ELETRICAL MEASURMENT LAB-330 SEMESTER 3madinpoly.com/pdf/labmanual/3/ELECTRICAL MEASUREMENTS LAB-3… · ELETRICAL MEASURMENT LAB-330 SEMESTER 3 ... THEORY Calibration of wattmeter

ELETRICAL MEASURMENT LAB-330

SEMESTER 3

1.MEASUREMENT OF SINGLE PHASE POWER AND POWER FACTOR

USING 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.

𝐼12 = (𝐼2 + 𝐼3𝐶𝑜𝑠ø)2 + ( 𝐼3𝑆𝑖𝑛ø)2

= 𝐼22 + 𝐼3

2𝐶𝑜𝑠2ø + 2𝐼2𝐼3𝐶𝑜𝑠ø + 𝐼32𝑆𝑖𝑛2 ø

= 𝐼22 + 𝐼3

2 + 2𝐼2𝐼3 𝐶𝑜𝑠ø

Sl No Apparatus Specification Quantity

1

2

3

4

5

Ammeter

Voltmeter

Rheostat

Autotransformer

Transformer

𝑃𝐹 = ( 𝐼12 − 𝐼2

2 − 𝐼32)/2𝐼2𝐼3

𝑊𝑒 𝑕𝑎𝑣𝑒 𝑉 = 𝐼2𝑅

𝑆𝑜, 𝑃𝑜𝑤𝑒𝑟 𝐶𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 𝑡𝑕𝑒 𝑙𝑜𝑎𝑑 = 𝑉𝐼3𝐶𝑜𝑠ø

= 𝐼2𝑅 𝐼3 ( 𝐼12 − 𝐼2

2 − 𝐼32)/2𝐼2𝐼3

𝑃𝑜𝑤𝑒𝑟 = 𝑅

2 ( 𝐼1

2 − 𝐼22 − 𝐼3

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 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.

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

3

4

5

Ammeter

Voltmeter

Rheostat

Autotransformer

Transformer

We have V2= IR

So, Power Consumed by the load= V3ICosø

= ( V12-V2

2-V3

2)/2 R

Power =( V12-V2

2-V3

2)/2 R

`

PROCEDURE:




4. Adjust the autotransformer and take all meter readings.


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

4

5

Autotransformer

Voltmeter

Ammeter

Wattmeter

Lamp 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)


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.

𝑷𝒐𝒘𝒆𝒓 𝒊𝒏 𝒘𝒂𝒕𝒕𝒔 = 𝑾/𝒎 𝒙 𝑴𝒖𝒍𝒕𝒊𝒑𝒍𝒊𝒄𝒂𝒕𝒊𝒐𝒏 𝑭𝒂𝒄𝒕𝒐𝒓 𝒐𝒇 𝒕𝒉𝒆 𝑾/𝒎

𝑴𝑭

= (𝑼𝒔𝒆𝒅 𝑪𝒖𝒓𝒓𝒆𝒏𝒕 𝒓𝒂𝒏𝒈𝒆 𝒐𝒇 𝑾/𝒎 𝑿 𝒖𝒔𝒆𝒅 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝒓𝒂𝒏𝒈𝒆 𝒐𝒇 𝑾/𝒎 𝑿 𝑷𝒇 𝒐𝒇 𝑾/𝒎)

𝑴𝒂𝒙 𝒓𝒆𝒂𝒅𝒊𝒏𝒈 𝒐𝒏 𝒕𝒉𝒆 𝒅𝒊𝒂𝒍 𝒐𝒇 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓.


RESULT

Power=

Power factor=

OBSERVATION

Sl.

No

𝐴/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔

𝐴𝑚𝑝𝑠

𝑉/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔

𝑉𝑜𝑙𝑡𝑠

𝑊/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔

𝑊𝑎𝑡𝑡𝑠

𝑉𝐼

𝑃𝑜𝑤𝑒𝑟 𝑓𝑎𝑐𝑡𝑜𝑟

= (𝑊/𝑉𝐼)

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:

𝑻𝒉𝒆 𝒇𝒐𝒍𝒍𝒐𝒘𝒊𝒏𝒈 𝒎𝒆𝒕𝒉𝒐𝒅𝒔 𝒂𝒓𝒆 𝒖𝒔𝒆𝒅 𝒇𝒐𝒓 𝒕𝒉𝒆 𝒎𝒆𝒂𝒔𝒖𝒓𝒆𝒎𝒆𝒏𝒕 𝒐𝒇 𝒕 𝒉𝒆𝒓𝒆 𝒑𝒉𝒂𝒔𝒆 𝒑𝒐𝒘𝒆𝒓.

