Which of the following types of rotors is best suitable for turbo alternators?
ASalient pole type
BNon-salient pole type or cylindrical rotor
CEither A or
DNone of these
Electrical Engineering · Question Bank
Alternators
94 of 157 questions match · page 3 of 5. Answer in your head first, then check the solution.
In an alternator, which of the following is affected by armature reaction?
ADriving speed of armature
BGenerated voltage per phase
CArmature copper loss
DOperating power factor
What is the usual connection of the armature windings of a three-phase alternator?
ADelta
BWye
CWye-delta
DDelta-wye
Which statement is true about an alternator operating at unity pf?
AGenerated emf is equal to the terminal emf
BGenerated emf is less than the terminal emf
CGenerated emf is more than the terminal emf
DEither B or C, depending on how big is the load
A 3-phase alternator is running with a phase sequence of ABC for its three output voltages. If the direction of rotation is reversed, the phase sequence will become which of the following?
AThe same phase sequence of ABC
BACB sequence
CBCA sequence
DNone of these
When an alternator connected to a bus bar is shut down, what happens to the bus bar voltage?
AThe voltage will decrease
BThe voltage will increase
CThe voltage will remain the same
DThe voltage will fall down to zero
When running under steady state conditions, which one represents the air gap field of the alternator?
AIt is stationary with respect to the stator
BIt is rotating at synchronous speed against the direction of rotor rotation
CIt is rotating at synchronous speed with respect to rotor
DIt is rotating at synchronous speed in the direction of rotor rotation
What do you mean by the phrase “synchronization” of alternators?
AConnecting alternators in parallel
BAdjusting excitation on alternators
CAdjusting input torque on alternators
DRunning alternators at their synchronous speed
What is the size of an alternator in comparison to a dc generator, assuming they have the same power ratings?
AThe alternator is bigger in size
BThe alternator is smaller in size
CBoth machines have the same sizes
DEither A, or B or
When two or more alternators are in parallel operation, their kVAR load share is changed by changing which of the following?
ADriving torque
BExcitation
CEither A or
DBoth A and B simultaneously
A synchronous generator is connected to a power station. What will happen if the excitation is increased?
AThe reactive power generated will decrease
BThe reactive power generated will increase
CThe active power generated will increase
DThe active power generated will decrease
Which of the following refers to the synchronous reactance of the alternator?
AThe sum of the armature reaction reactance and the leakage reactance
BA reactance connected in series with the alternator to reduce the fault current
CThe leakage reactance only
DThe reactance due to armature resistance
What is the reason why the voltage regulation of an alternator is larger than the voltage regulation of a dc generator?
ADue to large armature resistance
BDue to large leakage reactance
CDue to complex effect of the armature reaction
DAll of these
Salient rotor type for alternators are used in which of the following applications?
AHigh speed prime mover is available
BLow speed prime mover is available
CMedium speed prime mover is available
DEither B or
An AC generator is run at 10% overload. What will happen?
ANo danger will occur
BThe brushes will spark excessively
CThe circuit breaker will kick out
DThe generator power factor will increase
What is the purpose of the frame of an alternator?
AIt is used to ventilate the armature
BIt is used as a return path for the field flux
CIt is used to hold the armature stampings
DIt is used to protect the operator of the machine
What is the purpose of using damper windings in alternators?
ATo prevent hunting
BTo achieve synchronism
CTo reduce friction and windage
DTo prevent the alternator from power reversal
In an alternator, the magnitude of the various voltage drops depends on which of the following?
ALoad current
BPower factor of the load
CSquare of the load current
DPower factor x load current
If the driving power from the prime mover driving ' the alternator is lost but the alternator remains connected to the bus bars with its field still excited, what will happen?
AThe alternator will run as a synchronous motor and will rotate in the same direction
BThe alternator will run as a synchronous motor and will rotate in the opposite direction
CThe alternator will still run as a synchronous generator but with less efficiency
DThe alternator will overload and get burned
The voltage regulation of an alternator is negative when the alternator is serving what type of load pf?
AZero pf
BUnity pf
CLeading pf
DLagging pf
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