Maharashtra State Board of Technical Education 2011-3rd Sem Diploma Electrical Engineering (DEE) for in Electrical Engineering GroupSubject :- -Electrical Measurements(12056) - Question Pap
MSBTE ques. paper for Diploma in Electrical Engineering Group
Third Semester
Subject :- -Electrical Measurements(12056)
21011
12056
3 Hours/100 Marks Scat No
Instructions : (I) All questions are compulsory.
(2) Illustrate your answers with neat sketches wherever necessary.
(3) Figures to the right indicate full marks.
(4) Assume suitable data, if necessary.
Marks
1. Attempt any ten of the following : 20
a) Define :
1) Accuracy 2) Stability
b) State the purpose of measurement.
c) List various methods for producing damping torque in indicating instruments.
d) Define multiplying factor of wattmeter.
e) State various types of errors in wattmeters.
f) What is meant by creeping ? How it is prevented ?
g) State the working principle of induction type energy meter.
h) What is the function of synchroscope ?
i) State various applications of Q-meter.
j) Classify resistance according to their values.
k) State the factors which influence the value of earth resistance.
1) State two advantages of Kelvins double bridge over Wheat stones bridge.
2. Attempt any four of the following : 16
a) Explain magnetic effect and induction effect of electric current.
b) Classify secondary instruments depending upon the permissible percentage error.
c) Why PMMC instruments are used only for d.c. measurement ?
d) Explain the constructional details of attraction type moving won instrument with a neat diagram.
e) Explain with a neat diagram how C.T. is used for extending the range of ammeter.
f) A permanent magnet moving coil instrument gives full scale deflection of 25 mA when P.D. across its terminal is 75 mV. Calculate :
i) Resistance of shunt required for full scale deflection of 150 A.
ii) Series resistance for full scale deflection of 500 volts.
Marks
3. Attempt any four of the following : 16
a) Explain with diagram how control torque is produced by gravity control.
b) Explain with a neat sketch, working principle of dynamometer type instrument.
c) What is meant by calibration ? Draw the arrangement of calibration of a precision grade voltmeter.
d) Explain briefly error due to various methods of wattmeter connection. At what conditions these connections are used ?
e) Draw a neat labelled diagram of 3 phase dynamometer type wattmeter.
f) With the help of circuit diagram and phasor diagram, explain single wattmeter method for measurement of reactive power in a 3 phase balanced, star connected load.
4. Attempt any four of the following : 16
a) Explain briefly systematic errors taking place in measuring instrument.
b) State the advantages and limitations of digital wattmeter.
c) Explain the effect of power factor on variations in wattmeter reading in two wattmeter method.
d) Draw a neat labelled diagram of 3 phase induction type energymeter.
e) 3 phase 500 V, motor has a power factor of 0.4. The two wattmeters connected to measure the input power shows 30 kW. Find the reading of each wattmeter.
f) What is shading band ? Where it is located ? What is its purpose ?
5. Attempt any four of the following : 16
a) A 50 ampere 230 V energymeter makes 61 revolutions in 37 second. If the meter constant is 520 rev/kWh. What is the percentage error in the energymeter ?
b) With the help of block diagram, explain working electronic energy meter.
c) Explain in detail ferromagnetic type frequency meter.
d) Explain with neat diagram dynamometer type single phase power factor meter.
e) Explain with a diagram construction and working of clip on ammeter.
f) Explain in detail construction and working of rotating type phase sequence indicator.
6. Attempt any four of the following : 16
a) Draw a neat labelled diagram of Meggar.
b) Explain with diagram measurement of medium resistance using Wheatstones bridge method.
c) State various applications of digital multimeter. State its advantages.
d) Draw a neat sketch of LCR meter. Which quantities are measured by this meter ?
e) With a neat sketch, explain the constructional details of Weston synchroscope.
0 What are the drawback of shunt and multiplier ?
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