Q6. (a) Sketch an arrangement showing the principal of a proportional plus Integral (P + I) control loop. (6)
(b) Compare the series and parallel resonance circuits. Find the frequency at which the following circuit resonates. (10)
Q4. A) Explain the potential hazards if liquid-cooled transformers are used. (6) b) What are the losses in transformers? Mention the various factors which affect these losses. In a 25 KVA, 3300/233 V, single phase transformer, the iron and full-load Cu. Losses are respectively 350 and 400 w. Calculate the efficiency at half-full load 0.8 power factor. (10)
Q6. a) Compare the effectiveness of a current limiting circuit breaker with that of a HRC fuse.
b) A 440 V shunt motor takes an armature current of 30 A at 700 rev/min. The armature resistance is 0.7 ohm. If the flux is suddenly reduced 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged 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. (10)
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