What will happen if the input power from the prime mover is kept the same but the excitation of the alternator is changed?
AThe active component of the output is changed
BThe reactive component of the output is changed
CThe power factor of the load will change from lagging to leading
DThe power factor of the load will change from lagging to unity
#142📘 EE Pocket Reviewer RojasEasy
A rotating field type alternator receives its excitation voltage from which of the following?
AFrom an external ac voltage source
BFrom another alternator
CFrom a self-excited source like a dc generator
DFrom an auxiliary generator driven by the main generator shaft
#143📘 EE Pocket Reviewer RojasEasy
If the input of the alternator is kept constant but its excitation is changed, then which of the following will remain the same?
AkVAR output
BkVA output
CkW output
DOperating pf
#144📘 EE Pocket Reviewer RojasEasy
The magnitude of the three-phase voltage drops in an alternator due to armature resistance, leakage reactance and armature reaction is solely determined by which of the following?
AArmature current
BPower factor of the load
CField construction of the alternator
DAll of these
#145📘 EE Pocket Reviewer RojasEasy
When an alternator is supplying a unity pf load, the armature reaction will produce which of the following conditions?
ADemagnetization of the main field flux
BCross magnetization of the main field flux
CMagnetization of the main field flux
DAll of these
#146📘 EE Pocket Reviewer RojasEasy
What is the reason why three-phase alternators are normally Y-connected?
AThe terminal voltage is higher
BThe magnetic losses are reduced
CThe number of turns of wire are lesser
DThe size of conductors are smaller
#147📘 EE Pocket Reviewer RojasEasy
Which of the following defines the voltage regulation of an alternator?
AIt is the reduction in the terminal voltage when the alternator is being loaded
BIt is the increase in the terminal voltage when loaded from lagging pf to leading pf
CIt is the increase in the terminal voltage when load is switched off from the alternator
DIt is the variation in the terminal voltage in respect to the excitation of the alternator
#148📘 EE Pocket Reviewer RojasEasy
What is the advantage of using a short pitch windings on alternators?
AReduced eddy currents
BSuppression of harmonics.
CHigher voltage generated.
DLesser noise
#149📘 EE Pocket Reviewer RojasEasy
An alternator is delivering power at a particular frequency. Which of the following can increase the operating frequency?
AIncrease the excitation
BDecrease the excitation
CIncrease the armature speed
DDecrease the armature speed
#150📘 EE Pocket Reviewer RojasEasy
Which statement is true about a salient pole type rotor in comparison to a cylindrical pole type rotor?
AIt is smaller in diameter and larger in axial length
BIt is larger in diameter and smaller in axial length
CIt is larger in diameter as well as axial length
DIt is smaller in diameter as well as axial length
#151📘 EE Pocket Reviewer RojasEasy
What is the disadvantage of using a short pitched coil in an alternator?
AThe voltage around the coil is reduced
BIt will produce harmonics
CIt increases the copper losses at the end connection
DIt causes unbalanced to the three-phase
#152📘 EE Pocket Reviewer RojasEasy
Which of the following is the effect of overheating of the alternator’s windings?
AIt reduces the voltage generated
BIt reduces the life of the machine
CIt reduces the operating power factor
DIt doesn't have any significant effect
#153📘 EE Pocket Reviewer RojasEasy
High speed alternators are driven by which of the following types of prime movers?
ASteam turbines
BHydraulic turbines
CDiesel engines
DAny of these
#154📘 EE Pocket Reviewer RojasEasy
The field windings of an alternator is excited with what current?
AAC only
BDC only
CEither AC or DC
DAny type of current
#155📘 EE Pocket Reviewer RojasEasy
If the input of the alternator is kept constant but its excitation is increased, then which of the following will happen?
AIts kVA will be leading
BIts kVA will be lagging
CIts kW will increase and its kVAR the same
DIts kW will decrease and its kVAR will increase
#156📘 EE Pocket Reviewer RojasEasy
What is the advantage of using salient poles in an alternator?
ALosses are reduced
BBearing loads are reduced
CIt is applicable to both low and medium speed prime movers
DFriction and windage loss will be reduced
#157📘 EE Pocket Reviewer RojasEasy
Two alternators are connected in parallel. Their kVAR and kW shares can be changed respectively by changing which of the following?
