Dc Motor Quiz Flashcards
(26 cards)
How is AC motor speed controlled?
Through frequency
AC motor speed control is achieved by varying the frequency of the AC supply.
How is DC motor speed controlled?
Through current
The speed of a DC motor can be adjusted by changing the amount of current flowing through it.
What is the purpose of a rectifier?
Converts AC to DC
A rectifier is used to convert alternating current into direct current.
What is the purpose of an inverter?
Converts DC to AC
An inverter changes direct current into alternating current.
What are the disadvantages of DC motors?
More complex, costly, and require maintenance
Compared to AC motors, DC motors have higher complexity and maintenance needs.
What are the advantages of DC motors in terms of speed control?
Easy to control speed with simple controllers
DC motors can be easily managed for speed adjustments using basic control mechanisms.
What are the two types of DC motors?
- Brushed
- Brushless
Brushed motors use carbon brushes for current transfer, while permanent magnet motors rely on fixed magnets.
How does an armature function in a DC motor?
Rotating portion that gets current from carbon brushes that ride on the commutator
The armature is essential for converting electrical energy into mechanical energy.
What is a wound field in a DC motor?
Stator has poles (windings) that create a magnetic field
The wound field consists of coils that generate a magnetic field when current passes through them.
What are the three types of Wound Field Motors?
- Series (A/S)
- Shunt (A/F)
- Compound (A/S/F)
Each type has distinct characteristics in terms of torque and speed control.
Describe Series Wound Field Motor (A/S).
Windings in series with armature, high torque, no speed control
Commonly used in applications requiring high torque, like traction motors.
Describe Shunt Wound Field Motor (A/F).
Windings in parallel with armature, low torque rating, great speed control
This type is used where speed regulation is more critical than torque.
Describe Compound Wound Field Motor (A/S/F).
Combination of Series and Shunt windings, best of both, speed varies little with load
It provides a balance between torque and speed control.
What characterizes Brushless DC motors?
Fixed magnets in the rotor, wound field in the stator, capable of high RPM(1800)
20 HP and below
Brushless motors are efficient and can achieve high speeds while requiring less maintenance.
What is the typical power range for Brushless DC motors?
20 HP and Below
Brushless motors are generally used for applications where power requirements do not exceed this range.
2 types of DC brushed motors
Permanent magnet 🧲
Wound field
Permanent magnet 🧲 HP ratings
1/4 - 5 HP
*Has fixed magnets in the stator
Stator has poles (windings) that we pass current through to create a magnet field
Wound field
* 3 types
Series
Shunt
Compound
Windings in series with the armature
Series
Windings in parallel with the armature
Shunt
Combination of series and shunt windings
Compound
What type of motor is capable of high RPMs? (1800)
Brushless
What motor has high torque, no speed control, used for traction motors/metal rolling?
Series motors
What motor has great speed control, lower torque and operates from a different power source than the armature?
Shunt
