# Dr.A.P.J.Abdul Kalam University BE V SEM ALL BRANCH Electrical Machine- II [EX-502] Dec - 2020 Question Paper

Dr.A.P.J.Abdul Kalam University

Bachelor of Engineering

Fifth Semester Main Examination, December 2020

Electrical Machine- II [EX-502]

Branch-EX

Time: 3:00 Hrs Max Marks 70

Note : (i) Attempt any five questions out of eight.

(ii) All questions carry equal marks.

Q.1 (a) A 4-pole, wave-wound armature has 720 conductors and is rotated at1000 rev/min. If the

useful flux is 20 mWb, calculate the generated voltage.

(b) Explain Working Principles and e.m.f. equation of DC machine.

Q.2 (a) Explain armature reaction and methods of limiting armature reaction.

(b) Write Short Notes on – a) permanent magnet DC motors b) Brush less dc motors.

Q.3 (a) Why is starter necessary for D.C. motor? Explain different types of starter in D.C motor.

(b) Explain Different Methods of speed control of DC motors.

Q.4 (a) Explain Swinburne’s test and Hopkinson’s test of D.C. motor.

(b) Explain Operating characteristics of DC motors.

Q.5 (a) Explain Construction and Principle of operation of 3-Phase Synchronous Machine.

(b) What is Prime mover? Explain brushless excitation System.

Q.6 (a) Explain equivalent circuit of alternator and emf equation of3-Phase Synchronous Machine.

(b) Explain voltage regulation of alternators using synchronous impedance Method.

Q.7 (a) Discuss briefly the effect of varying excitation and mechanical torque of a synchronous motor.

(b) Why is Synchronous motor not self starting? What methods are generally used to start the

Synchronous motor?

Q.8 (a) What are the V-curves of a Synchronous motor? What are the main characteristics of a

Synchronous motor?

(b) Explain parallel operation and load sharing of an alternator.

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