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

Revolving electric motors are generally installed with slots and teeth (iron portion between slots) to embed electric conductors. The presence of the slots and the teeth introduces the variation of magnetic reluctances through the magnetic circuit to produce pulsation of the flux distribution in the air gap. As the result, the voltage, current and torque of the motor becomes oscillative to increase electric power losses and at last to decrease motor efficiency. The authors have found that the rectangular hysteresis loop of ferrite materials as the magnetic wedge into motor slot openings are very effective to reduce the pulsation of flux density distribution in the air gap. If the motor is drived in accordance with the loaded conditions, more economical operation is expected. In this study, the capacitor motor has been controlled by the triac. However the voltage wave controlled by the triac is an asymmetric sinusoidal wave and so the flus density distribution in the air gap is disturbed to increase motor power losses and to produce oscillative torque. Thus the ferrite materials were wedged into the slot openings of the capacitor motor controlled by the triac and some experimental discussions have been developed.