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

4. (a) define the method of calculating regulation and e?ciency of a 1- f trans-
former by open circuit and short circuit tests.
(b) A 200/400V, 50Hz, 1- f transformer has the subsequent test data
O.C. Test: 200V 0.7A 70 W -on L.V.Side
S.C Test: 15V 10A 85 W -on H.V.Side
compute the secondary voltage when delivering 5kW at 0.8lag. V1=200V.
[6+10]
5. (a) Prove that in a three phase induction motor
Starting torque
Maximum torque
= 2a
1+a2 Where a is the ratio of resistance to rotor stand still
reactance per phase.
(b) A 3300V, 24 poles, 50Hz 3phase star connected induction motor runs at
247 rpm, while supplying full load torque. Rotor resistance and stand still
reactance per phases are 0.016 and 0.265 ohms respectively. obtain out:
1 of 2Code No: 07A3EC13 Set No. 2
i. Speed at maximum torque and
ii. Ratio of full load torque to maximum torque. [8+8]
6. (a) elaborate the e?ects of harmonics on pitch and distribution factors?
(b) obtain the value of Kd for an alternator with nine slots per pole for the subsequent
cases:
i. 1 winding in all the slots
ii. 1 winding using only the ?rst 2/3 of the slots /pole
iii. 3 equal windings placed sequentially in 60o
group. [8+8]
7. (a) discuss the operation of single phase induction motor on the basis of :
i. double revolving ?eld theory
ii. Cross ?eld theory
(b) The subsequent test outcomes were found in case of 220V, 1-f induction motor
i. No load test: 220V, 5.8A, and 310watts
ii. Locked rotor test: 120V, 13.8A, 530watts
iii. Stator winding resistance is 1.4 ohms. Determine the approximate equiv-
alent circuit of the motor. [8+8]
8. (a) define the construction and working of PMMC instrument.
(b) Derive the formula for de?ection if the instrument is controlled.
(c) define the method of damping used in these instruments. [5+5+6]
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2 of 2Code No: 07A3EC13 Set No. 3
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

Earning:   Approval pending.