT OF CAPACITANCE BY SCHERING’S BRIDGE

MEASUREMENT OF CAPACITANCE BY SCHERING’S BRIDGE

AIM: To determine the value of a given capacitor and to obtain for its dissipation factor. APPARATUS:


01

02

03

04

THEORY:

CIRCUIT DIAGRAM:

D

230V50Hz

B

SR

100 Ohm - 10 Ohm

C

D

A

SCHERING BRIDGE:-

OBSERVATION TABLE:

S.NO. R2(Ω) C3 ( µ F) R1 (Ω) Cx = C3 (R1/ R2)

PRECEDURE:

1. Connect the circuit show.

2. Oscilloscope is connected across points B and D.

3. The bridge is balanced by adjusting C4 and R4.

4. The readings are tabulated and C1 & r1 are calculated.

PRECAUTIONS:

1. Avoid the loose connections.

2. The readings are taken without any parallax error.

RESULT:

anderson’s bridge & schering’s bridge -...

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