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Posted Date: 21 Jun 2012 Posted By:: Anurag A. Sonawane Member Level: Bronze Points: 5 (Rs. 1)
2012 North Maharashtra University Diploma Computer Engineering MSBTEs Summer 2012 Examination (Electrical Technology (12026)) Question paper
this is MSBTEs Summer 2012 Examination (Electrical Technology (12026)) question paper.
3 Hours / 100 Marks Seat No.
Instructions - (1) All Questions are Compulsory.
(2) Answer each next main Question on a new page.
(3) Illustrate your answers with neat sketches wherever necessary.
(4) Figures to the right indicate full marks.
(5) Assume suitable data, if necessary.
(6) Use of Non-programmable Electronic Pocket Calculator is permissible.
(7) Mobile Phone, Pager and any other Electronic Communication devices are not permissible in Examination Hall.
(8) Use of Steam tables, logarithmic, Molliers chart is permitted.
1. Attempt any TEN of the following: 20
a) Define resistance. State its units.
b) Define an active network.
c) Define power factor.
d) Define an impedance. State its unit.
e) State the relation between time period and frequency.
f) State the power factor of pure capacitive circuit.
g) Define phase sequence in 3 phase a.c. system.
h) State various losses in transformer.
i) Explain isolation transformer in brief.
j) State any four applications of a stepper motor.
k) State Flemings Left Hand rule.
l) Explain the necessity of fuse in the circuit.
2. Attempt any FOUR of the following:
a) State the formulae for conversion of star into delta and delta into equivalent star network.
b) Define ideal and practical voltage sources. Represent these sources.
c) Define bilateral and unilateral networks.
d) A resistor of 8 ohm is connected in series with a combination of 12 ohm and 24 ohm in parallel. A 100 volt d.c. supply is connected across the combination. Determine.
(i) Equivalent resistance of the circuit,
(ii) Total current,
(iii) Voltage across 8 ohm resistance and
(iv) Current through 120 ohm resistance.
e) State and explain Kirchoffs voltage law.
f) Determine current through 5 ohm resistance using nodal analysis in Fig. No. 1.
3. Attempt any FOUR of the following: 16
a) Draw a circuit diagram for R-L series circuit.
b) Define inductive reactance. State its unit. Show variation of inductive reactance with frequency.
c) Define active, reactive and apparent powers. Draw power triangle.
d) Define form factor and peak factor. State its values for sinusoidal a.c.
e) Define cycle, amplitude, time period and frequency.
f) A choke coil takes a current of 2.5 ampere, when connected across 250volt, 50Hz a.c. supply and consumes 400 watt.
(i) Power factor
(ii) Resistance of coil
(iii) Inductive reactance and
(iv) Inductance of coil
4. Attempt any FOUR of the following: 16
a) An alternating current is represented by i= 70.7sin 520t.
(ii) r.m.s. value of current,
(iii) average value of current and
(iv) Current at 0.0015 second after passing through zero increasing positively.
b) Draw and label the waveform of 3 phase e.m.f.
c) Draw the neat diagram of a three phase delta connected system. State relations between line current and phase current, line voltage and phase voltage. Also state the relation to determine power in 3 phase circuit.
d) Three identical coils each of (4.2 + j5.6) ohm are connected in star across 415 volt, 3 phase, 50Hz supply. Determine:
(i) Phase voltage
(ii) Line current
(iii) Power factor
(iv) Total power
e) Three resistances of 25 ohm each are connected in delta across a 3 phase, 400 volt a.c.supply. Find phase current, line current, phase voltage and line voltage.
f) Draw a neat diagram of 3 phase star connected system. State the relevant formulae.
5. Attempt any FOUR of the following: 16
a) Explain working of a transformer.
b) Classify transformers on the basic of construction and voltage ratio.
c) State an e.m.f. equation of a transformer and state the meaning of each term used.
d) Draw a neat diagram of auto transformer. Explain its working. State its applications.
e) A 200kVA, 3300/240V, 50Hz single phase transformer has 80 turns on secondary winding. Calculate:
(i) Primary and secondary currents on full load
(ii) Max. value of flux and
(iii) Number of primary turns.
f) Represent D.C. shunt and series motors. State any two applications each of these motors.
6. Attempt any FOUR of the following: 16
a) Draw a neat labelled diagram of single phase permanent capacitor induction motor. State its two applications.
b) State the different parts of d.c. motor. Explain any two parts.
c) Explain the working of d.c. motor.
d) State the types of single phase induction motors.
e) State the types of switches and sockets used in domestic installations.
f) Draw a neat labelled diagram of plate earthing.
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