SIR C R REDDY COLLEGE OF ENGINEERING EEE Department, ELURU.

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1 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

5 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 Total number of experiments held Total number of experiments done LAB-IN-CHARGE HEAD OF THE DEPARTMENT

7 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.

9 INDEX Sl.No. NAME OF THE EXPERIMENT Date Page No. Valued Grade

13 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 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: 1

14 TABULAR FORM: S.NO V(V) I(A) W(W) P=VI(W) %Error %Correction

15 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: 3

16 4

17 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. 5

18 TABULARFORM: S. No Voltage In Volts Current In Amps Power In Watts Time Taken For 5 Revolutions Made By Disc % Of Error % Of Correction 6

19 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. 7

20 Model Graphs: 8

21 PRECAUTIONS: RESULT: 9

22 10

23 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: S. No Apparatus Range Type Quantity 1 Ammeter MI 1 2 Voltmeter MI 1 3 Wattmeter EDW Ø load Resistive 5 3-Ø Auto Transformer 6 Connecting wires PVC Insulated THEORY: 11

24 TABULARFORM: S.NO VL IL W1 W2 P= W1+W2 Pa= 3VLILcosØ (V) (A) (W) (W) (W) (W) 12

25 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: 13

26 14

27 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: S. No Apparatus Type Range Quantity 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 Voltmeter MI Choke Coil Iron core Connecting Wires PVC Insulated THEORY: 3-Ammeter Method Power factor (cos ) = (I3 2 -(I1 2 +I2 2 ))/2I1I2 Power consumed by the inductor (PL) = (I3 2 -(I1 2 +I2 2 ))/2R 15

28 TABULAR FORM For 3-Ammeter Method: S. No Voltmeter (v) Ammeter reading(a) I1 (A) I2 (A) I3 (A) Resistance (Ω) R=V/I Power factor cos Power consumed by individual load (W) 16

From phasor diagram, we have: I3 2 =I1 2 +I2

+2V/RI2cos Hence the power, PL=VI2 cos is

2 -(I1 2 +I2 2 ))/2R Cos = (I3 2 -(I1 2 +I2 2

(cos = (v 2 -(v1 2 +v2 2 ))/ (2v1v2) Power

29 From phasor diagram, we have: I3 2 =I1 2 +I2 2 +2I1I2cos But, I1=V/R I3 2 =I1 2 +I2 2 +2V/RI2cos Hence the power, PL=VI2 cos is given by; PL=R/2( I3 2 -I1 2 -I2 2 ) PL = (I3 2 -(I1 2 +I2 2 ))/2R Cos = (I3 2 -(I1 2 +I2 2 ))/2I1I2 3-Voltmeter Method: Power factor (cos = (v 2 -(v1 2 +v2 2 ))/ (2v1v2) Power consumed by the induction = (v 2 -(v1 2 +v2 2 ))/ (2R) 17

30 TABULAR FORM for 3-Voltmeter Method: S. No. Ammeter reading(a) Voltmeter reading(v) V 1 (V) V 2 (V) V 3 (V) Power factor cos Power consumed by individual load (W) 18

31 From the phasor diagram we have V 2 =V1 2 +V2 2 +2V1V2cos =V1 2 +V2 2 +2V1(IR)cos =V1 2 +V2 2 +2R(V1Icos ) From the phasor diagram we have, V 2 =V1 2 +V2 2 +2V1V2cos =V1 2 +V2 2 +2V1(IR)cos =V1 2 +V2 2 +2R(V1Icos ) V 2 =V1 2 +V2 2 +2PR Since power in the inductive circuit, P=V1Icos = V 2 -V1 2 -V2 2 /2R P = (v 2 -(v1 2 +v2 2 ))/ (2R) cos = V 2 -V1 2 -V2 2 /2V1V2 = v 2 -(v1 2 +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 autotransformer 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. 19

32 Model Calculations: 3-Ammeter Method Power factor (cos ) = (I3 2 -(I1 2 +I2 2 ))/2I1I2 Power consumed = (I3 2 -(I1 2 +I2 2 ))/2R 3-Voltmeter Method Power factor (cos = (v 2 -(v1 2 +v2 2 ))/ (2v1v2) Power consumed by the induction = (v 2 -(v1 2 +v2 2 ))/ (2R) 20

