Code No: RR220402
Set No. 1
II B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007
ELECTRICAL TECHNOLOGY
( Common to Electronics & Communication Engineering, Computer Science
& Engineering, Information Technology, Computer Science & Systems
Engineering, Electronics & Telematics, Electronics & Computer Engineering
and Instrumentation & Control Engineering)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
⋆ ⋆ ⋆ ⋆ ⋆
1.
(a) Draw and explain typical no-load & load characteristics of a D.C. Series Gen-
erator.
(b) A shunt generator has following magnetizing curve:
If(amps) 0 0.5 1.0 1.5
2.0
E(Volts)
4
42
78
93
100
Calculate the value of critical field resistance. Also find the value of open-
circuit voltage when field resistance is 60 ohms.
[8+8]
2.
(a) Explain speed control of a D.C Series Motor.
(b) A 200 V d.c. Series Motor runs at 1000rpm when operating at its full load
current of 30 A. The motor resistance is 0.5Ω and the magnetic circuit can be
assumed unsaturated what will be the speed if
i. the load torque is increased by 44%
ii. the motor current is 20 A.
[6+10]
3.
(a) Explain the principle of operation of transformer. Derive its e. m. f. equation.
(b) A 1-phase transformer has 180 turns respectively in its secondary and primary
windings. The respective resistances are 0.233Ω and 0.067Ω.
Calculate the equivalent resistance of
i. the primary in terms of the secondary winding,
ii. the secondary in terms of the primary winding, and
iii. the total resistance of the transformer in terms of the primary.
[8+8]
4.
(a) What are the transformer tests? Explain.
(b) Calculate the efficiencies at half-full and 11/4 load of a 100kVA transformer for
power factors of
i. unity;
ii. 0.8, the copper loss is 1000W at full load = iron loss.
[10+6]
5.
(a) Explain the rotor resistance starter for an induction motor.
1 of 2
Code No: RR220402
Set No. 1
(b) A 3-phase, 6 pole, 400 V, 50 Hz induction motor. takes a power input of 35
kW at its full-load speed of 890 r.p.m. The total stator loss