AC machines, or alternating current machines, are electrical devices that convert electrical energy into mechanical energy or vice versa. They operate using alternating current, which changes direction periodically. The two main types of AC machines are AC motors, which convert electrical energy into mechanical motion, and AC generators, which convert mechanical energy into electrical energy. These machines are widely used in various applications, from household appliances to industrial equipment. Induction motors and synchronous motors are common types of AC motors, while synchronous generators are often used in power plants. Their efficiency and reliability make them essential in modern electrical systems.