Induction motors now a days use die cast aluminum rotor for which of the following reasons? 1
AAluminum is lighter than copper
BAluminum is cheaper than copper
CAluminum is easy to cast because of its low melting point and easily available
DAluminum has less resistivity than copper
#42📘 EE Pocket Reviewer RojasEasy
Which type of motors don't have a commutator?
AInduction motor
BShunt motor
CSeries motor
DRepulsion motor
#43📘 EE Pocket Reviewer RojasEasy
In which of the following starting methods is the starting current maximum?
AAutotransformer starting
BStar-delta starting
CDirect on line starting
DPart winding starting
#44📘 EE Pocket Reviewer RojasEasy
How is the rotor current of a three-phase induction motor related to the slip of the motor?
ADirectly proportional to the slip
BInversely proportional to the slip
CDirectly proportional to the square of the slip
DInversely proportional to the square of the slip
#45📘 EE Pocket Reviewer RojasEasy
A three-phase induction motor is running at a slip s (in decimal). What is the approximate efficiency of the rotor?
As
B1 + s
C1 − s
Ds − 1
#46📘 EE Pocket Reviewer RojasEasy
Which of the following conditions will give maximum voltage to the rotor of an induction motor?
AWhen its rotor is blocked
BWhen it is running at full load condition
CWhen it is running at no-load condition
DWhen it is running at overload condition
#47📘 EE Pocket Reviewer RojasEasy
Which of the following will reverse the direction of rotation of an induction motor?
AReverse the polarity of the rotor circuit
BUse a reverse power relay
CInterchange all three supply lines
DInterchange any two of the three supply lines
#48📘 EE Pocket Reviewer RojasEasy
What term refers to the difference between the synchronous speed and the actual rotor speed of an induction motor?
ARegulation
BBack lash
CLag
DSlip
#49📘 EE Pocket Reviewer RojasEasy
Which statement is not true regarding the skewing of the rotor bars in a squirrel cage induction motor?
AIt prevents cogging
BIt reduces motor hum
CIt will produce uniform torque
DIt increases the starting torque
#50📘 EE Pocket Reviewer RojasEasy
A wound rotor induction motor is not normally selected on the basis of which of the following reasons?
AHigh starting torque is the main consideration
BVariable speed operation is required
CCost is the main consideration
DAn external voltage is to be fed in the rotor
#51📘 EE Pocket Reviewer RojasEasy
What will happen to the synchronous speed if the frequency of the 3-phase supply to the stator of an induction motor is increased?
AIt will decrease
BIt will increase
CIt will remain the same
DNone of these
#52📘 EE Pocket Reviewer RojasEasy
In a three-phase induction motor, the rotor reactance under running condition is less than its value at standstill. This is due to the reduction of which of the following?
ARotor inductance
BNumber of stator poles
CRotor frequency
DRotor resistance
#53📘 EE Pocket Reviewer RojasEasy
What type of rotor is used by a double cage induction motor?
ASlip-ring type
BSquirrel-cage type
CCommutator type
DCombination of squirrel cage and slip ring types
#54📘 EE Pocket Reviewer RojasEasy
A wound rotor induction motor can be distinguished easily from the squirrel-cage induction motor by which of the following?
ADirection of rotation
BPresence of slip rings
CSize of frame
DDiameter of shaft
#55📘 EE Pocket Reviewer RojasEasy
An induction motor at standstill is similar to a transformer with the ____.
ASecondary being short circuited
BSecondary being open circuited
CLow voltage winding being open circuited
DLow voltage winding being short circuited
#56📘 EE Pocket Reviewer RojasEasy
How can the speed of an induction motor be increased?
ABy increasing the number of poles in the stator windings
BBy decreasing the number of poles in the stator windings
CBy decreasing the frequency of the stator supply
DBy increasing the resistance of the rotor circuit
#57📘 EE Pocket Reviewer RojasEasy
Which one is true about an induction motor?
AThe rotor runs at a speed equal to the speed of the stator field
BThe rotor runs at a speed which is always less than the speed of the stator field
CThe rotor runs faster than the stator field
DThe rotor speed is independent of the stator field speed
#58📘 EE Pocket Reviewer RojasEasy
For higher efficiency on a three-phase induction motor, the slip of the motor must be how much?
AEqual to zero
BEqual to one
CAs large as possible
DAs small as possible
#59📘 EE Pocket Reviewer RojasEasy
What will happen if a three-phase induction motor is designed with higher value maximum flux density?
AIt will have better full load power factor
BIt will have higher full load efficiency
CIt will have a higher starting torque
DIt will have a higher overload capacity
#60📘 EE Pocket Reviewer RojasEasy
What is the usual connection of the rotor windings of a 3-phase wound rotor induction motor?
