TAILIEUCHUNG - Chapter 1: Background

In this introductory chapter, a general characterization of induction motors and their use in ac drive systems is given. Common mechanical loads and their characteristics are presented, and the concept of operating quadrants is explained. Control methods for induction motors are briefly reviewed. | BACKGROUND In this introductory chapter a general characterization of induction motors and their use in ac drive systems is given. Common mechanical loads and their characteristics are presented and the concept of operating quadrants is explained. Control methods for induction motors are briefly reviewed. INDUCTION MOTORS Three-phase induction motors are so common in industry that in many plants no other type of electric machine can be found. The author remembers his conversation with a maintenance supervisor in a manufacturing facility who when asked what types of motors they had on the factory floor replied Electric motors of course. What else As it turned out all the motors hundreds of them were of the induction squirrel-cage type. This simple and robust machine an ingenious invention of the late nineteenth century still maintains its unmatched popularity in industrial practice. I 2 CONTROL OF INDUCTION MOTORS Induction motors employ a simple but clever scheme of electromechanical energy conversion. In the squiưel-cage motors which constitute a vast majority of induction machines the rotor is inaccessible. No moving contacts such as the commutator and brushes in de machines or slip rings and brushes in ac synchronous motors and generators are needed. This arrangement greatly increases reliability of induction motors and eliminates the danger of sparking permitting squirrel-cage machines to be safely used in harsh envữonments even in an explosive atmosphere. An additional degree of ruggedness is provided by the lack of wiring in the rotor whose winding consists of uninsulated metal bars forming the squirrel cage that gives the name to the motor. Such a robust rotor can run at high speeds and withstand heavy mechanical and electrical overloads. In adjustable-speed drives ASDs the low electric time constant speeds up the dynamic response to control commands. Typically induction motors have a significant torque reserve and a low dependence of speed on the load .

• Điện - Điện tử
• Drive systems with induction motors
• Control of induction motors
• Chapter 1 background
• Chapter 1 induction motors
• Characterization of induction motors
• AC drive systems
• Use in AC drive systems
• transformers
• power electronic
• machinery fundamentals
• synchronous generation
• synchronous motor
• induction motors