Question

In: Electrical Engineering

480 V, 200 kVA, 08 PF lagging, 60 Hz two pole Y connected synchronous generator has...

480 V, 200 kVA, 08 PF lagging, 60 Hz two pole Y connected synchronous generator has a synchronous reactance of 0.25 Ω and an armature resistance of 0.03 Ω. At 60 Hz, its friction and windage losses are 6 kW, and its core losses are 4 kW. The field circuit has a dc voltage of 200 V, and the maximum IF is 10 A. The resistance of the field circuit is adjustable over the range from 20 to 200 Ω. The OCC of the generator is shown in figure

a. How much the field current is required to make VT equal to 480 V when the generator is running at no load? [4.55 A]

b. What the internal generated voltage of this machine at rated conditions? [322 @ 7.8°]

c. How much the field current is required to make VT equal to 480 V when the generator is running at rated conditions? [558 V]

d. How much power and torque must the generator’s prime mover be capable of supplying? [175.2 kW, 465 Nm]

e. Assume that the field current of the generator is adjusted to achieve rated voltage (480 V) at full load conditions in each of the questions below.

1. What is the efficiency of the generator at rated load? [91.3%]

2. What is the voltage regulation of the generator if it is loaded to rated kilovoltamperes with 0.8-PF lagging loads? [16.2%]

3. What is the voltage regulation of the generator if it is loaded to rated kilovoltamperes with 0.8-PF leading loads? [-9.0%]

4. What is the voltage regulation of the generator if it is loaded to rated kilovoltamperes with unity power-factor loads? [5.1%]

f. Assume that the field current of the generator in Problem 5-2 has been adjusted so that it supplies rated voltage when loaded with rated current at unity power factor. (You may ignore the effects of RA when answering these questions.)

1. What is the torque angle δ of the generator when supplying rated current at unity power factor? [12°]

2. What is the maximum power that this generator can deliver to a unity power factor load when the field current is adjusted to the current value? [941 kW]

3. When this generator is running at full load with unity power factor, how close is it to the static stability limit of the machine? [196 kW]

4. Plot the torque angle δ as a function of the power supplied by the generator for these conditions.

3. A 3-phase 50-Hz star-connected 2000-kVA, 2300 V

Expert Solution

Manojponduru answered 1 year ago

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