Jawaharlal Nehru Technological University Kakinada 2008 B.Tech Electronics and Communications Engineering electrical technology - Question Paper

a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm.
To what induced voltage must the alternator be excited if it is to deliver a
load of 100 A at a pf of 0.8 lagging, with a terminal voltage of 200 V. [8+8]
7. (a) discuss why the value of motor time constant is zero on no-load of a servo
motor.
(b) A capacitive begin motor does not run when the breaker is closed; It hums
loudly and begins to smoke. If the breaker is closed while the shaft is rotated by
hand however the machine comes up to speed and operates properly. discuss
the probable faults.
[16]
8. (a) discuss the working of attracted disc kind voltmeter with neat sketch. [8+8]
(b) How will you use a PMMC instrument which provide full scale de?ection at 50
mV p.d. and 10 mA current as
i. Ammeter: 0-10A range
ii. Voltmeter: 0-250V range.
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2 of 2Code No: 07A3EC13 Set No. 2
II B.Tech I Semester Regular Examinations, November 2008
ELECTRICAL TECHNOLOGY
( Common to Electronics & Communication Engineering, Electronics &
Instrumentation Engineering, Bio-Medical Engineering, Electronics &
Control Engineering, Electronics & Telematics, Electronics & Computer
Engineering and Instrumentation & Control Engineering)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
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1. (a) Develop from ?rst principles an expression for the emf of a dc generator.
(b) The wave connected armature of a 4 pole dc generator is needed to gen-
erate an emf of 520V when driven at 600 rev/min. compute the ?ux per pole
needed if the armature has 144 slots with 2 coil sides per slot, every coil
consisting of three turns. [8+8]
2. (a) discuss the internal and external characteristics of dc shunt motor.
(b) Why starter is necessary for an operation of dc motor? Also discuss the
di?erent protective devices used in three - point starter. [6+10]
3. (a) discuss with a neat sketches the constructional details of:
i. core kind transformer and
ii. shell kind transformer
(b) The primary winding of a 50Hz single phase transformer has 500 turns and is
supplied from 3300V supply. The secondary winding has 50 turns. obtain peak
value of the ?ux in the core and the secondary voltage. [8+8]

Earning:   Approval pending.