SIR C R REDDY COLLEGE OF ENGINEERING EEE · PDF fileSIR C R REDDY COLLEGE OF ENGINEERING EEE...

EEE3110-ELECTRICAL MEASUREMENTS LAB

III/IV EEE, I Semester

SIR C R REDDY COLLEGE OF ENGINEERING

EEE Department, ELURU.

NAME: …………………………………………….

REGD.NO: …………………………………………

SECTION: …………..Academic Year: …………..

SIR.C.R.REDDY COLLEGE OF ENGINEERING

ELURU

DEPARTMENT OF

ELECTRICAL AND ELECTRONICS ENGINEERING

CERTIFICATE

This is to certify that this is the bonafide record of the work

done in ELECTRICAL MEASUREMENTS Laboratory

by Mr/Ms………………………………………………

bearing Regd. No………………………..of……………

B.Tech course during 20 - 20

Total number Total number

of experiments held……… of experiments done…………

LAB-IN-CHARGE HEAD OF THE DEPARTMENT

List of Experiments

S.No. Name of the experiment

1. Calibration of UPF wattmeter using phantom loading.

2. Calibration of energy meter using phantom loading.

3. Measurement of three-phase power using two-wattmeter method.

4. Measurement of power and power factor using 3 Ammeter method and 3

Voltmeter method.

5. Measurement of inductance by Anderson’s bridge.

6. Measurement of capacitance by Schering bridge.

7. Measurement of capacitance by De-Sauty bridge.

8. Measurement of three-phase active and reactive power by one-wattmeter

method.

9. Measurement of frequency by Wein’s bridge.

10. Measurement of resistance by Wheatstone bridge.

11. Measurement of frequency using CRO.

INDEX Sl.No. NAME OF THE EXPERIMENT Date Page

No.

Valued Grade

Electrical measurements lab manual

1

Sir CRR College Of Engineering EEE Department.

CALIBRATION OF UPF WATTMETER USING PHANTOM LOADING

Ex. No: Date:

AIM: To calibrate UPF wattmeter using Phantom loading.

APPARATUS:

S. No Apparatus Range Type Quantity

1 Ammeter MI 1

2 Voltmeter MI 2

3 1-ØAuto Transformer MI 1

4 Wattmeter Iron Core 1

5 Step-down Transformer Iron Core

6 Rheostat WW 1

7 Connecting wires ------ PVC

Insulated

--

THEORY:


2


TABULAR FORM:

S.NO V(V) I(A) W(W) P=VI(W) %Error %Correction

1

2

3

4

5

6

7

8

9

10


3


PROCEDURE:

1. Connect the circuit as shown in the diagram.

2. Close the DPST switch of high voltage supply when 1-ØAuto Transformer at zero output.

3. Apply rated voltage to pressure coil of wattmeter(c,v) using 1-ØAuto Transformer.

4. Keep rheostat in cut in position and then apply low voltage to current coil of wattmeter (m,l)

using step down transformer by closing DPST switch.

5. Vary the rheostat from 1A to rated current.

6. For each step note down the all meter readings.

7. Bring the back rheostat and 1-ØAuto Transformer to original position and open the DPST

switches.

CALCULATIONS:

% Error = ((W-P)/P) *100

%Correction = ((P-W)/P)*100

Model Graph:

PRECAUTIONS:

RESULT:


4



5


CALIBRATION OF ENERGY METER USING PHANTOM LOADING

METHOD

Ex. No: Date:

AIM: To calibrate the energy meter using phantom loading method.

