Modeling and measurement of airgap harmonics of single-phase induction motors

The air-gap harmonic frequencies of a single-phase squirrel-cage induction motor are studied analytically using the permeance method. This approach delivers detailed information about the air-gap harmonic frequencies, corresponding pole pairs, and the originating mechanisms, such as excitation, slotting, or saturation. In order to verify this analysis, experimental measurements are carried out on a 1/3-hp single-phase induction machine. The harmonic frequencies and nature of the field waveforms are studied under different operating conditions. Excellent correlation is found between theoretical and experimental results.