51. Power factor of an alternator driven by constant prime mover input can be changed by changing its
- speed
- load
- field excitation
- phase sequence
52. How can the reactive power delivered by a synchronous generator be controlled?
- by changing the prime mover input
- by changing the excitation
- by changing the direction of rotation
- by changing the prime mover speed
53. The rating of the prime mover driving an alternator is determined entirely by its _____ rating.
- voltage
- current
- kW output
- speed
54. The rating of a synchronous machine is usually governed by its
- speed
- temperature rise
- weight
- none of these
55. The flux set up by the armature current, which does not cross the air gap an takes a different path is called the _____ flux.
- leakage
- main
- cross-magnetizing
- demagnetizing
56. The magnitude of the leakage flux depends on
- the magnitude of armature current
- phase angle between armature current and terminal voltage
- air gap thickness
- both (1) and (2)
57. Armature reaction effect is/are _______ on the main field flux.
- cross-magnetizing as well as demagnetizing
- only demagnetizing
- only cross-magnetizing
- only magnetizing
58. The armature reaction effect in a synchronous machine depends on
- load current
- power factor of the load
- speed of the machine
- both (1) and (2)
59. In a synchronous generator, the effect of cross-magnetization is to make the generated voltage
- truly sinusoidal
- non-sinusoidal
- free from harmonics
- none of these
60. In an alternator, the armature mmf will be in phase with the main field flux only when the load is purely
- resistive
- inductive
- capacitive
- both inductive and capacitive