2-1-15
Generators with small kilovolt-ampere ratings are usually ? cooled. Select one: a.air b.halon c.hydrogen d.nitrogen
A. Air
Another name for an AC generator is the ? . Select one: a.alternator b.converter c.dynamo d.phasor
A. Alternator
Brushes and slip rings limit the amount of power that can be generated with the revolving ? type of generator. Select one: a.armature b.field c.shunt d.stator
A. Armature
The two basic types of alternators are the revolving armature type and the revolving ? type. Select one: a.field b.rotor c.shunt d.stator
A. Field
A generator has four poles and a speed of 1,500 rpm. What is the output frequency? Select one: a.33 Hz b.50 Hz c.67 Hz d.100 Hz
B. 50 Hz
The ? rotor uses a longer and narrower construction to minimize wind resistance and centrifugal forces. Select one: a.concentric b.round c.salient pole d.stretched
B. Round
Two types of rotating field construction are the salient pole rotor and the ? rotor. Select one: a.concentric b.round c.series d.solid
B. Round
How many poles are required for a generator to have a frequency of 60 hertz at 1,200 rpm? Select one: a.3 b.5 c.6 d.9
C. 6
To generate a frequency of 50 hertz with an eight-pole generator, the speed of rotation must be ? . Select one: a.375 rpm b.563 rpm c.750 rpm d.1,125 rpm
C. 750 rpm
Large capacity alternators are often enclosed in a ? atmosphere for cooling purposes. Select one: a.freon b.halon c.hydrogen d.nitrogen
C. Hydrogen
Both AC and DC generators operate on the principle of electromagnetic ? . Select one: a.conduction b.coupling c.induction d.transfer
C. Induction
The output voltage of an alternator is controlled by increasing or decreasing the strength of the ? field. Select one: a.armature b.force c.magnetic d.stator
C. Magnetic
A generator is a device that converts ? energy into electrical energy. Select one: a.kinetic b.magnetic c.mechanical d.potential
C. Mechanical
When using the "three lamp" method, the two alternators are in phase with each other when all of the lamps are ? . Select one: a.blinking at the same time b.blinking in sequence c.off d.on
C. Off
An AC generator uses ? to directly connect the armature windings to the load. Select one: a.brushes b.commutators c.slip rings d.transformers
C. Slip rings
The ? is the rotating portion of an AC generator or motor. Select one: a.commutator b.core c.revolver d.rotor
D. Rotor
When the armature is held stationary in a generator, it is called the ? . Select one: a.core b.pole c.stabilizer d.stator
D. Stator
One method of detecting when the direction of the magnetic field or phase rotation of one alternator is matched with that of a paralleled alternator is to use ? . Select one: a.a frequency meter b.a phase meter c.an oscilloscope d.three lamps
D. Three lamps
The factors that determine the frequency of an alternator are the number of slip rings and the speed of rotation of the rotor. Select one: True False
False
The three factors that determine the output voltage of an alternator are the diameter of the slip rings, the strength of the magnetic field, and the speed of rotation of the conductor in the magnetic field. Select one: True False
False
Pole faces that jut out and are very pronounced are called ? poles. Select one: a.dominant b.parallel c.projecting d.salient
Salient
Higher voltages and kilovolt-ampere ratings can be obtained in commercial generators by using a revolving field and a stationary armature. Select one: True False
True
Slip rings, unlike a commutator, are constructed as a continuous ring with each end of the armature loop connected to a separate ring. Select one: True False
True
When connecting two, 3-phase alternators in parallel, the output voltages of the two machines must be equal. Select one: True False
True
What is the mathematical formula for determining the frequency of an alternator? Select one: a.F = (S × P) ÷ 60 b.F = (S × P) ÷ 90 c.F = (S × P) ÷ 120 d.F = (S × P) ÷ 180
c.F = (S × P) ÷ 120
In a 3-phase generator, the three sets of windings are placed ? apart. Select one: a.30° b.60° c.90° d.120°
d.120°