𝟏. 𝑶𝒏𝒆 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 𝒎𝒆𝒕𝒉𝒐𝒅 − 𝑭𝒐𝒓 𝒃𝒂𝒍𝒂𝒏𝒄𝒆𝒅 𝒍𝒐𝒂𝒅.

𝟐. 𝑻𝒘𝒐 𝑾𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 𝒎𝒆𝒕𝒉𝒐𝒅 – 𝑭𝒐𝒓 𝑩𝒂𝒍𝒂𝒏𝒄𝒆𝒅 / 𝑼𝒏𝒃𝒂𝒍𝒂𝒏𝒄𝒆𝒅 𝒍𝒐𝒂𝒅.

𝟑. 𝑻𝒉𝒓𝒆𝒆 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 𝒎𝒆𝒕𝒉𝒐𝒅 − 𝑭𝒐𝒓 𝑩𝒂𝒍𝒂𝒏𝒄𝒆𝒅 / 𝑼𝒏𝒃𝒂𝒍𝒂𝒏𝒄𝒆𝒅 𝒍𝒐𝒂𝒅.

Two W/m Method: - (Balanced load)

𝑳𝒆𝒕 𝒕𝒉𝒆 𝒍𝒐𝒂𝒅 𝒃𝒆 𝒂 𝟑 ø 𝒃𝒂𝒍𝒂𝒏𝒄𝒆𝒅 𝒔𝒕𝒂𝒓 𝒄𝒐𝒏𝒏𝒆𝒄𝒕𝒆𝒅 𝒐𝒏𝒆.

𝑳𝒐𝒂𝒅 𝒄𝒖𝒓𝒓𝒆𝒏𝒕 𝒕𝒉𝒓𝒐𝒖𝒈𝒉 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 𝑾𝟏 𝒊𝒔 𝑰 𝑹 𝒂𝒏𝒅. 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒂𝒄𝒓𝒐𝒔𝒔 𝒕𝒉𝒆 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒄𝒐𝒊𝒍 𝒐𝒇 𝒕𝒉𝒆 𝑾

/𝒎 𝑾𝟏 𝒊𝒔 𝑽𝑹𝒀 = 𝑽𝑹 − 𝑽𝒀

𝑹𝒆𝒂𝒅𝒊𝒏𝒈 𝒐𝒇 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 𝟏 = 𝑽𝑹𝒀𝑰 𝑹𝑪𝒐𝒔 (𝟑𝟎 + ø) = 𝑽𝑳 𝑰 𝑳𝑪𝒐𝒔 (𝟑𝟎 + ø)

𝑵𝒐𝒘 𝒄𝒖𝒓𝒓𝒆𝒏𝒕 𝒕𝒉𝒓𝒐𝒖𝒈𝒉 𝒘𝒂𝒕𝒕𝒎𝒆𝒕𝒆𝒓 − 𝟐 = 𝑰𝑩

𝑷 𝑫 𝒂𝒄𝒓𝒐𝒔𝒔 𝑾𝟐 = 𝑽𝑩𝒀 = 𝑽𝑩 − 𝑽𝒀

𝑷𝒉𝒂𝒔𝒆 𝒅𝒊𝒇𝒇𝒆𝒓𝒆𝒏𝒄𝒆 𝒃𝒆𝒕𝒘𝒆𝒆𝒏 𝑰 𝑩𝒂𝒏𝒅 𝑽𝑩𝒀 𝒊𝒔 (𝟑𝟎 − ø)

𝑹𝒆𝒂𝒅𝒊𝒏𝒈 𝒐𝒇 𝑾𝟐 = 𝑽𝑩𝒀𝑰𝑩 𝑪𝒐𝒔(𝟑𝟎 − ø)

𝑺𝒊𝒏𝒄𝒆 𝒕𝒉𝒆 𝒍𝒐𝒂𝒅 𝒊𝒔 𝒃𝒂𝒍𝒂𝒏𝒄𝒆𝒅 𝑽𝑹𝒀 = 𝑽𝑩𝒀 = 𝑽𝑩𝑹 = 𝑽𝑳


1

2

3

4

5

Three phase autotransformer

Voltmeter

Ammeter

Wattmeter

Rheostat

𝑺𝒊𝒎𝒊𝒍𝒂𝒓𝒍𝒚 𝑰𝑹 = 𝑰𝒀 = 𝑰𝑩 = 𝑰𝑳

𝑇𝑕𝑒𝑛 𝑡𝑕𝑒 𝑠𝑢𝑚 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑖𝑠 𝑡𝑕𝑒 𝑡𝑜𝑡𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 𝑡𝑕𝑒 3 ø 𝑙𝑜𝑎𝑑.

