Q4. a) Explain the significance of the root-mean-square value of an alternating current or voltage waveform. Define the form factor of such a waveform. (6)
b) A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the KVA rating of the other alternator and the power factor. (10)
Q5. A) By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vm Sinwt, what is the voltage across the load resistor? (6)
b) A battery-charging circuit is shown below in fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1.0 A. (10)
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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