Induction and Synchronous Machines MCQs (Part-11)

What is the primary advantage of a three-phase system over a single-phase system for powering induction motors?

A Higher efficiency
B Reduced voltage
C More torque
D Simpler design

What is the primary reason for harmonic effects in induction motors?

A High voltage
B Non-linear loads
C Rotor speed
D Stator winding resistance

In a three-phase induction motor, what is the relation between the rotor speed and synchronous speed?

A Rotor speed is constant
B Rotor speed is the same
C Rotor speed is higher
D Rotor speed is lower

Why are harmonic currents undesirable in induction motors?

A They lower motor speed
B They increase power factor
C They reduce system efficiency
D They reduce slip

What is the primary reason for using a capacitor in single-phase induction motors?

A Improve power factor
B Create phase shift
C Increase torque
D Regulate speed

What is the primary benefit of using a three-phase system to power synchronous motors?

A Reduced harmonic distortion
B Constant voltage
C Higher starting torque
D Efficient load sharing

How do harmonics affect the power factor in an induction motor?

A Decrease power factor
B No effect on power factor
C Increase efficiency
D Increase power factor

What happens when a synchronous motor is overloaded in a three-phase system?

A It draws less current
B It loses synchronism
C It increases power factor
D It speeds up

How do harmonics affect the efficiency of a three-phase system?

A Harmonics improve power factor
B Harmonics increase efficiency
C Harmonics reduce efficiency
D Harmonics have no effect

In a three-phase induction motor, what is the purpose of the rotor bars?

A Create a magnetic field
B Induce current
C Control speed
D Generate power

Why is a three-phase system preferred for large motors?

A It reduces the need for starting equipment
B It is simpler
C It is less expensive
D It provides constant torque

What type of harmonic distortion is most commonly observed in induction motors?

A Current harmonics
B Voltage harmonics
C Magnetic harmonics
D Frequency harmonics

What is the role of the stator in a three-phase induction motor?

A Create a rotating magnetic field
B Generate torque
C Control speed
D Supply power to the rotor

How does the use of a three-phase system affect the efficiency of power transmission?

A Reduces voltage
B Decreases losses
C Increases losses
D No effect

What is the effect of harmonic currents on the insulation of induction motors?

A They reduce friction
B No effect on insulation
C They degrade insulation
D They improve insulation life