APPARATUS:

S. No Apparatus Type Range Quantity

1 Single phase auto transformer Iron core 1

2 Single Phase Step Down Transformer Iron core

3 Ammeter MI 1

4 Voltmeter MI 1

5 Wattmeter EDM 1

6 Energy Meter Induction Type 1

7 Stop Watch Digital 1

8 Connecting Wires PVC Insulated ----- ----

THEORY:

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

arrangements would involve a considerable waste of power. In order to avoid this "phantom" or

'fictitious" loading is done. Phantom loading consists of supplying the pressure circuit from a

circuit required normal voltage, and the current circuit from a separate low voltage supply. it is

possible to circulate the rated current through the current circuit with a low voltage supply as the

impedance of this circuit is very low. With this arrangement the total power supplied for the test

is that due to the small pressure coil current at normal voltage, plus that due to the current circuit

current supplied at low voltage. The total power, therefore, required for testing the meter with

phantom loading is comparatively very small.


6


TABULARFORM:

S. No Voltage In

Volts

Current

In Amps

Power

In Watts

Time Taken For 5

Revolutions Made

By Disc

%

Of Error

% Of

Correction


7


PROCEDURE:

1. The connections are made as shown in the circuit diagram (1)

2. Keep the single phase auto transformer at zero output position and rheostat at

Cut in position and then close DPST switches of both HV and LV supply.

3. By varying the single phase auto transformer apply rated voltage.

4. Now by varying the rheostat in steps of 1A to up to rated current, for each step

note down the ammeter and wattmeter readings and time taken for 5 revolutions

of energy meter disc.

5. Now, bring back the rheostat to cut in position and auto transformer to zero

Position and open both DPST switches.

CREEP TEST:

1. The connections are made as shown in the circuit diagram (2).

2. Only give supply to shunt magnet of energy meter as shown in figure.

3. If the disc of energy meter rotates it is having creeping, otherwise no error.

SPECIMEN CALCULATIONS:

Energy meter constant = 1200 revolutions/KWH.

NO.OF Units recorded in energy meter for 5 revolutions Er = (1/1200) X 5 KWH.

Energy actually consumed for 5 revolutions Ea = (W/1000) X (t/ (60x60)) KWH.

Percentage Error = (Er - Ea)/Ea x100.

Percentage correction = (Ea - Er)/Ea x100.


8


Model Graphs:


9


PRECAUTIONS:

RESULT:


10



11


MEASUREMENT OF THREE-PHASE POWER USING TWO

WATTMETER METHOD.

Ex. No: Date:

AIM: To measure the 3-phase power using two wattmeter method in a balanced a.c circuit.

APPRATUS:


1 Ammeter MI 1

2 Voltmeter MI 1

3 Wattmeter EDW 2

4 3-Ø load Resistive

5 3-Ø Auto Transformer

6 Connecting wires PVC Insulated

THEORY:


12


TABULARFORM:

S.NO VL

(V)

IL

(A)

W1

(W)

W2

(W)

P= W1+W2

(W)

Pa=√3VLILcosØ

(W)


13


PROCEDURE:

1. Make the connections as per the circuit diagram.

2. Close the supply (TPST) switch, when 3-Ø auto transformer at zero output position.

3. The load is applied in steps and for each step each meter readings are noted.

4. Repeat the step 3 until the rated current of load is reached.

5. Load is removed in steps and bring back 3-Ø auto transformer to initial position and TPST

Switch is opened.

PRECAUTIONS:

RESULT:


14



15


MEASUREMENT OF POWER AND POWER FACTOR IN 1-Ø AC

CIRCUIT BY 3-AMMETER METHOD AND 3-VOLTMETER METHOD

Ex. No: Date:

AIM: To Measure Power and Power Factor by 3-Ammeter and 3-Voltmeter Method.

APPARATUS:


1. 1-ØAuto transformer Iron Core 1

2. Transformer Iron Core 1

3. Rheostat Wire wound 1

4. Voltmeter MI 1

5. Ammeter MI 1

6. Ammeter MI 1

7. Ammeter MI 1

8. Rheostat Wire wound 1

9. Voltmeter MI 1

10. Voltmeter MI 1

11. Choke Coil Iron core 1

12. Connecting Wires PVC Insulated ---- ----

THEORY:

3-Ammeter Method

Power factor (cos ) = (I32-(I1

2+I22))/2I1I2

Power consumed by the inductor (PL) = (I32-(I1

2+I22))/2R


16


TABULAR FORM

For 3-Ammeter Method:

