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. Common types of AC machines include AC motors and AC generators, which are widely used in various applications, from household appliances to industrial equipment. AC motors are designed to drive mechanical loads, while AC generators, also known as alternators, produce electricity. These machines are essential in power generation and distribution systems, as they help convert energy from sources like wind turbines and hydroelectric plants into usable electrical power.