An induction motor at no load 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
Electrical Engineering · Question Bank
3P Induction Motors
88 of 135 questions match · page 2 of 5. Answer in your head first, then check the solution.
A three-phase wound motor is otherwise called what motor?
ASynchronous motor
BSlip ring motor
CSeries motor
DStepper motor
What is the slip of an induction motor at standstill?
AZero
BOne
CInfinity
DUndefined
A three-phase induction motor is running at half of its rated load. What will happen if one of the line fuses gets opened?
AThe motor will immediately stop running
BThe motor will continue to run at the same speed
CThe motor will continue to run at slightly lesser speed
DThe motor will continue to run at an increased speed
Two induction motors A and B are identical except that the air gap of A is 50% greater than that of B. Which of the following statements is true?
AThe no-load pf of A is better than that of B
BThe no-load pf of A is poorer than that of B
CThe core losses of A are more than those of B
DThe operating flux of A will be smaller than that of B
A very large 3-phase induction motor is started using which of the following?
AStar-delta starting
BDOL starting
CAutotransformer starting
DPart winding starting
What is the effect of the magnetizing current drawn by an induction motor to its operating power factor
AIt makes the pf lagging
BIt makes the pf leading
CIt makes the pf unity
DIt makes the pf zero
The term “cogging” is normally associated to what type of motors?
AInduction motor
BDC series motor
CDC shunt motor
DRepulsion motor
The speed of an induction motor is comparable to which of the following dc motors?
ASeries motor
BShunt motor
CLong shunt compound motor
DShort shunt compound motor
The stator and rotor cores of an induction motor are made up of magnetic materials. Why?
ATo keep the cost of construction low
BTo make the parts strong
CTo reduce the magnetizing current
DTo increase the reluctance of the magnetic path
The slip rings for induction motors are made from which of the following materials?
AAluminum
BPhosphor bronze
CCarbon
DCobalt steel
Which one is true about the power factor of a squirrel cage induction motor?
AIt is low at light loads only
BIt is low at heavy loads only
CIt is low at rated load only
DIt is low at any loads
What is the reason why it is advisable to avoid direct on line starting of a large induction motor?
AThe starting torque is too high
BThe motor might run in the wrong direction
CThe motor will pick up speed dangerously
DThe motor takes dangerously high current
The principle of operation of an induction motor is similar to which of the following?
ASynchronous motor
BRepulsion start induction motor
CCapacitor-start induction run
DTransformer with shorted secondary
Which one is true about the torque developed by a three-phase induction motor?
AIt is directly proportional to the rotor resistance
BIt is directly proportional to the square of the supply voltage
CIt is inversely proportional to the supply voltage
DIt is inversely proportional to the slip
What type of field is produced by the stator of a three-phase induction motor?
ASteady
BSinusoidal
CRotating
DAlternating
Which one is true about an induction motor?
AIt is an essentially constant speed motor
BIt is a variable speed motor
CIt is a very costly motor
DIt is a motor that requires higher maintenance
Which of the following is the source of power of the rotor of an induction motor?
AAC supply voltage
BExternal exciter
CCentrifugal switch
DMagnetic induction
The fractional slip of an induction motor is the ratio of which of the following?
ARotor copper loss to rotor input
BStator copper loss to stator input
CRotor copper loss to rotor output
DRotor copper loss to stator copper loss
Which of the following is a reason why the losses in the rotor of an induction motor are less than the losses in the stator?
ALess rotor frequency
BSlots in the rotor are skewed
CRotor diameter is small
DNone of these
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