300 Important Alternator MCQ Question and Answer | PDF Free Download
1.The rating of the prime mover driving an alternator is determined entirely by its ____rating.
- AVoltage
- BCurrent
- CKW output
- Dspeed
2.When an alternator designed for operation at 60 Hz is operated at 50 Hz
- AkVA rating will increase in the ratio of 1:2
- Boperating voltage will reduce in the ratio of 5/6
- Coperating voltage will increase in the ratio of 1:2
- Doperating voltage will reduce in the ratio of (5/6)2
3.The rating of a synchronous machine is usually governed by its
- ASpeed
- BTemperature rise
- CWeight
- DNone of these
4.The flux set up by the armature current, which does not cross the air gap and takes a different path is called the ____flux
- ALeakage
- BMain
- CCross magnetizing
- DDemagnetizing
5.The magnitude of leakage flux of an alternator depends on
- AThe magnitude of armature current
- BPhase angle between armature current and terminal voltage
- CAir gap thickness
- DBoth (a) and (b)
6.Leakage reactance of the armature of a salient pole synchronous machine which varies with the position of rotor is due to leakage flux
- AOf end connections
- BWhich comes out of slot teeth, crosses the air gap and enters the pole faces
- CWhich remains within the slot
- DNone of the above
12.In a synchronous generator
- AThe armature mmf leads the air gap flux and air gap flux leads the field mmf
- BThe armature mm leads the air gap flux and the air gap flux lags behind the field mmf
- CThe armature mmf lags behind the air gap flux and airgap flux lags behind the field mmf
- DThe armature mmf lags behind the air gap and air gap flux leads the field mmf.
13.Armature reaction effect is / are ____on the main field flux
- ADistorting (or cross magnetizing) as well as demagnetizing
- BOnly assisting
- COnly demagnetizing
- DOnly distorting
14.The armature reaction effect in a synchronous machine depends on
- ALoad current
- BPower factor of the load
- CSpeed of the machine
- DBoth (a) and (b)
15.In a synchronous generator, the effect of cross magnetization is to make the generated voltage
- ATruly sinusoidal
- BNon sinusoidal
- CFree from harmonics
- DNone of these
16.In an alternator, the armature mmf will be in phase with the main field flux only when the load is purely
- AResistive
- BInductive
- CCapacitive
- DNone of the above
17.In an alternator, the armature reaction is considered to be equivalent to a fictitious
- AReactance
- BResistance
- CImpedance
- DAdmittance
18.A synchronous generator is feeding a zero-power factor (lagging) load at rated current. The armature reaction is
- AMagnetizing
- BDemagnetizing
- CCross magnetizing
- DIneffective
19.Armature reaction AT of a synchronous generator supplying power at rated voltage with zero power factor lagging is
- AMagnetizing
- BDemagnetizing
- CCross magnetizing
- DBoth magnetizing and cross magnetizing
20.The synchronous reactance in an alternator is the
- AReactance due to armature reaction of the machine
- BReactance due to leakage flux
- CCombined reactance due to leakage flux and armature reaction
- DReactance either due to armature reaction or leakage flux