26 Part III: AC Motors – Harnessing the Flow – Review Questions
(PC: “Hand holding magnifying glass among a lot of questions. Finding answers to questions and solving problems” by wuestenigel is licensed under CC BY 2.0.)
Questions to review:
1. Multiple Choice: AC motors and DC motors are both fundamental building blocks in automation. What is the key difference in their power source? a) AC motors operate on a constant voltage source, whereas DC motors require a varying voltage. b) AC motors utilize a sinusoidal AC waveform, while DC motors rely on a constant DC voltage. c) AC motors are generally less efficient than DC motors. d) AC motors require more complex control circuits compared to DC motors.
2. Short Answer: Explain the basic principle behind the operation of an AC induction motor. How does the rotating magnetic field within the motor induce current flow in the rotor?
3. Application Problem: A ventilation system in a building requires an AC motor to efficiently power a large exhaust fan. Considering the key functionalities, which AC motor type (single-phase, split-phase, two-capacitor, three-phase) would likely be the best choice for this application, and why?
4. Challenge Question: Imagine you are designing an electric car. How could AC motor control techniques, such as variable frequency drives (VFDs), be beneficial for optimizing vehicle performance?
5. True or False: Transformers can only be used to increase the voltage of an AC power supply.
6. Open Ended: Discuss the advantages and disadvantages of using single-phase AC motors compared to three-phase AC motors for industrial automation applications.
7. Matching: Match the following AC motor types with their corresponding applications:
a) Single-phase induction motor
b) Three-phase induction motor
c) AC servo motor
d) Synchronous motor
i) Precise control of speed and position in robotic arms
ii) Powering industrial machinery requiring high starting torque
iii) Commonly used in household appliances like washing machines
iv) Maintaining constant speed for generators or large clocks
8. Design Challenge: You are tasked with designing a system to control the speed of a conveyor belt driven by an AC motor. Describe two different approaches to achieve this using AC motor control techniques, and discuss the advantages and disadvantages of each method.
9. Think-Like-an-Engineer: Electrical safety is paramount when working with AC motors. Why is it important to understand the concept of power factor in AC motor applications, and how can power factor correction techniques improve safety and efficiency?
10. Research and Report: Choose a specific application of AC motors mentioned in the module (e.g., wind turbines, high-speed trains) and research the additional control systems used to ensure safety and optimize motor performance in that application. Prepare a short report summarizing your findings.