Decreasing the Tooth Pulsation Loss by Use of Ferrite Magnetic Wedges in a Capacitor Motor

A rotating machine with a stator slot has an energy loss caused by pulsation of the magnetic flux density distribution in the air-gap part. This loss is called the tooth pulsation loss. The purpose of this paper is to discuss the mechanism of a decrease in the tooth pulsation loss achieved by the use of ferrite magnetic wedges. We chose a capacitor motor as an object of analysis. We propose a method for estimating the tooth pulsation loss from the induced voltage of a virtual coil placed on the rotor surface. By analyzing the induced voltage of a virtual coil, using harmonic analysis, we clarified the relation of the tooth pulsation loss to the number of stator slots and the magnetic characteristics of the wedge materials.