problem 1: What do you mean by the term armature reaction? Describe the effect of armature reaction on the terminal voltage of an alternator at:
a) Unity power factor load
b) Zero loading P.F load
c) Zero lagging P-F load and draw the corresponding phasor diagrams.
problem 2: A 3-phase, star-connected, 1000 KVA, 2000v, 50Hz alternator gave the following open circuit and short-circuit test readings:
Field current: A 10 20 25 30 40 45
O.C voltage: V 800 1500 1760 2000 2350 2600
S.C armature current: A 200 250 300
Armature resistance per phase is 0.2?
problem 3: Draw the characteristics and find out the full load percentage regulation at:
a) 0.8 P.F. lead
b) 0.8 p.f lag.
problem 4: A 3-phase, 1500 kvA, star-connected, 50-Hz, 2300v alternator has a resistance of 0.12?. A field current of 70A produces short-circuit current equivalent to fuel load current of 376A in each line. The same field current produces an emf of 700V on open circuit. Find out the synchronous reactance of the machine and its full load regulation at 0.8 lagging power factor.
problem 5: Two three-phase alternators operate in parallel. The rating of one machine is 50MW and that of the other is 100MW. Both alternators are fitted with governors having a drop of 4%. How will the machines share a common load of 100MW?
problem 6: A synchronous generator operates on constant - voltage constant frequency bus bars. Describe the effect of variation of a) excitation b) steam supply on power output, power factor, armature current and load angle of the machine.
problem 7: Two station generators A and B operate in parallel station capacity of A is 50Mw and that of B is 25 Mw. Full load speed regulation of station A is 3% and full load speed regulation of B is 3.5%. Compute the load sharing if the connected load is 50MW, No-load frequency is 50Hz.
problem 8: What do you mean by the term synchronization of alternator? describe any one method of synchronizing?
problem 9: Describe the various methods for synchronization of alternators?