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WorksheetsMCQ Quiz: Electrical Drives (From PPT)
Total questions: 30
Worksheet time: 15mins
Electrical drives in CNC machines are mainly used for:
Material handling
Position and speed control
Storage control
Tool inspection
Electrical drives used in CNC machines are generally:
Large and complex
Small in size and easy to control
Pneumatic driven
Manually operated
Electrical motors are classified into:
Servo and stepper motors
AC motors and DC motors
Hydraulic and pneumatic motors
Single-phase and three-phase motors
A DC motor converts:
AC electrical energy into mechanical energy
Mechanical energy into electrical energy
DC electrical energy into mechanical energy
Heat energy into mechanical energy
A brushed DC motor mainly consists of:
Rotor, stator, slip rings
Armature, commutator, brushes
Permanent magnet and encoder
Windings and transformer
The magnetic field in a brushed DC motor is produced by:
Permanent magnets only
Electromagnets
Batteries
Hall sensors
The main function of a commutator is to:
Increase torque
Reduce friction
Reverse the direction of current
Control voltage
In a brushed DC motor, brushes remain:
Rotating
Stationary
Electrically isolated
Magnetized
Brushless DC motors eliminate:
Stator windings
Rotor magnets
Brushes and commutator
Control electronics
In brushless DC motors, current switching is done by:
Slip rings
Mechanical contacts
Transistors
Carbon brushes
Rotor position in brushless DC motors is sensed using:
Tachogenerators
Encoders
Hall effect sensors
Proximity switches
One advantage of brushless DC motors is:
High noise
Mechanical commutation
Reduced wear
Poor efficiency
AC motors convert:
DC current into rotation
AC current into rotation
Mechanical energy into electrical energy
Heat into motion
The main limitation of AC motors compared to DC motors is:
Low torque
Difficult speed control
High maintenance
Low power rating
Speed control of AC motors is achieved using:
Transformers
Rectifiers
Variable Frequency Drives
Commutators
AC motors are classified into:
Series and shunt motors
Synchronous and induction motors
Servo and stepper motors
Single-phase and DC motors
A synchronous motor runs at:
Variable speed
Speed higher than supply frequency
Constant speed fixed by supply frequency
Zero speed at no load
Synchronous motors require:
AC excitation
DC excitation
No excitation
Battery supply only
The stator of a synchronous motor produces:
Static magnetic field
Rotating magnetic field
Pulsating magnetic field
Weak magnetic field
Induction motors work on the principle of:
Magnetic repulsion
Electrostatic force
Electromagnetic induction
Mutual attraction
In an induction motor, rotor current is:
Supplied externally
Generated by DC supply
Induced by stator magnetic field
Supplied through commutator
A squirrel-cage rotor consists of:
Permanent magnets
Copper or aluminum bars
Armature windings
Slip rings only
A three-phase induction motor is:
Not self-starting
Self-starting
Battery operated
Manually started
Stepper motors are best suited for:
High-speed continuous operation
Open-loop position control
Heavy load transmission
High power applications
A stepper motor rotates in response to:
Continuous AC voltage
Mechanical force
Electrical pulses
Hydraulic pressure
Variable reluctance stepper motors have:
Permanent magnet rotor
No permanent magnet in rotor
High detent torque
Encoder feedback
Permanent magnet stepper motors typically have:
Zero torque
Step angle between 7.5° and 15°
Very high speed
No magnetic field
Hybrid stepper motors combine features of:
AC and DC motors
Servo and induction motors
Variable reluctance and permanent magnet motors
Single-phase and three-phase motors
Servomotors are mainly used in:
Open-loop systems
Closed-loop control systems
Hydraulic systems
Manual machines
Feedback devices used in servo systems include:
Transformers
Encoders or resolvers
Limit switches
Relays
