Q4. a) What are the characteristics of PN junction diode? Point out its specifications. Also point out the significance of dynamic and static resistances. (6)
b) Draw the circuit of half-wave rectifier and its output waveform. A diode whose internal resistance is 20 Ω is to supply power of 1000 Ω load from 110 V (RMS) source. Calculate
(a) Peak load current
(b) DC load current
(c) AC load current. (10)
Q5. a) Describe the no-load saturation characteristics of a D.C. generator. (6)
b) A D.C. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 Ω. The machine has six poles and the armature is lap- connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate (10)
i) The speed
ii) The gross torque developed by the armature.
Q6. A) What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance. (6)
b) A three-phase induction motor is wound for four poles and is supplied from a 50 HZ system.
Calculate:
(i) The synchronous speed
(ii) The speed of the rotor when the slip is 4 percent
(iii) The rotor frequency when the speed of the rotor is 600 r/min. (10)
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