3. Two generators (called A and B), each having no-load voltage of 500V, are connected in parallel to a constant load consuming 400 kW. The terminal potential drop of machine A falls linearly to 470 V as the load current is increased to 850 A while that of the other machine B falls linearly to 460 V when the load current is 600 A. (a) Draw the schematic diagram of the paralleled generators. (b) Determine the total loads current. (c) (i) Determine the terminal voltage of machine A, EA. (ii) Determine the terminal voltage of machine B, EB. (d) (i) Determine the current from generator A, IA. (ii) Determine the current from generator B, IB. (e) (i) Determine the power output from generator A, PA. (ii) Determine the power output from generator B, PB. (f) The induced emf of one machine is increased to share the load current equally. (i) Determine the new load current. (ii) Determine the terminal voltage of machine A, EA. (iii) Determine the terminal voltage of machine B, EB. (g) (i) Determine the current from generator A, IA. (ii) Determine the current from generator B, IB.
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- Draw two generators labeled A and B connected in parallel. - Connect the parallel combination to a load consuming 400 kW. Show more…
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Sri K.
A 480-V, 60-Hz, delta-connected, four-pole synchronous generator has the OCC shown in figure below. This generator has a synchronous reactance of 0.1 Ι and an armature resistance of 0.015 Ι. At full load, the machine supplies 1200 A at 0.8 PF lagging. Under full-load conditions, the friction and windage losses are 40 kW, and the core losses are 30 kW. Ignore any field circuit losses. a. How much field current must be supplied to the generator to make the terminal voltage 480 V at no load? b. If the generator is now connected to a load and the load draws 1200 A at 0.8 PF lagging, how much field current will be required to keep the terminal voltage equal to 480V? c. How much power is the generator now supplying? How much power is supplied to the generator by the prime mover? What is this machine's overall efficiency? d. If the generator's load were suddenly disconnected from the line, what would happen to its terminal voltage? e. Finally, suppose that the generator is connected to a load drawing 1200 A at 0.8 PF leading. How much field current would be required to keep Vt at 480 V?
Adi S.
8. The pulley of an old generator set has a diameter of 20 inches. The belt exerts a pull of 353 lbs on the pulley, and the generator set runs at 900 rpm. What is the approximate kW rating of the generator set? 9. A DC generator has a no-load output voltage rating of 120 V. The armature circuit resistance is 0.95 ohms, and its field coils are separately energized. If a load rated 2.2 kW at 115 V is connected across the terminals, neglecting the effect of armature reaction and line drop, what power would be absorbed by the load? 10. Two shunt generators A and B operate in parallel, and their load characteristic may be taken as a straight line. The voltage of generator A falls from 240 volts at no load to 220 volts at 200 amperes, while that of generator B falls from 245 volts at no load to 220 volts at 150 amperes. Determine the terminal voltage when the load is 67 kW.
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