𝑾𝟏 + 𝑾𝟐 = 𝑽𝑳 𝑰𝑳 𝑪𝒐𝒔 (𝟑𝟎 − ø) + 𝑽𝑳 𝑰𝑳 𝑪𝒐𝒔 (𝟑𝟎 + ø)

= 𝑽𝑳 𝑰𝑳 [𝑪𝒐𝒔 (𝟑𝟎 − ø) + 𝑪𝒐𝒔 (𝟑𝟎 + ø)]

= 𝑽𝑳 𝑰𝑳𝟐 𝑪𝒐𝒔 𝟑𝟎 𝑪𝒐𝒔ø.

= 𝑽𝑳 𝑰𝑳 𝟐. 𝟑/𝟐.𝑪𝒐𝒔ø

= 𝟑 𝑽𝑳 𝑰𝑳𝑪𝒐𝒔ø. = 𝑬𝒒𝒖𝒂𝒕𝒊𝒐𝒏 𝒇𝒐𝒓 𝒕𝒐𝒕𝒂𝒍 𝒑𝒐𝒘𝒆𝒓 𝒊𝒏 𝒕𝒉𝒓𝒆𝒆 𝒑𝒉𝒂𝒔𝒆 𝒍𝒐𝒂𝒅.

𝑾𝟏 − 𝑾𝟐 = 𝑽𝑳 𝑰𝑳 𝑪𝒐𝒔 (𝟑𝟎 − ø) − 𝑽𝑳 𝑰𝑳 𝑪𝒐𝒔 (𝟑𝟎 + ø)

= 𝑽𝑳 𝑰𝑳 [𝑪𝒐𝒔 (𝟑𝟎 − ø) − 𝑪𝒐𝒔 (𝟑𝟎 + ø)]

= 𝑽𝑳 𝑰𝑳 𝟐. 𝑺𝒊𝒏 𝟑𝟎.𝑺𝒊𝒏ø

= 𝟐. 𝟏/𝟐. 𝑽𝑳 𝑰𝑳 . 𝑺𝒊𝒏ø

= 𝑽𝑳 𝑰𝑳 . 𝑺𝒊𝒏ø

𝑾𝟏− 𝑾𝟐

𝑾𝟏+ 𝑾𝟐 =

𝑽𝑳 𝑰𝑳 .𝑺𝒊𝒏ø

3𝑽𝑳 𝑰𝑳𝑪𝒐𝒔ø =

1

3tan

= 𝐭𝐚𝐧−𝟏[ 𝟑(𝑾𝟏− 𝑾𝟐𝑾𝟏+ 𝑾𝟐

)]

𝑯𝒆𝒏𝒄𝒆 𝒑𝒐𝒘𝒆𝒓 𝒇𝒂𝒄𝒕𝒐𝒓 𝒄𝒐𝒔 𝒄𝒂𝒏 𝒃𝒆 𝒄𝒂𝒍𝒄𝒖𝒍𝒂𝒕𝒆𝒅.

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 𝑻𝒂𝒏

𝒄𝒐𝒔

CIRCUIT DIAGRAM

5. VERIFICATION OF KCL&KVL

AIM

To verify KCL&KVL in dc circuits

APPARATUS REQUIRED

THEORY

𝑲𝑰𝑹𝑪𝑯𝑶𝑭𝑭’𝒔 𝒄𝒖𝒓𝒓𝒆𝒏𝒕 𝒍𝒂𝒘(𝑲𝑪𝑳)

𝑰𝒕 𝒔𝒕𝒂𝒕𝒆𝒔 𝒕𝒉𝒂𝒕 𝒂𝒍𝒈𝒆𝒃𝒓𝒂𝒊𝒄 𝒔𝒖𝒎 𝒐𝒇 𝒕𝒉𝒆 𝒄𝒖𝒓𝒓𝒆𝒏𝒕 𝒎𝒆𝒆𝒕𝒊𝒏𝒈 𝒂𝒕 𝒂𝒏𝒚 𝒋𝒖𝒏𝒄𝒕𝒊𝒐𝒏 𝒊𝒔 𝒛𝒆𝒓𝒐.