S. No Voltmeter

(v)

Ammeter reading(A) Resistance

(Ω)

R=V/I

Power

factor

cos

Power

consumed by

individual load

(W)

I1 (A) I2 (A) I3 (A)


17


From phasor diagram, we have:

I32=I1

2+I22+2I1I2cos

But, I1=V/R

I32=I1

2+I22+2V/RI2cos

Hence the power, PL=VI2 cos is given by;

PL=R/2( I32-I1

2-I22 )

PL = (I32-(I1

2+I22))/2R

Cos = (I3

2-(I12+I2

2))/2I1I2

3-Voltmeter Method:

Power factor (cos = (v2-(v12+v2

2))/ (2v1v2)

Power consumed by the induction = (v2-(v12+v2

2))/ (2R)


18


TABULAR FORM

for 3-Voltmeter Method:

S. No.

Ammeter

reading(A)

Voltmeter reading(V) Power

factor

cos

Power consumed

by individual load

(W) V1(V) V2(V) V3(V)


19


From the phasor diagram we have

V2=V12+V2

2+2V1V2cos =V12+V2

2+2V1(IR)cos =V12+V2

2+2R(V1Icos )

From the phasor diagram we have,

V2=V12+V2

2+2V1V2cos =V12+V2

2+2V1(IR)cos =V12+V2

2+2R(V1Icos )

V2=V12+V2

2+2PR

Since power in the inductive circuit , P=V1Icos = V2-V12-V2

2/2R

P = (v2-(v12+v2

2))/ (2R)

cos = V2-V12-V2

2/2V1V2 = v2-(v12+v2

2)/ 2v1v2

PROCEDURE for 3-Ammeter Method:

1) Circuit is constructed as per circuit diagram.

2) The moving contact of the rheostat is kept at maximum resistance position and auto

transformer is at zero position.

3) Now the single phase a.c supply is given to the circuit by closing DPST Switch.

4) The rated current is made pass through the transformer in steps by varying the auto

transformer.

5) The readings of voltmeter and ammeter are tabulated and bring back auto transformer to

zero output and open DPST Switch.

PROCEDURE for 3-Volmeter Method:

1) Circuit is constructed as per circuit diagram.

2) The moving contact of the rheostat is kept at maximum resistance position and auto-

transformer is at zero position.

3) Now the single phase a.c supply is given to the circuit by closing DPST Switch.

4) Rated voltage is applied across the choke in steps by varying the auto-transformer.

5) The readings of voltmeter and ammeter are tabulated and bring back auto transformer to

zero output and open DPST Switch.


20


Model Calculations:

3-Ammeter Method

Power factor (cos ) = (I32-(I1

2+I22))/2I1I2

Power consumed = (I32-(I1

2+I22))/2R

3-Voltmeter Method

Power factor (cos = (v2-(v12+v2

2))/ (2v1v2)

Power consumed by the induction = (v2-(v12+v2

2))/ (2R)


21


PRECAUTIONS:

RESULT:


22



23


MEASUREMENT OF INDUCTANCE BY ANDERSON’S BRIDGE

Ex. No: Date:

AIM: To measure the unknown inductance by using Anderson’s bridge.

APPARATUS:


1 Bridge Panel ----- ---- 1

2 Multimeter ---- Digital 1

3 Step Down Transformer Iron Core 1

4 Inductance DIB 1

5 Patch Cards and Wires ----- PVC

Insulated

THEORY:


24


Bridge Balance Equation & Vector Diagram:


25


PROCEDURE:

1. The circuit is designed on the bridge panel as shown in the circuit diagram.

2. Switch on the power supply.

3. Now vary the variable resistors (r1,r) until the value in the multimeter shows zero value,

which is the balanced condition of the bridge.

