The design optimisation of a split phase fan motor with triac voltage (speed) control

Significant improvements in the performance of the triac voltage control of split-phase fan motors can be achieved by increasing the rotor resistance and winding ratio. These improvements include a reduction in the maximum main winding current and an increase in the speed stability throughout the control range. The analysis of the motor performance with triac control of the main winding voltage only, is based on independent consideration of the functional (supply) frequency and harmonic content of the applied chopped sinusoidal voltage. Excellent agreement with measured results is obtained and comparision with variac control can be made directly.