Ʃ𝑰 = 𝟎

𝑲𝑰𝑹𝑪𝑯𝑶𝑭𝑭’𝒔 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒍𝒂𝒘(𝑲𝒗𝑳)

𝑰𝒕 𝒔𝒕𝒂𝒕𝒆𝒔 𝒕𝒉𝒂𝒕 𝒊𝒏 𝒂𝒄𝒍𝒐𝒔𝒆𝒅 𝒎𝒆𝒔𝒉,𝒂𝒍𝒈𝒆𝒃𝒓𝒂𝒊𝒄 𝒔𝒖𝒎 𝒐𝒇 𝒕𝒉𝒆 𝒗𝒐𝒍𝒕𝒂𝒈𝒆 𝒅𝒓𝒐𝒑 𝒊𝒏 𝒓𝒆𝒔𝒊𝒔𝒕𝒐𝒓𝒔 𝒂𝒏𝒅 𝒆𝒎𝒇’𝒔 𝒆𝒒𝒖𝒂𝒍 𝒕𝒐 𝒛𝒆𝒓𝒐

𝑰𝒆,Ʃ𝑰𝑹 + Ʃ𝑬𝑴𝑭𝒔 = 𝟎

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).

𝑅𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 = 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑥 𝑚𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟.

𝑀𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟

= 𝑆𝑒𝑙𝑒𝑐𝑡𝑒𝑑 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑟𝑎𝑛𝑔𝑒 𝑜𝑓 𝑊/𝑚 𝑥 𝑆𝑒𝑙𝑒𝑐𝑡𝑒𝑑 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑟𝑎𝑛𝑔𝑒 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟 𝑥 𝑃𝐹

𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑜𝑛 𝑡𝑕𝑒 𝑑𝑖𝑎𝑙 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟.

𝑇𝑟𝑢𝑒 𝑝𝑜𝑤𝑒𝑟 = 𝑉/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑥 𝐴/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 ,

𝑠𝑖𝑛𝑐𝑒 𝑡𝑕𝑒 𝑙𝑜𝑎𝑑 𝑢𝑠𝑒𝑑 𝑖𝑠 𝑝𝑢𝑟𝑒𝑙𝑦 𝑟𝑒𝑠𝑖𝑠𝑡𝑖𝑣𝑒, 𝑖𝑡𝑠 𝑝𝑓 𝑖𝑠 𝑢𝑛𝑖𝑡𝑦.

%𝑒𝑟𝑟𝑜𝑟 =𝑟𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 − 𝑡𝑟𝑢𝑒 𝑝𝑜𝑤𝑒𝑟

𝑟𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑝𝑜𝑤𝑒𝑟× 100

PROCEDURE

1. Connect the circuit as shown in figure

2. Checked the connections and given the supply.


1

2

3

4

Voltmeter

Ammeter

Wattmeter

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 𝐴/ 𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔− 𝐴𝑚𝑝𝑠

𝑉/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 −𝑉𝑜𝑙𝑡𝑠

𝑊/𝑚− 𝑊𝑎𝑡𝑡𝑠

𝑅𝑒𝑐. 𝑃𝑜𝑤𝑒𝑟 𝑊𝑎𝑡𝑡𝑠 𝑇𝑟𝑢𝑒 𝑝𝑜𝑤𝑒𝑟 𝑊𝑎𝑡𝑡𝑠

% 𝐸𝑟𝑟𝑜𝑟

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

𝑻𝒖𝒓𝒏𝒔 𝒓𝒂𝒕𝒊𝒐 𝒐𝒇 𝒂 𝒕𝒓𝒂𝒏𝒔𝒇𝒐𝒓𝒎𝒆𝒓 = 𝑵𝒐 𝒐𝒇 𝒕𝒖𝒓𝒏𝒔 𝒐𝒇 𝒑𝒓𝒊𝒎𝒂𝒓𝒚/𝑵𝒐 𝒐𝒇 𝒕𝒖𝒓𝒏𝒔 𝒐𝒇 𝒔𝒆𝒄𝒐𝒏𝒅𝒂𝒓𝒚.

