ABSTRACT
This chapter discusses three-phase induction motors and their performance characteristics. It then discusses motors of the fractional-horsepower class used for applications requiring low power output, small size, and reliability. Standard ratings for this class range from 120 to 1 hp. Motors rated for less than 120 hp are called subfractional-horsepower motors and are rated in millihorsepower and range from 1 to 35 mhp. These small motors provide power for all types of equipment in the home, office, and commercial installations. The majority are of the induction-motor type and operate from a single-phase supply. In the wound rotor motor, windings similar to those of the stator are employed with terminals connected to insulated slip rings mounted on the shaft. The rotor terminals are made available through carbon brushes bearing on the slip rings. The second type is called the squirrel-cage rotor, where the windings are simply conducting bars embedded in the rotor and short-circuited at each end by conducting end rings.
