University of Mumbai 2009-3rd Sem B.E Electrical and Electronics Engineering Electrical Measurements & Measuring Instruments - Question Paper

(3)    Figures to the right indicate full marks.

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(a)    Define limiting error. Derive an expression for relative limiting error. 0&I

(b)    Compare spring and gravity control methods of producing the deflecting Pca&Cfo torque.

(c)    Define the following terms related to the instrument transformer ' (i) Ratio error

(ii) Phase angle error.

(d)    Justify "Hay's bridge is suitable for measuring inductance of high Q. coils."

(e)    Explain how wattmeter is calibrated by using d.c. potentiometer.

2. (a) Explain the construction and working of fluxmeter. What are the advantages 10 and disadvantages ?

(b) Explain the construction, working and phasor diagram of a Maxwell-lnductance- 10 capacitance bridge for the measurement of self inductance.

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3.    (a) Explain the construction, working and theory of Ballistic galvanometer.

(b) A moving coil instrument gives a full scale deflection of 10mA when the potential

difference across its terminal is 100 mV. Calculate (i) shunt resistance for a full scale deflection corresponding to 100A. (ii) the series resistance for full scale reading with 1000 V. (iii) calculate the power dissipation in each case.

4.    (a) Explain the construction and working of single-phase Induction type

energymeter.

(b) The inductance of a moving iron Ammeter with a full scale deflection of 90 at 1-5A is given by L = {200 + 400 -4O²-0³) jiH. Where 0 is the deflection in radian from zero position. Estimate the angular deflection of the pointer for a current of 1*0A.

5.    (a) Explain the construction and working CT.

(b) Explain how iron loss is measured with Epstein Square method. Also explain its construction.

6.    Write a short notes (any two)

(a)    Rectifier type instrument

(b)    Reed type frequency meter

(c)    Weston type synchroscope.