Publisher Summary This chapter discusses the commonly used general-purpose alternating current motors. Electric motors are the most common drivers for the majority of pumps, compressors, agitators, and similar equipment in the process industries. Process engineers should obtain the assistance of a qualified electrical engineer before completing motor specifications for the wide variety of equipment applications and respective power sources. Variations in required speed or speed increase or decrease from the driver may be handled by gear boxes, belt or chain drive, magnetic drive, magnetic or fluid couplings, or variable-speed motors. The belt drive must be properly grounded. In explosive or hazardous atmospheres, belts are not recommended, but if used, they must be of the anti-sparking design with special brushes to ensure the grounding of static charges. The chapter reveals that torque is the turning effort developed by the motor or the resistance to turning exerted by the load. Usually torque is expressed in ft-lb; however, the usual expression is as a percentage of the full load torque. Synchronous motors usually offer several types of torque. Starting or breakaway (called locked rotor) torque is developed at the instant of starting. The torque requirements of the driven equipment determine the torque specifications of the motor from initial start to shutdown.