Author: Rakesh Parekh Microchip Technology Inc. created naturally in the stator because of the nature of the supply. DC motors depend either on mechanical or electronic commutation to create rotating magnetic fields. A single-phase AC induction motor depends on extra electrical components to produce this rotating magnetic field. Two sets of electromagnets are formed inside any motor. In an AC induction motor, one set of electromagnets is formed in the stator because of the AC supply connected to the stator windings. The alternating nature of the supply voltage induces an Electromagnetic Force (EMF) in the rotor (just like the voltage. | c Microchip AN887 AC Induction Motor Fundamentals Author Rakesh Parekh Microchip Technology Inc. INTRODUCTION AC induction motors are the most common motors used in industrial motion control systems as well as in main powered home appliances. Simple and rugged design low-cost low maintenance and direct connection to an AC power source are the main advantages of AC induction motors. Various types of AC induction motors are available in the market. Different motors are suitable for different applications. Although AC induction motors are easier to design than DC motors the speed and the torque control in various types of AC induction motors require a greater understanding of the design and the characteristics of these motors. This application note discusses the basics of an AC induction motor the different types their characteristics the selection criteria for different applications and basic control techniques. BASIC CONSTRUCTION AND OPERATING PRINCIPLE Like most motors an AC induction motor has a fixed outer portion called the stator and a rotor that spins inside with a carefully engineered air gap between the two. Virtually all electrical motors use magnetic field rotation to spin their rotors. A three-phase AC induction motor is the only type where the rotating magnetic field is created naturally in the stator because of the nature of the supply. DC motors depend either on mechanical or electronic commutation to create rotating magnetic fields. A single-phase AC induction motor depends on extra electrical components to produce this rotating magnetic field. Two sets of electromagnets are formed inside any motor. In an AC induction motor one set of electromagnets is formed in the stator because of the AC supply connected to the stator windings. The alternating nature of the supply voltage induces an Electromagnetic Force EMF in the rotor just like the voltage is induced in the transformer secondary as per Lenz s law thus generating another set of electromagnets .
