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Q10. A. Write shorts notes on various types of DC Motors.

B. A 440V shunt motor takes an armature current of 30A at 700 rev/min. The armature resistance is 0.7ohm. If the flux is suddenly reduced by 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged resisting torque to motion, what will be the new steady values of speed and armature current? Sketch graphs showing armature current and speed as functions of time during the transition from initial to final, steady-state conditions.

Q4. With reference to preferential tripping in a marine electrical distribution system.

A. With the aid of a sketch, describe a typical arrangement to provide three stages of tripping an instantaneous protection against short circuit.

B. State why this protection is required;