30 Questions
What does the term 'actuator' refer to in motion control systems?
The component that delivers the motion
In electric power based actuator category, which two components work together?
Motor and drive
What does the term 'drive' generically refer to in industry?
Power amplification and power supply components together
What type of motion control applications are discussed in the chapter?
High performance motion control applications involving closed loop position and velocity control
Which motor-drive technologies are discussed in the chapter?
DC motors (brush-type and brushless type) and drives
What type of step motors and drives are discussed in the chapter?
Permanent magnet step motors, hybrid step motors, along with full step, half step, and micro-stepping drives
What determines one of the magnetic fields essential to the operation of a motor?
Coil winding
How is commutation achieved in brushless DC motors?
Solid-state power transistors based on a rotor position sensor
In what types of applications are field-wound DC motors typically used?
High power applications
What is the main difference between double acting solenoids and proportional valves?
Control of displacement
What is the role of brush pair in brush-type DC motors?
Make contact with a commutator ring assembly on the rotor
What distinguishes distributed winding from concentrated winding in motors?
Spatial distribution of wire on the stator
What type of motor operates based on the principles of electromagnetism?
Permanent magnet DC (PMDC) motors
What determines the maximum power capacity of an actuator?
The maximum temperature it can operate at
Which type of motor does not require a position sensor for basic position control?
Step motors
In which quadrants does a motor produce positive mechanical power output in motoring mode?
Quadrants I and III
What feature distinguishes brushless DC motors from conventional motors?
Lack of commutators and brushes
What is the operating principle of solenoids based on?
The tendency of the ferromagnetic plunger and coil-generated magnetic flux to seek the minimum reluctance point
Which type of motor is widely used for constant speed applications?
AC induction motors
What can solenoids provide in terms of motion?
Pull or push motion
What type of motor design allows for constant speed in steady-state and reduced speed variation as load torque varies?
Synchronous motors
What do electric actuators convert electrical energy into?
Mechanical form
What determines the torque capacity in step motors?
The air gap between the stator and rotor
What type of losses do electric actuators experience?
Resistance, core, friction, and windage
What physical phenomena do electric motors operate based on?
Magnetic attraction and repulsion
What components are found in every electric motor?
Rotor, stator, housing, bearings, and components for current commutation
What is the input and output in the conversion of electrical power to mechanical power in electric motors?
Input: voltage and current; Output: mechanical torque and speed
How do AC motors and DC motors behave in terms of speed applications with advances in power electronics?
AC motors can behave like DC motors
How is torque generation achieved in AC motors?
Through the interaction of two magnetic fields set up by the excitation current on the stator and induced in the rotor conductors
What is the proportionality constant for torque production in an electric motor dependent on?
The motor size and design parameters, and related to the strength of the magnetic flux vectors and the angle between them
Study Notes
Electric Motor Operating Principles and Components
- Electric motors operate based on three physical phenomena: magnetic attraction and repulsion, magnets seeking to minimize reluctance to magnetic flux, and current-carrying conductors creating electromagnets.
- Every motor consists of a rotor, stator, housing, bearings, and components for current commutation, such as a commutator and brush assembly in brush-type motors or rotor position sensors in brushless motors.
- AC induction motors have traditionally been used in constant speed applications, while DC motors have been used in variable speed applications, but advances in power electronics allow AC motors to behave like DC motors.
- Electric motors convert electrical power to mechanical power, with the input being voltage and current, and the output being mechanical torque and speed.
- In DC motors, one magnetic field is due to the current through the armature winding on the rotor, while the other is due to the permanent magnets in the stator or field excitation of the stator winding.
- AC motors generate torque through the interaction of two magnetic fields: one set up by the excitation current on the stator and the other induced in the rotor conductors.
- In both DC and AC induction motors, the two magnetic fields are maintained at a 90-degree angle to maximize torque generation capability per unit current.
- Stepper motors work on the same principle as brushless DC motors, with a given stator excitation state defining a stable rotor position due to the attraction between electromagnetic poles of the stator and permanent magnets of the rotor.
- Torque generation in any electric motor results from the interaction of two magnetic flux density vectors: one generated by the stator and one generated by the rotor, and the torque production is proportional to the strength of these vectors and the sine of the angle between them.
- Every motor requires some form of current commutation to modify the direction and magnitude of current in the windings as a function of rotor position, in order to efficiently produce torque.
- The design of an electric motor seeks to determine the three-dimensional shape of the effective magnetic reluctance, the distribution of coil wires, and the permanent magnets' characteristics.
- The proportionality constant for torque production in an electric motor depends on the motor size and design parameters, and it is related to the strength of the magnetic flux vectors and the angle between them.
Test your knowledge of electric motor operating principles and components with this quiz. Explore the key physical phenomena behind motor operation, the components involved, and the principles governing torque generation in both AC and DC motors.
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