The synchronous impedance of an alternator is defined as the ratio of which of the following?
AShort circuit voltage to short circuit current
BOpen circuit voltage to open circuit current
CShort circuit voltage to open circuit current
DOpen circuit voltage to short circuit current
#62📘 EE Pocket Reviewer RojasEasy
In an alternator, the flux created by the armature mmf subtracts directly from the main flux for which of the following condition of load?
ALoad pf is zero leading
BLoad pf is zero lagging
CLoad pf is unity
DLoad pf is 0.8 lagging
#63📘 EE Pocket Reviewer RojasEasy
The voltage of the field windings of an alternator is usually what value?
ALess than 200
BBetween 200 V and 440
CBetween 440 V and 1 kV
DMore than 1 kV
#64📘 EE Pocket Reviewer RojasEasy
A three-phase synchronous generator is operating at 0.8 pf lagging with respect to the excitation voltage. What is the nature of the mmf produced by the armature current?
AIt has magnetizing effect
BIt has demagnetizing effect
CIt has cross-magnetizing effect only
DIt has partly demagnetizing and partly cross-magnetizing effects
#65📘 EE Pocket Reviewer RojasEasy
Under what load power factor will the armature flux cross magnetizes the main field flux?
AZero pf
BUnity pf
CLeading pf
DLagging pf
#66📘 EE Pocket Reviewer RojasEasy
Two alternators are operating in parallel, if the load shared by one of the alternators is to be increased, what will the operator do the alternator?
AKeep its input torque constant and increase its excitation
BDecrease its excitation and input torque simultaneously
CKeep the excitation constant and increase its input torque
DNone of these
#67📘 EE Pocket Reviewer RojasEasy
For proper parallel operation alternators, which of the following alternator ratings must be the same?
ARated speed
BVoltage rating
CExcitation
DkVA rating
#68📘 EE Pocket Reviewer RojasEasy
The slip rings employed in a three-phase alternator in a hydro station are insulated for which of the following voltage levels?
ALow voltage
BHigh voltage
CExtra high voltage
DVery low voltage
#69📘 EE Pocket Reviewer RojasEasy
What is the advantage of distributing the windings in an alternator?
AIt will reduce harmonics
BIt will prevent vibrations
CIt will save on copper wires
DIt will improve voltage waveform
#70📘 EE Pocket Reviewer RojasEasy
What is an exciter?
AA synchronous generator
BA dc shunt generator
CA synchronous motor run without a load
DA dc shunt motor run without a load
#71📘 EE Pocket Reviewer RojasEasy
Two alternators A and B are operating in parallel sharing equally a lagging pf load. If the excitation of alternator A is increased, what happens to the current delivered by each alternators?
AAlternator A will deliver more current than
BAlternator A will deliver lesser current than
CAlternators A and B will continue to deliver the same amount of current as before
DNone of these
#72📘 EE Pocket Reviewer RojasEasy
As the load power factor of an alternator becomes more leading, what will happen to the generated voltage required to give rated terminal voltage?
AIt will decrease
BIt will increase
CIt will remain the same
DIt will become unpredictable
#73📘 EE Pocket Reviewer RojasEasy
In alternators, the so-called “dark and bright lamp” method is used for which of the following?
ADetermining the operating phase sequence
BDetermining voltage regulation at a given load
CIn transferring load between alternators
DIn synchronizing alternators
#74📘 EE Pocket Reviewer RojasEasy
Which of the following prime movers of an alternator do not have the tendency to hunt?
AHydraulic turbines
BDiesel engines
CSteam turbines
DAll of these
#75📘 EE Pocket Reviewer RojasEasy
The power factor of an alternator is determined from which of the following?
AExcitation
BPrime mover
CLoad
DSpeed
#76📘 EE Pocket Reviewer RojasEasy
An over-excited alternator is operating under what load power factor?
ALeading pf
BZero pf
CLagging pf
DUnity pf
#77📘 EE Pocket Reviewer RojasEasy
Two identical alternators A and B are running in parallel sharing equally a common load. If the excitation of alternator B is increased without changing its steam supply, then ____
AkVAR supplied by B will decrease
BkW supplied by B will be almost the same
CkVA supplied by B will decrease
DPower factor of B will increase
#78📘 EE Pocket Reviewer RojasEasy
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
#79📘 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
#80📘 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?
