Engineering
Engineering MCQs With Answers
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Inverted V-curves of a synchronous motor represent the plot between:
ASupply voltage and frequency
BArmature current and field current
CArmature current and power factor
DPower factor and field current
Swinburne’s test is a convenient indirect method used to determine no-load losses and efficiency of:
A1-phase Transformers
BDC shunt and compound machines
C3-phase Alternators
DDC series motors only
In a 3-phase synchronous motor, damper windings (pole face windings) are provided to:
AIncrease field excitation
BEliminate eddy currents
CReduce armature reaction
DPrevent hunting and provide starting torque
The speed-torque characteristic of a DC series motor closely resembles a:
AParabola opening upwards
BHorizontal straight line
CStraight line through origin
DRectangular hyperbola
Why should a DC series motor NEVER be started under no-load conditions?
AIt will attain dangerously high speed
BIt will fail to start
CIt will reverse its direction of rotation
DIt will burn out due to low current
The phenomenon of ‘crawling’ in a 3-phase induction motor is primarily caused by:
AUnbalanced supply voltage
B3rd time harmonics
C5th space harmonics in the air-gap field
D7th space harmonics in the air-gap field
The phenomenon of ‘cogging’ in an induction motor refers to:
AVibrations in shaft bearings
BHigh starting current
CMagnetic locking between stator and rotor teeth
DMotor running at 1/7th speed
Schering bridge is primarily employed for the measurement of:
AMutual inductance
BFrequency
CCapacitance and dielectric dissipation factor
DLow resistance
The slip of a 3-phase induction motor at the moment of starting is equal to:
A0.05
B0.0
CInfinity
D1.0
Which AC bridge is specifically suited for measuring inductance with a high Quality factor (Q > 10)?
AMaxwell's Bridge
BWien Bridge
CHay's Bridge
DSchering Bridge