RR220402 Electrical Technology B.Tech Question Paper : djriet.edu.in

Name of the College : Dasari Jhansi Rani Institute Of Engineering And Technology
University : JNTUK
Department : Computer Science And Engineering
Subject Code/Name : RR220402 – Electrical Technology
Year : 2008
Degree : B.Tech
Year/Sem : II/II
Website : djriet.edu.in
Document Type : Model Question Paper

Electrical Technology II Year II Sem Supple Apr/May 2008  : https://www.pdfquestion.in/uploads/djriet.edu.in/2973-RR220402-ELECTRICAL-TECHNOLOGY.pdf
Electrical Technology II Year Supple Aug/Sep 2008 : https://www.pdfquestion.in/uploads/djriet.edu.in/2973–RR220402-ELECTRICAL-TECHNOLOGY.pdf

DJRIET Electrical Technology Question Paper

II B.Tech II Semester Supplimentary Examinations, Apr/May 2008 :
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)

Related : Dasari Jhansi Rani Institute Of Engineering And Technology R05320401 Telecommunication Switching Systems And Networks B.Tech Question Paper : www.pdfquestion.in/3027.html

Time: 3 hours
Max Marks: 80
Answer any FIVE Questions :

Set – I

All Questions carry equal marks :
1. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator?
(b) What is the main purpose of laminating the armature core of a D.C. Generator.
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03 , series field resistance is 0.04 and shunt field resistance is 200 . The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8]

2. (a) What is the significance of the back e.m.f. of a D.C. Motor?
(b) Deduce the condition for maximum power for a D.C. Motor?
(c) A 220V shunt motor with an armature resistance of 0.5 is excited to give constant main field. At full load the motor runs at 500 rpm and takes an armature current of 30A. If a resistance of 1.0 is placed in the armature circuit, find the speed at
i. full-load torque
ii. double full-load torque. [4+4+8]

3. (a) Explain the principle of operation of a single-phase transformer when it supplies lagging power factor load. Draw the phasor diagram under this condition.
(b) A 4 kVA, 200 / 400 V, 50 Hz, transformer gave the following the test figures:
No Load: Low voltage data: 200 V 0.7 A 60 W
Short Circuit: High voltage data: 9 V 6A 21.6 W
Calculate the magnetizing current and component corresponding to iron loss at normal voltage and frequency. Find the efficiency on full load at unity power factor. Also determine the regulation at half-full load 0.707 leading power factor. [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 various power stages of a 3-phase induction motor.
(b) A 3-phase induction motor with r2 / x2 = 0.5, has a starting torque of 25.0 Nm. For negligible stator impedance and no-load current, determine the starting torque in case the rotor-circuit resistance per phase is
i. doubled
ii. halved. [6+10]
6. (a) Derive e.m.f equation for an alternator and explain distribution factor and pitch factor used in e.m.f. Equation.
(b) Write the expression showing the relationship between speed frequency and no. of poles of a synchronous machine. The speed of rotation of the turbine driving an alternator is 166.7 r.p.m. What should be the no. of poles of the alternator if it is to generate voltage 50HZ. [10+6]
7. (a) Explain the principle of operation of synchronous motors.
(b) A 3-phase alternator is rated at 5 KVA, 110V, 26.3A, 50 Hz and 1200 r.p.m. The stator resistance between terminals as measured with dc is 0.2 ohm. With no load and rated speed the stator line voltage is 160V for a field current of 4A.At rated speed, the short circuit stator current per terminal is 50A for a field current of 4A.compute voltage regulation of alternator at 0.8 p.f. Lagging. Using synchronous impedance method. [8+8]
8. (a) Draw a diagram showing the construction of a stepper motor and discuss its operation.
(b) Discuss the various applications of stepper motor. [10+6]

Set – II

1. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator?
(b) What is the main purpose of laminating the armature core of a D.C. Generator.
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03 , series field resistance is 0.04 and shunt field resistance is 200 . The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8]
2. (a) From the first principles, derive an equation for torque developed in a D.C. Motor.
(b) A 20kw, 250V d.c. shunt generator has armature and field resistances of 0.04 and 200 respectively. Determine the total armature power developed when working.
i. as generator delivering 20kw output and
ii. as a motor taking 20kw input. [8+8]
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 0.233 and 0.067 .
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. Write short notes on:
(a) OC and SC tests on transformers.
(b) Losses in transformers. [10+6]
5. (a) Sketch torque-speed characteristics of an induction motor working at rated voltage and frequency, deriving necessary expressions.
(b) A 3-phase, 50 Hz, 400 V, wound-rotor induction motor runs at 960 r.p.m. at full-load. The rotor resistance and standstill reactance per phase are 0.2 and 1 respectively. If a resistance of 1.8 is added to each phase of the rotor at standstill, what would be the ratio of starting torque with full voltage and the added resistance to the full-load torque under normal running conditions? [8+8]
6. (a) Define voltage regulation of an alternator. Explain synchronous impedance method of determining regulation of an alternator.
(b) Calculate the voltage induced per phase in a 3phase 50 Hz, alternator having a flux per pole of 0.1515 wb. The no. of conductors in series are 360. Assume full pitch coil with a distribution factor of 0.96. [8+8]
7. (a) Explain why a synchronous motor doesn’t have self-starting torque. Explain one method of starting a synchronous motor.
(b) A 3phase, 3300v, star connected synchronous motor has a synchronous re actance of 5ohm per phase. The input to the motor is 1000kw at a normalvoltage and the induced line e.m.f is 4000v.Calculate the line current. Neglect armature resistance. [8+8]
8. (a) Give the description of A.C tachometer and mention its applications.
(b) Write a short note on shaded pole type servo-motor. [8+8]