ELECTRICAL MEASUREMENTS LAB-330.pdf

7/24/2019 ELECTRICAL MEASUREMENTS LAB-330.pdf

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ELETRICAL MEASURMENT LAB-330

SEMESTER 3

1.MEASUREMENT OF SINGLE PHASE POWER AND POWER FACTORUSING THREE AMMETERS.

AIM

To measure the power and power factor of the given R-L circuit using three Ammeters.

(Without using Wattmeter)

APPARATUS REQUIRED:-

THEORY

Power factor is the cosine of the angle between phase voltage and current. The maximum

value of power factor is unity, i.e. for pure resistive load and minimum value is zero.ie for pure

inductive load (lagging) or pure capacitive load (leading).

For an R-L circuit, the current lags voltage by certain angle, which is called the power

factor angle ø.

The vector diagram is shown in figure. Voltage V is taken as the reference, I2is in phase

with V (since current through pure resistance- in phase with V,), I3 lags behind V by angle ø,(since R-L circuit), I1 is the vector sum of I2 and I3.

12 = (2 + 3ø)2 + ( 3ø)2

= 22 + 3

22ø + 223ø + 322 ø

= 22 + 3

2 + 223 ø

Sl No Apparatus Specification Quantity

1

2

34

5

Ammeter

Voltmeter

RheostatAutotransformer

Transformer



= ( 12 − 2

2 − 32)/223

= 2

, = 3ø

= 2 3 ( 12 − 2

2 − 32)/223

= 2 ( 1

2 − 22 − 3

2)

PROCEDURE:

1.

Connect the circuit as in the connection diagram.

2. Check the connections and correct the mistake if any.

3. Switch on the supply

4. First note the reading in the Voltmeter, then gradually increase the input voltage and take

the corresponding readings in all the three meters. Tabulate.

5.

Calculate the results accordingly.

RESULT

Power = Power factor =



OBSERVATION

Sl No V/m

Reading-

Volts

I1

Amps

I2

Amps

I3

Amps

Power=

R/2(I12-I2

2-I3

2)

PF=

(I12-I2

2-I3

2)/2 I2I3

CIRCUIT DIAGRAM



2.MEASUREMENT OF SINGLE PHASE POWER AND POWER FACTOR

USING THREE VOLTMETERS.

AIM

To measure the power and power factor of the given R-L circuit using three voltmeters.

(Without using Wattmeter)

APPARATUS REQUIRED

THEORY

Power factor is the cosine of the angle between phase voltage and current. The maximum valueof power factor is unity, i.e. for pure resistive load and minimum value is zero.ie for pure

inductive load (lagging) or pure capacitive load (leading).

For an R-L circuit, the current lags voltage by certain angle, which is called the power factor

angle ø.

The vector diagram is shown in figure. Voltage V is taken as the reference, I2is in phase with V (

since current through pure resistance- in phase with V,), I3 lags behind V by angle ø, (since R-L

circuit), I1 is the vector sum of I2 and I3.

V12= (V2+V3Cosø)2+ ( V3Sinø)2

= V22+V3

2Cos

2ø+2V2V3Cosø+V3

2Sin

2 ø

= V22+V3

2+2 V2V3 Cosø

... PF=( V1

2-V2

2-V3

2)/2 V2V3


1

2

34

5

Ammeter

Voltmeter

RheostatAutotransformer

Transformer



We have V2= IR

So, Power Consumed by the load= V3ICosø

= ( V12-V2

2-V3

2)/2 R

Power =( V12-V2

2-V32)/2 R

`

PROCEDURE:

1. Connect the circuit as in the connection diagram.



4. Adjust the autotransformer and take all meter readings.

5. Calculate the results accordingly.

RESULT



Power = Power factor =

OBSERVATION

Sl No V/m

Reading-

Volts

V1

Amps

V2

Amps

V3

Amps

Power=

(V12-V2

2-V3

2)/2R

PF=

(V12-V2

2-

V32)/2V2V3

CIRCUIT DIAGRAM



3. SINGLE PHASE POWER MEASUREMENT BY USING WATTMETER

AIM

To measure the single phase power consumed by the load using a wattmeter and to calculate the

power factor


THEORY

Electric power is the rate at which electric energy is transferred by an electric circuit.

The SI unit of power is the watt. there are three types of ac power

Apparent power

It is the product of RMS value of applied voltage and current. S = VI KVA

Active power

It the power actually consumed in a ac circuit. P = V Icos ø KW

Reactive power

This power is due to the reactance of the circuit. Q = VIsin ø KVAR

By wattmeter method the active power of the circuit is measured.