4. The value of variable resistors at balancing condition of bridge is noted.

5. The power supply is switched off.

6. Compare the measured value with calibrated value.

PRECAUTIONS:

1. Don’t touch bare conductors when supply is ON.

2. Wear shoes in laboratory to avoid electric shocks.

3. Switch off all measuring devices when not in use.

RESULT:


26



27


MEASUREMENT OF CAPACITANCE BY SCHERING BRIDGE

Ex. No: Date:

AIM: To Determine the unknown capacitance by using Schering bridge.

APPARATUS:





4 Capacitor DCB 2


Insulated

THEORY:


28


Bridge Balance Condition & Vector Diagram:


29


PROCEDURE:

1. The circuit is designed on the bridge panel as shown in circuit diagram.


3. Now vary the variable capacitor and Resistor (C4, R4) until the value in the multimeter

shows zero voltage value i.e. the bridge is balanced.

4. The value of variable capacitor and Resistor at balancing condition of bridge is noted.


6. Compare the measured value with calibrated value.

PRECAUTIONS:

RESULT:


30



31


MEASUREMENT OF CAPACITANCE BY USING DE-SAUTY BRIDGE Ex. No: Date:

AIM: To measure the value of capacitance of a given capacitor by using De-Sauty bridge.

APPARATUS:





4 Capacitor DCB 1


Insulated

THEORY:


32


Bridge Balance Condition and Vector Diagram:


33


PROCEDURE:

1. The circuit is designed on the bridge panel as shown in the circuit diagram.


3. Now varying the variable resistor (R4) in steps until the value in the multimeter shows zero

volts i.e. bridge is balanced.

4. The value of variable resistor at balancing condition of bridge is noted.


6. Compare measuring values with calibrated values.

PRECAUTIONS:

RESULT:


34



35


MEASUREMENT OF ACTIVE AND REACTIVE POWER USING ONE

WATTMETER METHOD

Ex. No: Date:

AIM: To measure active and reactive power in three phase balanced load by one wattmeter

method.

APPARATUS:


1 3-Φ Auto Transformer Iron Core 1

2 Ammeter MI 1

3 Voltmeter MI 1

4 Wattmeter EDW 2

5 Load Box Inductive 1

6 Connecting Wires PVC Insulated _ _

THEORY:

Power in 3 phase system may be measured by using

1. Three single phase wattmeter - This method is used for a star connected, 4 wire systems,

balanced or unbalanced load.

2. Two 1 phase wattmeter - This method is suitable for 3 phase, 3 wire system and widely

used. It is applicable to both delta and star system, balanced or unbalanced load.

3. One single phase wattmeter - This method is applicable to balanced load only.

4. One 3 phase wattmeter - 3 phase wattmeter consists of two or three wattmeter elements

mounted together in one case with moving coils mounted on the same spindle

One wattmeter method for measurement of active power is for 3 phase

balanced load only. The current coil of the wattmeter is connected in one of the lines and one end

of pressure coil is connected to the same line. The readings are taken by connecting other

terminal of pressure coil alternately to other 2 lines. The active power is Ö3 times the wattmeter

reading.


36


TABULARFORM:

S. No

Voltage

(V)

Current

(A)

Wattmeter-P

(W)

VARMeter-Q

(VAR)

3-Φ Active

Power

P(KW)

3-Φ Reactive

Power

Q(KVAR)


37


It is often convenient and even essential that reactive power be measured. For example in load

monitoring, such a measurement gives the operator the information of the nature of load. Also

the reactive power serves as a check on power factor measurements, since ratio of reactive and

active power is tan f = Q/P Where Q & P are the reactive and active power respectively

One wattmeter method for measurement of reactive power is for 3 phase balanced load

only. The current coil of the wattmeter is connected in one of the lines. The pressure coil is

connected across two lines. The reactive power is 3 times the wattmeter reading.

PROCEDURE:

1. Connect the circuit as per circuit diagram.

2. Keep the inductive load at cut out position & 3-Φ Auto Transformer at zero output

position and close TPST switch.

