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Q3. Which of the following devices will prevent a DC generator from becoming motorized?

a) Over current relay

b) Motorization trip

c) Reverse power relay

d) Reverse current relay.

why the remaining options were not considered. (16)

Q5. (a) Describe the no-load saturation characteristic of a d.c. generator. (6)

(b) A 400V shunt motor has an armature resistance of 0.3 ohm and a shunt-field circuit resistance of 300 ohm. Calculate the speed attained by the motor when the current taken from the supply is (i) 30A and (ii) 50A. The open-circuit characteristic of the machine, when driven as a generator at 1500 rev/min, is given by the following figures:

Neglect the effects of armature reaction (10)

Q1. (a) Draw a 4-pole D.C. generator construction diagram labelling its main parts. (8)

(b) Describe briefly its (8)

(i) Field system

(ii) Armature

(iii) Commutator

(iv) Brushes