Download GTU BE/B.Tech 2018 Winter 4th Sem New 2140906 Ac Machines Question Paper

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Subject Code: 2140906

GUJARAT TECHNOLOGICAL UNIVERSITY

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Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

1. (a) Explain working principle of Induction Generator. [03]
   

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   (b) Derive the EMF equation of an alternator. [04]
   (c) Mention different starters for three phase induction motor and explain Auto-transformer starter in details. [07]
2. (a) Compare squirrel cage and slip ring Induction Motor. [03]
   (b) Write a short note on auto synchronous motor. [04]
   (c) Explain the phenomena of crawling and cogging in induction motor. [07]
   

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   OR
   (c) Explain the procedure to construct the circle diagram of induction motor. Also describe the method to determine losses, efficiency and slip at full load condition using circle diagram. [07]
3. (a) Derive the torque equation for 3phase Induction Motor. [03]
   (b) List out the methods of speed control of Induction Motor. [04]
   (c) Explain any one in detail. [07]

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4. (a) Define and describe the effect of Armature reaction in an alternator. [03]
   OR
   (a) Explain with reason why synchronous motor is not self starting. [03]
   (b) Discuss the methods of starting of synchronous motor. [04]
   (c) Explain V-curves and its importance for synchronous motor. [07]

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5. (a) Explain the determination of direct axis and quadrature axis synchronous reactance using slip test. [03]
   (b) Explain the construction and working of universal motor. [04]
   (c) List the methods of determination of voltage regulation of an alternator. Explain any one in detail. [07]
   OR
   (c) State the conditions to be satisfied for putting a 3 phase alternator in parallel with infinite bus. [07]

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6. (a) Briefly describe the construction and working of linear induction motor. [03]
   (b) Explain any one method for starting of 3phase squirrel cage induction motor. [04]
   (c) Define the pitch factor and distribution factor in case of synchronous motor. [07]
7. (a) Derive the condition for maximum starting torque for three phase induction motor. [03]
   (b) Discuss the procedure to perform no load and blocked rotor tests on a three phase induction motor. [04]
   

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   (c) What is hunting? How to minimize it? [03]
8. (b) What is synchronization? Explain two bright one dark lamp method of Synchronization. [04]
   (c) What is the role of commutator in A.C. commutator motor? Explain working of Schrage Motor. [07]

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