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Q3: (a) Determine the terminal voltage of a dc shunt generator which develops an e.m.f. of...

Q3: (a) Determine the terminal voltage of a dc shunt generator which develops an e.m.f. of 240V and has an armature current of 50 A on load. Assume the armature resistance is 0.04Ω. [3 marks]

(b) A lap wound armature is used in a 4-pole dc machine and 70 coils on the armature each containing 10 turns. The flux per pole in the machine is 40 mWb and the machine rotates at 500 rpm; (a) How many current paths are there in the machine, (b) What is its induced voltage (c) Find the emf per turn of the coil. [3 marks]

(c) (i)Draw the speed vs load curve of a dc shunt motor and a dc series motor [1 mark]

(ii) Draw torque vs load curve of a dc separately excited motor. [1 marks]

(iii) Why the demagnetization in a dc motor is more dangerous when compared to a dc generator? Note that the demagnetization occurs due to the armature reaction in a dc machine.

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