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
Electrical Engineering · Question Bank
3P Induction Motors
115 of 135 questions match · page 5 of 6. Answer in your head first, then check the solution.
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
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
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
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
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
What is the usual connection of the rotor windings of a 3-phase wound rotor induction motor?
AStar
BDelta
CStar-delta
DSeries-parallel
When is cogging in an induction motor occurs?
AIt occurs at high voltage when the number of stator teeth and rotor teeth are equal
BIt occurs at high voltage and when the number of stator teeth and rotor teeth are not equal
CIt occurs at low voltage when the number of stator teeth and rotor teeth are equal
DIt occurs at low voltage and when the number of stator teeth and rotor teeth are not equal
An induction motor works with what type of supply voltage?
ADC only
BAC only
CBoth AC and DC
DNone of these
In a squirrel cage induction motor, the number of rotor bars is generally
AAn even number
BEqual to the stator poles
CA prime number
DNone of these
Which of the following method is used to vary the speed of a squirrel cage induction motor?
ABy pole changing
BBy rheostatic control
CBy varying supply voltage
DBy cascade control
What will happen if the rotor of a squirrel cage induction motor is open?
AThe motor runs at very high speed
BThe motor will not run
CThe motor will run at very low speed
DThe motor will run at normal speed but noisy
What is the usual range of the full load slip of a three-phase induction motor?
A10% to 20%
B2% to 5%
C20% to 30%
D80% to 95%
In a three-phase induction motor, what is the relative speed between the stator flux to the rotor flux?
AZero
BEqual to the synchronous speed
CEqual to the slip speed
DEqual to the rotor speed
What is the slip of an induction motor at no load?
AInfinite
BAbout 5 to 10%
COne
DPractically zero
A three-phase induction motor is running at slip s (in decimal). What is the rotor output?
A(1 + s) × (rotor input)
B(s) × (rotor input)
C(1 − s) × (rotor input)
D(1/s) × (rotor input)
With an increase in supply voltage of an induction motor, which of the following will also increase?
AOperating power factor
BSlip
CTorque
DAll of these
The direction of rotation of the field in a three-phase induction motor is dependent on which of the following?
ANumber of poles
BSupply voltage
CSupply frequency
DPhase sequence of supply voltage
A wound rotor induction motor is mainly used in which of the following conditions?
AWhen speed control is not required
BWhen cheaper motor is required
CWhen high starting torque is required
DWhen high rotor resistance is required
The speed of a three-phase wound rotor induction motor can be increased by which of the following methods?
ABy increasing the supply voltage
BBy decreasing the supply voltage
CBy decreasing the external resistance in the rotor circuit
DBy increasing the external resistance in the rotor circuit
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