GTU Electrical Machine - January 2014 Exam Question Paper

GTU Electronics and Communication Engineering (Semester 3)
Electrical Machine
January 2014

Total marks: --
Total time: --

INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Discuss open delta connections of transformers with necessary circuit and vector diagrams.

7 M

1 (b) What do mean of an ideal transformer and derive emf equation of a single phase transformer. Also define Transformation Ratio.

7 M

2 (a) Derive the condition for Maximum torque for induction motor and Explain Torque - Slip characteristics.

7 M

2 (b) Obtain the equivalent circuit of a 200/400V, 50 Hz, 1 Phase
Transformer from the following test data
O.C.Test : 200 V,0.7 A,70 W - on L.V. side
S.C. Test : 15 V, 10 A, 85 W - on H.V. side
Calculate the secondary voltage when delivering 5 KW at 0.8 p.f.
lagging , the primary voltage being 200V.

7 M

2 (c) Write and explain the conditions of parallel operation of 3-phase transformer.

7 M

3 (a) Explain the phenomena of armature reaction of a DC machine. State its Remedies.

7 M

3 (b) What is commutation? Give remedies for commutation.

7 M

3 (c) Draw and explain the internal and external characteristics of d.c. shunt generators.

7 M

3 (d) Explain different parts of DC machine with neat and clean diagram.

7 M

4 (a) Explain different speed control methods for 3 phase induction motor.

7 M

4 (b) Explain the procedure to construct the circle diagram for induction motor & how various quantities are measured from circle diagram.

7 M

4 (c) Explain different methods for speed control of series motors.

7 M

4 (d) Write different starters used for 3 phase induction motor and explain any one of them.

7 M

5 (a) Define and state the expressions for (i) Pitch factor. (ii) Distribution factor for Alternator.

7 M

5 (b) What is voltage regulation? How it can be determined by using Zero power factor method in synchronous machine?

7 M

5 (c) State the different methods of finding voltage regulation in alternator. Explain any one of them in detail.

7 M

5 (d) State and explain condition of synchronizing alternator with infinite bus bar.

7 M

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