𝑻𝒓𝒂𝒏𝒔𝒇𝒐𝒓𝒎𝒂𝒕𝒊𝒐𝒏 𝒓𝒂𝒕𝒊𝒐 𝑲 = 𝑺𝒆𝒄𝒐𝒏𝒅𝒂𝒓𝒚 𝒊𝒏𝒅𝒖𝒄𝒆𝒅 𝑬𝑴𝑭/ 𝑷𝒓𝒊𝒎𝒂𝒓𝒚 𝒊𝒏𝒅𝒖𝒄𝒆𝒅 𝑬𝑴𝑭 = 𝑬𝟐/𝑬𝟏

𝑬𝟏 = 𝟒.𝟒𝟒𝟒 𝝋𝒎.𝒇. 𝑵𝟏𝑽𝒐𝒍𝒕𝒔. , 𝑨𝒏𝒅 𝑬𝟐 = 𝟒. 𝟒𝟒𝟒 𝝋𝒎.𝒇. 𝑵𝟐𝑽𝒐𝒍𝒕𝒔 ,𝑲 = 𝑬𝟐/𝑬𝟏

𝑲 = 𝟒. 𝟒𝟒𝟒 𝝋𝒎.𝒇. 𝑵𝟐/ 𝟒.𝟒𝟒𝟒 𝝋𝒎.𝒇.𝑵𝟏 = 𝑵𝟐/𝑵𝟏

𝑻𝒖𝒓𝒏𝒔 𝒓𝒂𝒕𝒊𝒐, 𝑵𝟏/𝑵𝟐 = 𝑬𝟏/𝑬𝟐

𝑵𝒐 𝒍𝒐𝒂𝒅 𝒊𝒏𝒑𝒖𝒕 𝒑𝒐𝒘𝒆𝒓, 𝑾𝟎 = 𝑽𝟎 𝑰𝟎 𝑪𝒐𝒔𝝋𝟎, 𝑪𝒐𝒔𝝋𝟎 = 𝑾𝟎/ 𝑽𝟎 𝑰𝟎, 𝝋𝟎 = 𝒄𝒐𝒔−𝟏(𝑾𝟎/ 𝑽𝟎 𝑰𝟎)

𝑴𝒂𝒈𝒏𝒆𝒕𝒊𝒛𝒊𝒏𝒈 𝒄𝒐𝒎𝒑𝒐𝒏𝒆𝒏𝒕 𝒐𝒇 𝒏𝒐 𝒍𝒐𝒂𝒅 𝒄𝒖𝒓𝒓𝒆𝒏𝒕 𝑰𝝁 = 𝑰𝟎 𝑺𝒊𝒏𝝋𝟎

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

4

5

Voltmeter

Ammeter

Wattmeter

Transformer

autotransformer

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 𝑅𝑋 be the number

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

Recorded energy=𝑅𝑋 𝐾𝑋 𝐾𝑊𝐻

The true energy=𝑤/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 ∗ 𝑡𝑖𝑚𝑒

%error= (𝑟𝑒𝑐𝑜𝑟𝑑𝑒𝑑 𝑒𝑛𝑒𝑟𝑔𝑦 − 𝑡𝑟𝑢𝑒 𝑒𝑛𝑒𝑟𝑔𝑦)/𝑡𝑟𝑢𝑒 𝑒𝑛𝑒𝑟𝑔𝑦 × 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

2

3

4

5

Voltmeter

Ammeter

Wattmeter

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 in

volt

A/m in

amps

No. of

rev

w/m in

watts

Time in

sec

True

energy

Actual

energy

%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 supplying

the 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

2

3

4

Voltmeter

Ammeter

Wattmeter

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 of

E/M disc

Recorded

power=

5

𝑡×

3600

𝑁

KWH

Actual

power

𝑉𝐼 cos ∅/1000

Error

𝑅𝑃 − 𝐴𝑃

%error= 𝑅𝑃 − 𝐴𝑃

𝑅𝑃

UPF

0.5

LAG

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 = 𝒁𝟐 − 𝑹𝟐

But XL=2πfL

I.e., L= 𝑋𝐿

2𝜋𝑓

Power factor of the coil=𝑃 𝑉𝐼

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 readings

5. 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/I R=

𝑃

𝐼2

XL

= 𝑍2 − 𝑅2

L=

XL 2𝜋𝑓

Pf= 𝑃

𝑉𝐼

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