ABSTRACT
Electric motors convert electrical power into mechanical force, which is used to produce rotation or torque. Motors include two concentric, cylindrical, laminatediron cores separated by an air gap to carry magnetic flux, and two sets of windings wound or embedded in slots in iron cores with either or both excited by direct current (DC) or alternating current (AC). Inactive motor elements include the frame, end bells, and bearings. Motor speed is a function of applied power frequency. Speed control can be obtained by varying this power frequency. Load-speed and load-torque requirements are tied to the torque-speed characteristics. Torque developed at the motor shaft is proportional to rotor current and the square of the terminal voltage. Motor type classification is dependent upon how the stator or rotor windings are excited. The three general motor classes are induction alternating current, synchronous alternating current, and direct current. AC motors can be used effectively for the majority of motor applications, except when very high starting torques are required.
