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 𝑡𝑒 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
Sl No Apparatus Specification Quantity
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:
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. 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
APPARATUS REQUIRED:-
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. Connect the circuit as in the connection diagram.
2. Check the connections and correct the mistake if any.
Sl No Apparatus Specification Quantity
1
2
3
4
5
Autotransformer
Voltmeter
Ammeter
Wattmeter
Lamp load
3. Switch on the supply
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.
5. Calculate the results accordingly.
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.
APPARATUS REQUIRED:-
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
Sl No Apparatus Specification Quantity
1
2
3
4
5
Three phase autotransformer
Voltmeter
Ammeter
Wattmeter
Rheostat
𝑺𝒊𝒎𝒊𝒍𝒂𝒓𝒍𝒚 𝑰𝑹 = 𝑰𝒀 = 𝑰𝑩 = 𝑰𝑳
𝑇𝑒𝑛 𝑡𝑒 𝑠𝑢𝑚 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑖𝑠 𝑡𝑒 𝑡𝑜𝑡𝑎𝑙 𝑝𝑜𝑤𝑒𝑟 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 𝑡𝑒 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=
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
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. Vary the autotransformer
5. Take all meter readings& tabulate
6. Verify kcl & kvl
RESULT
Verified Kirchhoff’s current law &voltage law
Sl No Apparatus Specification Quantity
1
2
3
4
Autotransformer
Voltmeter
Ammeter
Rheostat
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.
APPARATUS REQUIRED:-
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 𝑡𝑒 𝑑𝑖𝑎𝑙 𝑜𝑓 𝑤𝑎𝑡𝑡𝑚𝑒𝑡𝑒𝑟.
𝑇𝑟𝑢𝑒 𝑝𝑜𝑤𝑒𝑟 = 𝑉/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑥 𝐴/𝑚 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 ,
𝑠𝑖𝑛𝑐𝑒 𝑡𝑒 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.
Sl No Apparatus Specification Quantity
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.
Sl No Apparatus Specification Quantity
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.
APPARATUS REQUIRED:-
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
Sl No Apparatus Specification Quantity
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
APPARATUS REQUIRED:-
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
Sl No Apparatus Specification Quantity
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.
APPARATUS REQUIRED:-
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=
Sl No Apparatus Specification Quantity
1
2
3
4
Voltmeter
Ammeter
Wattmeter
Inductive coil