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Q3. A. Sketch a standby battery charging/discharging circuit;

B. Describe the circuit sketched, making special reference to how battery charge is maintained and how it operates upon loss of main power.

Q3. A. Explain why it is necessary to have reverse power protection for alternators intended for operation.

B.(i) Sketch a reverse power trip; (ii) Explain briefly the principle on which the operation of this power trip is based and how tripping is activated.

Q2. A. (i) Describe with the aid of a sketch the operation of a synchro scope; (ii) State the information obtained from it. B. Suggest a substitute in the event of synchro scope and stand by light failure.

Q3. List at least two factors that cause deterioration of the frequency response of a transistor amplifier. Explain how each factor affects the performance of the amplifier and the portion of the frequency range where it is effective. (16)

Q4. Differentiate with the aid of simple sketches between two of the following types of electronic circuits.

A. Rectifier circuit (6)

B. Amplifier circuit (5)

C. Oscillator circuit (5)

Q8. A. What is meant by negative and positive feed backs? Explain the characteristics of negative feedback; B. Compare the series and parallel resonance circuits. Find the frequency at which the following circuit resonates.

Q7. A. Describe the no-load saturation characteristic of a d.c. generator.

B. A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 . The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate;

(i) The speed;

(ii) The gross torque developed by the armature.

Q8. A. What is slip? What are the factors on which the torque or an induction motor depends?  B) Calculate the pitch factors Kp for a wiping having 24 stator slots, 4 poles, when the coil span is 1 to 6

Q10. A. How does change to frequency affect the operation of the transformer? What makes this ratio different from the ratio of transformer? B. A 550 KVA, 50 Hz single phase transformer has 1875 and 75 turns in the primary and secondary windings respectively. If the secondary voltage is 220 V, calculate (i)Primary voltage; (ii)Primary and secondary currents; iii. Maximum value of flux.

Q7. A. Which of the following three motors has the poorest speed regulation: shunt motor, series Motor or cumulative compound motor? Explain.

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.