Induction and Synchronous Machines MCQs (Part-10)

What effect do harmonic currents have on an induction motor?

A They improve efficiency
B They cause mechanical vibrations and increase heating
C They reduce the motor’s power factor
D They stabilize the motor’s performance

Which of the following is typically used to improve the power factor in an induction motor?

A Capacitor bank
B Rotor resistance
C External cooling system
D Damper winding

What is the role of the air gap in an induction motor?

A To allow for cooling of the rotor
B To reduce friction between the rotor and stator
C To provide insulation and allow magnetic flux transfer
D To prevent rotor damage

What is the primary effect of increasing the pole number in a synchronous motor on its speed?

A The motor speed increases
B The motor speed decreases
C The motor torque increases
D The motor power factor improves

What is the primary cause of core losses in an electrical machine?

A Friction in the bearings
B Eddy currents and hysteresis
C Voltage fluctuations
D Overloading

What is the impact of increasing the permeability of the core material in an induction motor?

A It reduces the power factor
B It increases the motor’s efficiency
C It reduces the slip
D It decreases the starting torque

Which of the following cooling methods is commonly used for large synchronous motors?

A Air cooling
B Oil cooling
C Water cooling
D Liquid nitrogen cooling

How does the air gap affect the flux distribution in an induction motor?

A A larger air gap reduces the flux density
B A larger air gap increases the flux density
C The air gap has no effect on flux distribution
D A larger air gap stabilizes the flux distribution

What is the primary function of performance testing in induction and synchronous machines?

A To measure the motor’s power factor
B To determine the motor’s efficiency under different load conditions
C To inspect insulation materials
D To check for mechanical wear

How does vibration analysis help in diagnosing faults in induction motors?

A By detecting overheating
B By identifying mechanical imbalances or misalignments
C By measuring the power factor
D By measuring the current waveform

What is the effect of harmonic currents in a three-phase induction motor?

A They increase motor speed
B They reduce efficiency and cause additional heating
C They improve power factor
D They stabilize the voltage supply

How does the field winding design affect a synchronous motor?

A It improves the motor’s efficiency
B It provides the rotor with a magnetic field
C It helps control the motor’s speed
D It reduces the motor’s power loss

What is the primary cause of core losses in an electrical machine?

A Friction in the bearings
B Eddy currents and hysteresis
C Voltage fluctuations
D Overloading

What is the impact of increasing the permeability of the core material in an induction motor?

A It reduces the power factor
B It increases the motor’s efficiency
C It reduces the slip
D It decreases the starting torque

Which of the following cooling methods is commonly used for large synchronous motors?

A Air cooling
B Oil cooling
C Water cooling
D Liquid nitrogen cooling

How does the air gap affect the flux distribution in an induction motor?

A A larger air gap reduces the flux density
B A larger air gap increases the flux density
C The air gap has no effect on flux distribution
D A larger air gap stabilizes the flux distribution

What is the primary function of performance testing in induction and synchronous machines?

A To measure the motor’s power factor
B To determine the motor’s efficiency under different load conditions
C To inspect insulation materials
D To check for mechanical wear

How does vibration analysis help in diagnosing faults in induction motors?

A By detecting overheating
B By identifying mechanical imbalances or misalignments
C By measuring the power factor
D By measuring the current waveform

What is the effect of harmonic currents in a three-phase induction motor?

A They reduce efficiency and cause additional heating
B They increase motor speed
C They improve power factor
D They stabilize the voltage supply

How does rotor dynamics affect the performance of a motor?

A It has no effect on motor performance
B It affects the stability and vibration characteristics of the motor
C It increases the motor’s speed
D It improves the efficiency of the motor