PROCEDURE




1

2

3

45

Autotransformer

Voltmeter

Ammeter

WattmeterLamp load

https://en.wikipedia.org/wiki/Electric_energy

https://en.wikipedia.org/wiki/Electric_circuit

https://en.wikipedia.org/wiki/SI

https://en.wikipedia.org/wiki/Power_(physics)

https://en.wikipedia.org/wiki/Watt_(unit)

https://en.wikipedia.org/wiki/Watt_(unit)

https://en.wikipedia.org/wiki/Power_(physics)

https://en.wikipedia.org/wiki/SI

https://en.wikipedia.org/wiki/Electric_circuit

https://en.wikipedia.org/wiki/Electric_energy




4. First note the reading in the Voltmeter, then one by one increase the load and take the

corresponding readings in all the meters. Tabulate them.

= / /

= ( / / /)

.

5. Calculate the results accordingly.

RESULT

Power=

Power factor=



OBSERVATION

Sl.

No

/

/

/

= (/)

CIRCUIT DIAGRAM



4. MEASUREMENT OF THREE PHASE POWER AND POWER FACTOR USING

TWO WATTMETERS

AIM

To measure the input power and determine power factor of a balanced three phase load using two

W/ms.


THEORY:

.. − .

. – / .

. − / .

Two W/m Method: - (Balanced load)

ø .

.

/ = −

= ( + ø) = ( + ø)

− =

= = −

( − ø)

= ( − ø)

= = =


1

2

34

5

Three phase autotransformer

Voltmeter

AmmeterWattmeter

Rheostat



= = =

3 ø .

+ = ( − ø) + ( + ø)

= [ ( − ø ) + ( + ø)]

=

ø.

= . /. ø

= ø. = .

− = ( − ø) − ( + ø)

= [ ( − ø) − ( + ø)]

= . . ø

= . /. . ø

= . ø

−

+ =

.

ø

3 ø =1

3tan

= −[ (− +

)]

.

PROCEDURE

1. Connections are made as shown in the circuit diagram

2. Keep the autotransformer at minimum position

3. Adjust the autotransformer till the voltmeter reads 400v

4. Take the corresponding v/m, a/m and w/m readings.

5. Tabulate the readings and calculate the power and power factor

RESULT:

Power=

Power factor=



OBSERVATION

Sl no V I W1 W2 W1+W2 W2-W1

CIRCUIT DIAGRAM



5. VERIFICATION OF KCL&KVL

AIM

To verify KCL&KVL in dc circuits

APPARATUS REQUIRED

THEORY

’ ()

.

Ʃ =

’ ()

, ’

,Ʃ + Ʃ =

PROCEDURE




4. Vary the autotransformer

5.

Take all meter readings& tabulate

6. Verify kcl & kvl

RESULT

Verified Kirchhoff’s current law &voltage law


1

2

3

4

Autotransformer

Voltmeter

Ammeter

Rheostat



OBSERVATION

Sl no V1 V2 V3 V2+V3 I1 I2 I3 I2+I3

CIRCUIT DIAGRAM



6. CALIBRATION OF WATTMETER USING VOLTMETER AND AMMETER.

AIM

To calibrate the given single phase wattmeter using standard voltmeter and ammeter. Draw the

Calibration and error curves.


THEORY

Calibration of wattmeter means standardizing of meter and finding out the error. A

wattmeter is a device that is constructed out of pressure coil and current coil. The pressure coil is

connected in parallel with the circuit, and current coil in series with the circuit. The current coil

has low resistance connected in series with the ammeter.

There are Induction type (used in AC measurements only) and Dynamometer type

wattmeter (used in both AC & DC measurements).

= .

= /

.

= / / ,

, .

% = −

× 100

PROCEDURE

1. Connect the circuit as shown in figure

2. Checked the connections and given the supply.


1

23

4

Voltmeter

AmmeterWattmeter

Lamp load



3. Varied the load and taken the corresponding readings.

4. Calculated the true power, recorded power and % error at the different loads.

5. Plotted the graphs of true power Vs recorded power and % error Vs recorded power.

RESULT: Plotted the graphs of recorded power Vs true power and % error Vs recorded power.



OBSERVATION

CIRCUIT DIAGRAM

Sl

No /

−

/

−

/

−

.

%



8. POLARITY TEST AND TURN`S RATIO TEST ON SINGLE PHASE TRANSFORMER

AIM:

To conduct polarity test, and determine turn`s ratio, transformation ratio, and magnetizing component of

No Load current of single phase transformer

APPARATUS

THEORY

= / .

= / = /

= . . . . , = . . . , = /

= . . . / . . . = /

, / = /

, = , = / , = −(/ )

=

PROCEDURE

1) Polarity test.

