2ND 9 Flashcards
An AC armature is always the:
a) rotating part of the generator
b) stationary part of the generator
c) conductors into which voltage is induced
d) conductors through which DC exciter current flows
c) conductors into which voltage is induced
The AC field is always the:
a) rotating part of the generator
b) stationary part of the generator
c) conductors into which voltage is induced
d) conductors through which DC exciter current flows
d) conductors through which DC exciter current flows
The output of a revolving field type AC generator is taken from:
a) sliprings and brushes
b) commutator bars and brushes
c) fixed terminals
d) none of the above
c) fixed terminals
The revolving field type AC generator is most widely used because:
a) the stator can be connected to the external circuit without the use of moving contacts
b) only two sliprings are required to carry the relatively small low-voltage field current
c) of improved safety features
d) all of the above
d) all of the above
The armature windings of a 3-phase AC generator are physically placed so that the induced voltages are out of phase by:
a) 120 degrees
b) 90 degrees
c) 60 degrees
d) 30 degrees
a) 120 degrees
The output frequency of an AC generator is dependent upon the:
a) number of poles and phases
b) number of poles and rotor speed
c) rotor speed and phases
d) all of the above
b) number of poles and rotor speed
The field-pole windings on AC generators are connected in:
a) series
b) parallel
c) series-parallel
d) series only for salient pole machines
a) series
The load rating of an AC generator is determined by the:
a) overload it can carry for a specified time only
b) load it is capable of supplying
c) load it can carry continually
d) internal heat it can withstand
d) internal heat it can withstand
The voltage output of an AC generator is controlled by:
a) regulating the speed of the prime mover
b) varying the DC exciter voltage
c) varying the reluctance of the air gap
d) shorting out part of the armature windings
b) varying the DC exciter voltage
All of the below statements apply to a wye-connected AC generator except:
a) the phase winding voltage is equal to the phase-to phase voltage
b) the voltage values per armature coil are lower than those of delta-connected generator
c) the connection provides a common neutral point for grounding
d) the connection provides a common neutral point for relay protection
a) the phase winding voltage is equal to the phase-to phase voltage
Armature reaction is most nearly associated with the effects of:
a) rotor speed
b) armature flux
c) distorted flux lines
d) none of the above
b) armature flux
The terminal voltage of an AC generator is affected by:
a) armature resistance
b) armature reactance
c) the effect of armature reaction
d) all three of the above factors
d) all three of the above factors
The terminal voltage of an AC generator will change with a change in load characteristics. The below statements apply to this principle and are all true except for:
a) the greater the load the greater will be the drop or rise in terminal voltage
b) the terminal voltage will tend to drop with a leading power factor
c) the lower the lagging power factor the greater will be the voltage drop
d) the lower the leading power factor the greater will be the voltage rise
b) the terminal voltage will tend to drop with a leading power factor
Before connecting two or more three-phase AC generators in parallel it is necessary that:
a) the effective voltage of the incoming generator be equal to the bus-bar voltage
b) the frequency of the incoming generator must be equal to that of the bus-bars
c) the phase voltages must be in proper relation and the phase sequence of the three phases of the incoming generator must be the same as that of the bus-bars
d) all three of the above
d) all three of the above
The voltage of an AC generator rises from 4600 volts at full load to 5350 volts at no load. The percent regulation is approximately:
a) 14
b) 16
c) 18
d) 20
b) 16
