300 Important Alternator MCQ Question and Answer | PDF Free Download
1.Drop in terminal voltage of an alternator due to armature reaction is countered by
- ADamper winding
- BEffect of saliency
- CIncreased prime mover output
- DAutomatic voltage regulator
2.The saturated synchronous reactance of an alternator is _____its unsaturated synchronous reactance
- AMore than
- BLess than
- CEqual to
- DNone of these
3. In an alternator, short circuit current is limited by
- ASaturated synchronous impedance
- BUnsaturated synchronous impedance
- CEither of the above
- DNone of these
4.When the load (inductive) is thrown off, the terminal voltage will
- AIncrease
- BDecrease
- CRemain unchanged
- DNone of these
5.As the leading power factor of the load of an alternatordecreases, the magnitude of generated voltage required to give rated terminal voltage
- AIncreases
- BDecreases
- CRemains unchanged
- DNone of the above
6. In a synchronous generator delivering lagging power factor load
- AThe excitation emf leads terminal voltage by the power angle
- BThe excitation emf lags the terminal voltage by the power angle
- CExcitation emf leads the terminal voltage by the power factor angle
- DNone of the above
7.The power factor on which an alternator operates depends on the
- ASpeed of the prime mover
- BNature of the load being supplied
- CArmature losses
- DCopper losses
8.Unbalanced 3-phase stator currents cause
- AVibrations
- BHeating of rotor
- CDouble frequency currents in the rotor
- DAll of the above
9.Regulation of an alternator supplying resistive or inductive load is
- AAlways +ve
- BAlways -ve
- CEither of the above or zero
- DNone of the above
10.A leading pf load on an alternator implies that its voltage regulation shall be
- APositive
- BNegative
- CZero
- DAny one of these
11.The effect of leading power factor on the voltage regulation of an alternator is
- AIncreasing in nature
- BDecreasing in nature
- CMaintained at constant value
- DOscillating in nature
12.The leakage reactance of a three-phase alternator is determined by performing
- AOpen circuit and zero power factor tests
- BZero power factor and slip tests
- COpen and short circuit tests
- DShort circuit and slip tests
13.The synchronous impedance method of finding the voltage regulation of a cylindrical rotor alternator is generally considered as
- AA pessimistic method because saturation is not considered
- BAn optimistic method because saturation is not considered
- CA fairly accurate method even if power factor is not taken into account while determining synchronous impedance
- DA fairly accurate method when power factor is taken into account while determining synchronous impedance
14.The regulation obtained by synchronous impedance method in an alternator is always higher than actual value because
- ASynchronous reactance is assumed variable while it is not
- BEffective armature resistance is assumed constant
- CSynchronous reactance is assumed constant while it is not
- DField current is increased to give short circuit current about twice of full load current.
15.The short circuit characteristics of an alternator is
- AAlways linear
- BAlways nonlinear
- CEither of (a) and (b)
- DNone of these
16.Under short-circuit conditions, the power factor of an alternator is
- AUnity
- BAlmost zero lagging
- CAlmost zero leading
- DNone of the above
17.The zero-power factor characteristic for the Potier diagram can be obtained by loading the synchronous generator using
- ALamp load
- BSynchronous motor
- CWater load
- DDC motor
18.Modern alternators are designed to have poor regulation as it
- AIncreases the value of short circuit current
- BLimits the value of short circuit current
- CIncreases the efficiency of operation
- DBoth (a) and (c)
19.Armature reaction mmf and leakage reactance of a synchronous machine are determined by
- AOpen circuit and short circuit tests
- BOpen circuit and Zero Power factor Test
- COpen circuit test only
- DZero pf test only
20.Which of the following methods would give higher than actual value of regulation of an alternator?
- AZPF method
- BMMF method
- CEMF method
- DASA method