1. Connections are made as shown in figure (1)

2. Checked the connections and given a specified voltage to primary.

3. Noted the volt meter reading and verified the polarity of the transformer.ie If the

voltmeter reading in the inter connected voltmeter is greater than the input voltage, and

then the polarity is additive, So Opposite polarity on the other adjacent terminal on

secondary.


1

2

3

45

Voltmeter

Ammeter

Wattmeter

Transformerautotransformer



4. Interchanged the connections to confirm first determined polarity.

Turn`s ratio and transformation ratio;

1.

Connections are made as in figure (2)

2. Checked the connections and given the supply gradually from minimum voltage to rated

voltage of primary using autotransformer.

3. Noted the V/m readings on primary and secondary and the A/m and W/m reading when

applying the rated primary voltage.

4. Calculate the turn’s ratio of the transformer

RESULT

Checked the polarity and determined the turn’s ratio transformation ratio, and magnetizing

component of no load current of 115/220V, 1 KVA transformers.

Turns ratio= Transformation ratio=



OBSERVATION

Sl No

Prim. V/m

reading E1

Sec. V/m

reading E2

Watt meter

reading W0

A/m

reading I0

Turns ratio Transf.

ratio =K

CIRCUIT DIAGRAM



9. ENERGY METER CALIBRATION BY DIRECT LOADING

AIM

To calibrate the energy meter by direct loading.


THEORY

The process of comparing of an instrument with standard or absolute instrument is called

calibration. The energy meter records the energy consumed in KWH. Let be the number

of revolutions of the disc. Is the revolution per KWH (meter constant).

Recorded energy=

The true energy=/ ∗

%error=( − )/ × 100

PROCEDURE

1. Connections are made as per the circuit diagram

2. Keep the autotransformer at minimum position and switch on the supply

3. Adjust the autotransformer to the rated voltage of the energy meter

4. Adjust the load to a suitable value and note the corresponding w/m reading and time

taken for 5 revolution of energy meter disc

5. Repeat the step no 4 after increasing the load

6. Tabulate the readings and calculate the %error

RESULT


1

23

4

5

Voltmeter

AmmeterWattmeter

Lamp load

Energy meter



Calibrated the given single phase energy meter by direct loading at UPF and plotted the error

curve

OBSERVATION

Sl no v/m involt

A/m inamps

No. ofrev

w/m inwatts

Time insec

Trueenergy

Actualenergy

%error

CIRCUIT DIAGRAM



10. CALIBRATION OF WATTMETER BY PHANTOM LOADING

AIM

To calibrate the given single phase wattmeter by phantom loading at UPF and at 0.5pf


THEORY

When current rating of the meter under test is high, a test with actual loading

arrangements involves considerable waste of power. Phantom loading consists of supplyingthe pressure circuit with required normal voltage and the current circuit from a low voltage

supply. the total power required for testing the meter with phantom loading is comparatively

very small.

PROCEDURE

At UPF

1. Connections are made as shown in diagram

2. The rated voltage applied across pressure coil

3.

Keep the autotransformer at its minimum position and switch on the power supply.4. Adjust the autotransformer for various values of current from minimum to maximum

5. Take all meter readings and time taken for 5revolution of E/M disc

6. Plot error and calibration curve

At 0.5pf lag

1. Connect the pressure coil across N&Y and CC in R phase


1

23

4

Voltmeter

AmmeterWattmeter

Lamp load



2. Repeat the same procedure mentioned above

3. Plot the error and calibration curve

RESULT

The given single phase energy meter is calibrated at UPF and 0.5 lag by phantom loading



OBSERVATION

PF v/m A/m Time for

5rev ofE/M disc

Recorded

power=

5

×

3600

KWH

Actual

power

cos ∅/1000

Error

−

%error= −

UPF

0.5LAG



11. MEASUREMENT OF INDUCTANCE USING WATTMETER

AIM

To measure the inductance and power factor of the given coil.


THEORY

Inductance is the property of a circuit or a component to oppose the change in current

through it. An induction coil has a small resistance and an inductive reactance.

XL = −

But XL=2πfL

I.e., L= 2

Power factor of the coil=

PROCEDURE

1.

Connections are made as shown in diagram

2. Keep the autotransformer in the minimum position and switch on the supply

3. Adjust the autotransformer into rated voltage

4.

Note all meter readings5. Tabulate the reading and calculate the inductance and pf of the coil

RESULT

Inductance=

Power factor=


1

2

3

4

Voltmeter

Ammeter

Wattmeter

Inductive coil



OBSERVATION

Sl no V/m A/m W/m Z=V/IR=

2

XL

=2 − 2

L=

XL 2

Pf=

ELECTRICAL MEASUREMENTS LAB-330.pdf

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