North Maharashtra University 2012 Diploma Computer Engineering MSBTEs Summer (Electrical Technology (12026)) - Question Paper
Monday, 04 February 2013 01:40Web
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12026
11122
3 Hours / 100 Marks Seat No.
Instructions - (1) All ques. are Compulsory.
(2) ans every next main ques. on a new page.
(3) Illustrate your answers with neat sketches wherever necessary.
(4) Figures to the right indicate full marks.
(5) presume 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 exam Hall.
(8) Use of Steam tables, logarithmic, Molliers chart is permitted.
Marks
1. Attempt any TEN of the following: 20
a) describe resistance. State its units.
b) describe an active network.
c) describe power factor.
d) describe an impedance. State its unit.
e) State the relation ranging from time period and frequency.
f) State the power factor of pure capacitive circuit.
g) describe phase sequence in three phase a.c. system.
h) State different losses in transformer.
i) discuss isolation transformer in brief.
j) State any 4 applications of a stepper motor.
k) State Flemings Left Hand rule.
l) discuss the necessity of fuse in the circuit.
16
2. Attempt any 4 of the following:
a) State the formulae for conversion of star into delta and delta into equivalent star network.
b) describe ideal and practical voltage sources. Represent these sources.
c) describe bilateral and unilateral networks.
d) A resistor of eight 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 eight ohm resistance and
(iv) Current through 120 ohm resistance.
e) State and discuss Kirchoffs voltage legal regulations.
f) Determine current through five ohm resistance using nodal analysis in Fig. No. 1.
3. Attempt any 4 of the following: 16
a) Draw a circuit diagram for R-L series circuit.
b) describe inductive reactance. State its unit. Show variation of inductive reactance with frequency.
c) describe active, reactive and apparent powers. Draw power triangle.
d) describe form factor and peak factor. State its values for sinusoidal a.c.
e) describe 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.
Determine:
(i) Power factor
(ii) Resistance of coil
(iii) Inductive reactance and
(iv) Inductance of coil
4. Attempt any 4 of the following: 16
a) An alternating current is represented by i= 70.7sin 520t.
Determine:
(i) frequency
(ii) r.m.s. value of current,
(iii) avg. value of current and
(iv) Current at 0.0015 2nd after passing through zero increasing positively.
b) Draw and tag the waveform of three phase e.m.f.
c) Draw the neat diagram of a 3 phase delta connected system. State relations ranging from line current and phase current, line voltage and phase voltage. Also state the relation to determine power in three phase circuit.
d) 3 identical coils every of (4.2 + j5.6) ohm are connected in star across 415 volt, three phase, 50Hz supply. Determine:
(i) Phase voltage
(ii) Line current
(iii) Power factor
(iv) Total power
e) 3 resistances of 25 ohm every are connected in delta across a three phase, 400 volt a.c.supply. obtain phase current, line current, phase voltage and line voltage.
f) Draw a neat diagram of three phase star connected system. State the relevant formulae.
5. Attempt any 4 of the following: 16
a) discuss working of a transformer.
b) Classify transformers on the basic of construction and voltage ratio.
c) State an e.m.f. formula of a transformer and state the meaning of every term used.
d) Draw a neat diagram of auto transformer. discuss 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 2 applications every of these motors.
6. Attempt any 4 of the following: 16
a) Draw a neat labelled diagram of single phase permanent capacitor induction motor. State its 2 applications.
b) State the various parts of d.c. motor. discuss any 2 parts.
c) discuss the working of d.c. motor.
d) State the kinds of single phase induction motors.
e) State the kinds of switches and sockets used in domestic installations.
f) Draw a neat labelled diagram of plate earthing.
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10 V
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| Earning: Approval pending. |
