Induction and Synchronous Machines MCQs (Part-9)

What is the purpose of the excitation system in a synchronous motor?

A Increase efficiency
B Provide rotor magnetic field
C Control rotor speed
D Supply power

What is the effect of improper voltage regulation in a synchronous motor?

A Increased power factor
B Constant speed operation
C Speed instability
D Reduced load sharing

How does the excitation system affect the voltage regulation of a synchronous generator?

A It adjusts the output voltage
B It reduces core losses
C It increases torque
D It stabilizes the speed

What happens when the excitation of a synchronous motor is reduced?

A Efficiency improves
B Speed increases
C The motor becomes unstable
D The motor operates at sub-synchronous speed

In which operation is the voltage regulation of a synchronous motor most critical?

A At startup
B Under full load
C At no load
D At low speed

What is the relationship between excitation and power factor in synchronous motors?

A Higher excitation increases power factor
B Excitation has no effect on power factor
C Lower excitation increases power factor
D Higher excitation decreases power factor

How is the voltage regulation of a synchronous generator typically measured?

A By the load angle
B By the speed of the rotor
C By the armature current
D By the change in load

What is the effect of under-excitation in a synchronous motor?

A Increases load capacity
B Reduces rotor losses
C Decreases power factor
D Improves efficiency

What is the primary cause of voltage fluctuation in a synchronous generator under varying loads?

A Rotor speed variation
B Insufficient excitation
C Incorrect slip setting
D Over-excitation

What happens when a synchronous motor is overloaded?

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

How does excitation affect the stability of a synchronous generator?

A Higher excitation improves stability
B Excitation does not affect stability
C Lower excitation improves stability
D Excitation decreases stability

What is the primary role of the excitation system in a synchronous machine?

A Increase efficiency
B Maintain voltage stability
C Control rotor speed
D Adjust torque output

What happens if a synchronous motor runs at an excessively high excitation?

A It draws excessive current
B It stabilizes load sharing
C It runs at higher speed
D It improves voltage regulation

What is the primary characteristic of the voltage regulation of a synchronous generator?

A It is constant under varying load
B It increases with load
C It depends on excitation level
D It varies with speed

What would happen to the power factor of a synchronous motor with over-excitation?

A Power factor worsens
B Power factor improves
C Power factor remains constant
D Power factor becomes zero