| ELECTRICAL MACHINE |
| PAPER NO. 1 |
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| PUT ON: Dec, 2K2 |
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IC-203 ELECTRICAL MACHINE (B.Tech 3rd Semester, 2122) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1(a) Explain the following terms as applied to d.c. armature winding : (i) Pole Pitch (ii) Commutator Pitch. (b) In what type of d.c. machine lap winding is employed and why ? (c) Sketch the following types of d.c. generators : (i) Series (ii) Compound. (d) Write a short note on 'transformer cooling.' (e) What is advantage of V-V connections in transformer ? (f) Discuss briefly cogging. (g) What is meant by 'hunting' in a synchronous motor ? (h) List probable causes of failure of execitation of self-exited d.c. shunt generator. (i) Sketch shell type core construction of a 3-φ transformer. (j) Draw phasor diagram for a lagging power factor load of an auto-transformer. Section-B Marks:5 Each 2. Why is a commutator and brush arrangement necessary for operation of a d.c. machine ? 3. Distinguish between power and distribution transformer. 4. What is meant by equilent reactance of a transformer ? How may it be calculated in primary terms and secondary terms ? 5. What are the conditions for paralleling two 3-φ transformers? Differentiate between essential and desirable conditions. 6. Explain construction of a general purpose servomotor with the help of a diagram. Section-C Marks : 10 Each 7. A 4-pole, 50 Hz, 3-φ induction motor develops a maximum torque of 110 N-m at 1360 rpm. The resistance of the star-connected rotor is 0.25 ω/phase. Calculate the value of resistance that must be inserted in series with each rotor phase to produce a starting torque equal to half maximum torque. 8. Obtain the approximate equilent circuit of a given 200/2000 V, 1-φ, 30 kVA transformer having the following test results:
(a) Servo-motor (b) Repulsion motor (c) No-load test of speed control of induction motor |