Q4. What is the meant by "excitation" in an alternator? With the help of a neat diagram of brushless alternator labelling all the important parts. explain how the excitation is achieved in a brushless alternator.
Q5. A. (i) Sketch a diagrammatic arrangement of a static or self-excited alternator.; (ii) Describe the operation of the self-excited alternator; B. state why the voltage dip is less in the self-excited alternator than in brushless or conventional alternators.
Q10. A. What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance. (6)
B. Find the synchronous impedance reactance of an alternator in which a given field current produces an armature current of 200 A on short circuit and a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm. To what induced voltage must the alternator be excited if it is to deliver a load of 100A at a p.f of 0.8 lagging, with a terminal voltage of 200V. (10)
Q4. a) How is the Synchroscope connected for paralleling operation of alternator? (8)
b) Explain lamp bright method used to paralleling alternators. (8)
Q4. a) What is the purpose of AVR in an alternator? (6)
b) With the aid of a simple circuit diagram explain the basic working of a brushless alternator. (10)
Q8. a) List the parts of an alternator fitted with temperature alarms. (6)
b) Explain why heaters are fitted to an Alternator. (6)
c) Explain the function of an automatic voltage regulator. (4)
Q7. a) State the conditions, which must be satisfied before an A.C generator can be paralleled with live bus-bars. (4)
b) Sketch a lamp-bright configuration for synchronizing lamps. (8)
c) State the advantages and disadvantages of the lamps-bright system over lamps-darks system. (4)
Q5. (a) State the necessary conditions required prior to the synchronizing of electrical alternators. (6)
(b) Describe the type of cumulative damage that may be caused when alternators are incorrectly Synchronized. (6)
(c) Explain how the damage referred to in (b) can be avoided/reduced. (4)
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