Synchronous Generator Objectives Part 03

41 . An alternator has full load regulation of 4% when the power factor of the load is 0.8 lagging while alternator runs at 1500 rpm. The full load regulation of 1400 rpm for 0.8 pf lagging load will be 4 percent

42 . The Potier’s triangle separates the armature leakage reactance and armature reaction mmf.

43 . In the Potier’s triangle, the Potier’s reactance drop per phase is 22 volts per phase at 88 amperes per phase. The Potier’s reactance per phase is 0.25

44 . Two alternators are running in parallel. The excitation of one of the alternator is increased. The result will be wattless component will change.

45 . The power output of an alternators is 100 kW. In order that the tangent of pf angle may be 0.8 lagging, the KVAR rating must be -80 KVAR.

46 . The power output of an alternator is 40 kW and KVAR component is – 25. What will be the value of tanφ (φ being the power factor angle) ? 0.625 leading

47 . When short pitch coils of 160 are used in an alternator, which harmonic component will not be present in the output emf? ninth.

48 . A 120 MW turbo alternator is supplying power to 80 MW load at p.f. lagging. Suddenly the steam supply to the turbine is cut off and the alternator remains connected to the supply network and the field supply also remains on. What will happen to the alternator? The alternator will continue to run as a synchronous motor rotating in the same direction

49 . The figure shows the characteristics of an alternator. Which curve represents synchronous impedance? curve A

50 . In the above figure (Figure of Question 49) which curve represents short circuit? curve C

51 . In the above figure which curve represents open circuit voltage? curve D.

52 . For a peripheral speed of 314 m/s, a 2 pole cylindrical machine will have maximum diameter of 200 cm

53 . The rotor of the salient pole alternator has 24 poles. The number of cycles of emf in one revolution would be 12

54 . Two alternators A and B are sharing an inductive load equally. If the excitation of alternator A is increased alternator B will deliver less current and alternator A will deliver more current

55 . Desirable feature for the parallel operation of two alternators is both should have less of resistance as compared to synchronous reactance

56 . Alternators used in aircraft systems usually have frequency of 400 Hz.

57 . High frequency on aircraft alternators is selected in order to reduce the bulk.

58 . A 20 pole ac generator rotates at 600 rpm. The periodic time of current in seconds per cycle is 0.01

59 . What kind of rotor is most suitable for turbo alternators? non-salient pole type

60 . The synchronizing power developed in one of the alternators, when two alternators are running in parallel, will load the same alternator in which it is developed and reduce its speed (A) True