Electrical Machines (Part-13)

What is the primary purpose of using permanent magnets in a motor?

A Generate torque
B Reduce losses
C Control speed
D Increase efficiency

What is the main cause of core losses in electrical machines?

A Copper losses
B Eddy currents
C Mechanical stress
D Friction

How are eddy current losses minimized in electrical machines?

A By using laminated cores
B By reducing speed
C By using copper windings
D By increasing the load

What effect does increasing the frequency have on core losses in electrical machines?

A Decreases efficiency
B No effect
C Increases losses
D Decreases losses

In a motor with permanent magnets, how does the magnetic field compare to conventional motors?

A Unstable
B Weaker
C Non‐existent
D Stronger

What is the primary cause of copper losses in electrical machines?

A Friction in bearings
B Armature resistance
C Core material
D Rotor resistance

How does increasing the core material’s permeability affect core losses?

A Increases efficiency
B No effect
C Increases losses
D Reduces losses

What role do permanent magnets play in brushless DC motors?

A Increase speed
B Control power supply
C Generate the magnetic field
D Reduce torque

What is the impact of high eddy current losses in an electrical machine?

A Reduced efficiency
B Increased torque
C Increased power factor
D Increased speed

What type of material is commonly used to reduce eddy current losses in electrical machines?

A Iron
B Copper
C Aluminum
D Silicon steel

How does the size of the air gap in a motor affect its efficiency?

A Increases efficiency
B Decreases efficiency
C No effect
D Increases torque

What is the main purpose of core laminations in electrical machines?

A Increase magnetic flux
B Improve efficiency
C Reduce mechanical stress
D Reduce eddy current losses

What effect does increasing the magnetic field strength have on core losses?

A Increases losses
B Increases efficiency
C Decreases losses
D No effect

How does the efficiency of a permanent magnet motor compare to conventional motors?

A Variable
B Higher
C Equal
D Lower

What is the primary advantage of using permanent magnets in a motor?

A Reduced cost
B Increased speed
C Improved efficiency
D Higher torque