33 PRECAUTIONS: RESULT: 21

34 22

35 MEASUREMENT OF INDUCTANCE BY ANDERSON S BRIDGE Ex. No: Date: AIM: To measure the unknown inductance by using Anderson s bridge. APPARATUS: S. No Apparatus Range Type Quantity 1 Bridge Panel Multimeter ---- Digital 1 3 Step Down Transformer Iron Core 1 4 Inductance DIB 1 5 Patch Cards and Wires PVC Insulated THEORY: 23

36 Bridge Balance Equation & Vector Diagram: 24

37 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: 25

38 26

39 MEASUREMENT OF CAPACITANCE BY SCHERING BRIDGE Ex. No: Date: AIM: To Determine the unknown capacitance by using Schering bridge. APPARATUS: S. No Apparatus Range Type Quantity 1 Bridge Panel Multimeter ---- Digital 1 3 Step Down Transformer Iron Core 1 4 Capacitor DCB 2 5 Patch Cards and Wires PVC Insulated THEORY: 27

40 Bridge Balance Condition & Vector Diagram: 28

41 PROCEDURE: 1. The circuit is designed on the bridge panel as shown in circuit diagram. 2. Switch on the power supply. 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. 5. The power supply is switched off. 6. Compare the measured value with calibrated value. PRECAUTIONS: RESULT: 29

42 30

43 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: S. No Apparatus Range Type Quantity 1 Bridge Panel Multimeter ---- Digital 1 3 Step Down Transformer Iron Core 1 4 Capacitor DCB 1 5 Patch Cards and Wires PVC Insulated THEORY: 31

44 Bridge Balance Condition and Vector Diagram: 32

45 PROCEDURE: 1. The circuit is designed on the bridge panel as shown in the circuit diagram. 2. Switch on the power supply. 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. 5. The power supply is switched off. 6. Compare measuring values with calibrated values. PRECAUTIONS: RESULT: 33

46 34

47 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: S. No Apparatus Type Range Quantity 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. 35

48 TABULARFORM: S. No Voltage Current Wattmeter-P VARMeter-Q 3-Φ Active Power 3-Φ Reactive Power (V) (A) (W) (VAR) P(KW) Q(KVAR) 36

49 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: 37

50 38

51 WEIN S BRIDGE Ex. No: Date: AIM: To measure frequency by using wein s bridge. APPARTUS: S. No Apparatus Range Type Quantity 1 Bridge Panel Multimeter ---- Digital 1 3 Function Generator 1 4 Patch Cards and Wires PVC Insulated ---- THEORY: 39

52 Bridge Balance Condition & Vector Diagram: 40

53 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: 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: 41

54 42

55 MEASUREMENT OF RESISTANCE BY WHEATSTONE BRIDGE Ex. No: Date: AIM: To determine the unknown resistance by Wheatstone bridge. APPARATUS: S. No Apparatus Range Type Quantity 1 Bridge Panel Multimeter ---- Digital 1 3 Step Down Transformer Iron Core 1 4 Patch Cards and Wires PVC Insulated ---- THEORY: 43

56 Bridge Balance Condition and Vector Diagram: 44

57 PROCEDURE: 1. The circuit is designed on the bridge panel as shown in circuit diagram. 2. Switch on the power supply. 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. 5. The power supply is switched off. 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. 4. Check for proper polarity of meters. RESULT: 45

58 46

59 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: S. No Apparatus Range Type Quantity 1. Function generators 2 2. Cathode ray oscilloscope(cro) 1 3. CRO Probes and Patch Cards ---- PVC Insulated ---- THEORY: 47

60 TABULARFORM: S. No Vertical Shape Of The Figure No.Of Tangent Points Frequency Input Frequency Fy(Hz) Horizontal Vertical Ratio Fy: Fx 48

61 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. 49

62 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 50

63 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. 51

64 52

65 CIRCUIT DIAGRAMS 53

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67 55

68 MEASUREMENT OF POWER IN AC CIRCUIT BY 3-AMMETER METHOD MEASUREMENT OF POWER IN AC CIRCUIT BY 3-AMMETER METHOD 56

69 v Electrical measurements lab manual Measurement of active and reactive power by 1-Wattmeter method 57

Bhoj Reddy Engineering College for Women, Hyderabad Department of Electronics and Communication Engineering Electrical and Electronics Instrumentation

Bhoj Reddy Engineering College for Women, Hyderabad Department of Electronics and Communication Engineering Electrical and Electronics Instrumentation Academic Year: 2016-17 III B Tech II Semester Branch: