9 - 21 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 excitor current flows
C) Conductors into which voltage is induced
page 1 & 3
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 excitor current flows
D) Conductors through which DC exciter current flows
page 3
The output of a revolving field type AC generator is taken from:
A) Slip rings 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 with out use of moving contact
B) Only two slip rings 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
page 1
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
page 6
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
page 1 & 3
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
page 3
The load rating of an AC generator is determined by the:
A) Over load it can carry for a specified time only
B) Load it is capable of supplying
) Load it can carry continually
D) Internal heat it can withstand
D) Internal heat it can withstand
page 13
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 winding
B) Varying the DC exciter voltage
page 13
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 generators
C) The connection provides a common neutral point for gronding
D) The connection provides a common neutral point for a relay protection
A) The phase winding voltage is equal to the phase to phase voltage (this is a Delta connection)
page 6
Armature reaction is most nearly associated with the effects of:
A) Rotor speed
B) Armature flux
C) Distorted flux bres
D) None of the above
B) Armature flux
page 9
The terminal voltage of an AC generator is affected by
A) armature resistance
B) armature reaction
C) armature reactance
D) All 3 of the above factors
D) All 3 of the above factors
page 9
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 drops 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 lagging power factor the greater will be the voltage rise
B) The terminal voltage will tend to drop with a leading power factor
Before connection 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 3 of the above
D) All 3 of the above
page 11
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
R=(no load - full load) / full load x 100
R=(5350-4600)/4600 x 100
R=750/4600 x 100
R=0.1630 x 100
R= 16.3%
page 11
