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In this study, the capacitance of capacitors connected in series with the auxiliary winding of a capacitor motor was changed by switching the firing angle of the triac, and ferrite magnetic wedges were inserted into the stator slots to reduce the flux density distortion in the air gap.

The characteristics of the capacitor motor under voltage control are highly applicable to home electric appliances. In this study, the supply voltage controlled by a triac has been applied to a split-phase capacitor motor. The capacitor motor usually produces an oscillative torque with a double supply frequency. When asymmetrical voltages controlled by the triacs are applied to the motor, the voltage and current behaviors are distorted. The authors have proposed a countermeasure of the insertion of ferrite magnetic wedges into the motor slot openings to smooth the flux density pulsation across the air gap. As a result, some significant relationships have been obtained.

The authors have inserted ferrite magnetic wedges into the stator slot openings of the capacitor motor to decrease the pulsation of flux density distribution in the air gap. As a result, the iron loss was reduced greatly to increase the motor efficiency and to improve other running characteristics.

The split-phase condenser motor is very useful for driving home electric appliances, but it has low efficiency. In other words, since the condenser motor is operated by two magnetic fields constituting positive phase and negative phase sequences, large electric power losses in light loads and oscillative torque are usually produced. In addition to this, the presence of the slot embedding electric conductors disturbs the flux density distribution in the air gap, producing tooth pulsation and higher harmonic losses. In this study, ferrite magnetic materials have been wedged into the stator slot openings of the condenser motor to smooth the pulsative distribution of the flux density in the air gap, and some experiments have been carried out to discuss the effect of the ferrite wedges on the motor characteristics with various running condenser capacities. As a result, the usefulness of the ferrite magnetic wedge has been verified.

Split-phase capacitor motors are commonly used to drive household electric appliances. The motor has some slots and teeth to embed electric conductors or coils. The presence of the slots and teeth induces the variation of magnetic reluctance through the magnetic circuit to introduce heavy pulsation of the air gap flux. Thus, the voltage, current and torque of the motor become oscillative to increase the electric power loss and finally to reduce the motor efficiency. First, the authors discuss the characteristics of a 3-phase cage-type induction motor in which the ferrite magnetic wedges have been installed into the stator slot openings of the motor to smooth the air gap flux pulsation and to decrease the electric power loss, resulting in improved motor efficiency. If the motor is driven by the voltage source in accordance with the loading condition, more economical operation will be achieved. In this study, a nonsinusoidal voltage controlled by the switching element of a triac has been applied to a capacitor motor with wedges of ferrite magnetic materials. This paper reports on the interesting results obtained.

Low-loss polarisation-maintaining fibres, with the zero dispersion wavelength shifted to 1.56 ?m, have been fabricated. A minimum transmission loss of 0.27 dB/km and crosstalk of ?22dB over a length of 4.1km, corresponding to h = 1.53 × 10-6m-1, are achieved at the same wavelength.