3. Vary 3-Φ Auto Transformer up to rated voltage (say 415V)

4. Now gradually move the load in steps (say 1A to 10A) for each step note down the

ammeter, voltmeter & wattmeter reading.

5. Remove the load, bring back the 3-Φ Auto Transformer to zero output & open the TPST

switch

PRECAUTIONS:

1. Connection must be in tight

2. Where the shoes in laboratory

3. Inductive load box produce lot of noise and vibrations, so place the load in proper

position where floor is uniform.

4. Please check the auto transformer is at zero output position at closing and opening TPST

Switch.

RESULT:


38



39


WEIN’S BRIDGE

Ex. No: Date:

AIM: To measure frequency by using wein’s bridge.

APPARTUS:




3 Function Generator 1


Insulated

----

THEORY:


40


Bridge Balance Condition & Vector Diagram:


41


PROCEDURE:

1. The circuit in the panel is designed as shown in the circuit diagram.

2. Switch on the function generator with some unknown frequency.

3. Vary the variable resistors (R1 & R2) simultaneously, up to multimeter shows zero

Voltage i.e, bridge balance condition.

4. Measure the variable resistors valves at this point.

5. Turn off the power supply.

PRECAUTIONS:




RESULT:


42



43


MEASUREMENT OF RESISTANCE BY WHEATSTONE BRIDGE

Ex. No: Date:

AIM: To determine the unknown resistance by Wheatstone bridge.

APPARATUS:






Insulated

----

THEORY:


44


Bridge Balance Condition and Vector Diagram:


45


PROCEDURE:

1. The circuit is designed on the bridge panel as shown in circuit diagram.


3. Now vary the Variable resistance(S) until the value in the multimeter shows zero voltage

value i.e., the bridge is balanced.

4. The value of variable resistance at balancing condition of bridge is noted.


PRECAUTIONS:




4. Check for proper polarity of meters.

RESULT:


46



47


MEASUREMENT OF FREQUENCY USING CRO

Ex. No: Date:

AIM: To obtain Lissajous figures and to determine the ratio’s of the frequencies by using two

function generators.

APPARATUS:


1. Function generators 2

2. Cathode ray oscilloscope(CRO) 1

3. CRO Probes and Patch Cards ---- PVC Insulated ----

THEORY:


48


TABULARFORM:

S. No Vertical

Input

Frequency

Fy(Hz)

Shape Of The Figure No.Of Tangent Points Frequency

Ratio

Fy: Fx

Horizontal Vertical


49


PROCEDURE:

1. The circuit is wired as shown in figure. One signal generator is connected to the

vertical(Y) input and the other to the horizontal(X) input of the oscilloscope. The CRO

and the two generators are switched ON. The X-generator is set at 100Hz and the Y-

generator dial is used to see the stationary ellipse on the screen. The controls of CRO are

adjusted to get the ellipse of satisfactory size.

2. Leaving the horizontal(X) input at 100Hz and assuming it to be the standard, the vertical

input frequency may be varied from 100 to 900Hz to see the Lissajou’s figures. Any

number of figures can be obtained in this manner and a few of such configurations is as

shown below and frequencies ratios are determined.


50


MODEL CALCULATION:

The ratio of the two frequencies is given by:

fy / fx =

(Number of times tangent touches top or bottom)/ (Number of times tangent

touches either side)

= (number of horizontal tangents)/ (number of vertical tangents)

fy =frequency of signal applied to Y plates

fx = frequency of signal applied to X plates


51


PRECAUTIONS:

RESULT:

1. The ratios of the frequencies of the two Signals are calculated by forming Lissajou’s

figures.

2. Calculated Vertical frequencies are fy= Hz.

3. Given horizontal frequency fX= Hz.


52



53


CIRCUIT DIAGRAMS


54



55



56


MEASUREMENT OF POWER IN AC CIRCUIT BY 3-AMMETER METHOD

MEASUREMENT OF POWER IN AC CIRCUIT BY 3-AMMETER METHOD


57


Measurement of active and reactive power by 1-Wattmeter method

v

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