Effects of ferrite magnetic wedge on characteristics of capacitor motor controlled by triac

The flux density distribution in the air gap on revolving electric machines is distorted by the presence of slots and teeth to produce rotor pole face eddy current and stator tooth pulsation losses, resulting in the reduction of motor efficiency. When the asymmetric voltage controlled by switching devices such as a triac is applied to the motor, the voltage and current also pulsate to increase power losses. In the present study, ferrite magnetic wedges have been inserted into the stator slot openings of the capacitor motor and some experiments under the triac control have been carried out. It is found that the pulsation of the flux density distribution in the air gap is decreased by wedging the ferrite materials to increase the apparent magnetic permeability. This resulted in decreasing the motor power losses and improving the motor running characteristics