AC Motor Types

An AC motor is a type of electric motor that operates on alternating current. AC motors are widely used in various applications due to their simplicity, reliability, and efficiency. There are several types of AC motors, including slip-ring motors, synchronous motors, and squirrel cage induction motors.

Slip-Ring Motor

A slip-ring motor, also known as a wound rotor motor, is a type of AC motor that consists of a rotor with windings connected to external resistors or a variable resistance. These external resistors are used to control the motor's speed and torque characteristics. Slip-ring motors are commonly used in applications that require high starting torque, such as large pumps, compressors, and mills.

Synchronous Motor

A synchronous motor is an AC motor in which the rotation of the rotor is synchronized with the frequency of the applied AC voltage. This type of motor has a rotor with permanent magnets or electromagnets that provide a constant magnetic field. Synchronous motors are known for their ability to maintain a constant speed even under varying loads. They are often used in applications that require precise speed control, such as electric clocks, conveyor systems, and machine tools.

Squirrel Cage Induction Motor

A squirrel cage induction motor is the most commonly used type of AC motor. It is simple, robust, and reliable, making it suitable for a wide range of applications. This motor consists of a stator with three-phase windings and a rotor with short-circuited conductors, resembling a squirrel cage. When the stator windings are energized, a rotating magnetic field is created, which induces currents in the rotor conductors. These currents interact with the magnetic field, causing the rotor to rotate. Squirrel cage induction motors are widely used in industrial and commercial applications, such as pumps, fans, compressors, and conveyor systems.

All Options are Correct

The correct answer to the question is option 'D' - All options are correct. This means that all of the mentioned motor types, namely slip-ring motors, synchronous motors, and squirrel cage induction motors, are AC motors. Each type has its specific characteristics and applications, and the choice of motor depends on the requirements of the particular application.