Revolving-Field Analysis of a Shaded-Pole Motor

The revolving-field theory as applied to singlephase induction motors is extended to develop a concise, yet comprehensive, theory for shaded-pole motors with single shading coil. The analysis can, however, be easily extended for motors with multiple shading coils. The novel features of this development are that it provides means to properly account for the magnetic saturation, space harmonics and the core loss. The analysis is based upon the concept that a winding can be simulated by a pair of mutually perpendicular windings. Based upon this concept and the revolving-field theory, an equivalent circuit for a shaded-pole motor is proposed. Performance equations are then presented and a step by step procedure is outlined to effectively utilize these equations. The accuracy of the development was confirmed by actual measurements on shaded pole motors with various horsepower ratings. To show that the present development yields better correlation, comparisons between actual test results and computed data using the present model, as well as other existing models are also given.