Design analysis of capacitor-start, capacitor-run single-phase induction motors

Capacitor-start, capacitor-run single-phase induction motors are analyzed by means of rotating field theory using the method of symmetrical components. The approach is based on the current ratio γ, relating the backward and forward rotating components of the main and auxiliary-phase winding currents. Since the losses of such a machine are greatly dependent upon the elliptic shape of the rotating field, such an analysis in terms of γ will be of value for any efficiency optimization. The dependency of the efficiency on the run capacitor´s capacitance is investigated. Since the parameters of the equivalent circuit are slip, temperature, and saturation-dependent, a computer program is developed which determines in an iterative manner the performance of such machines. A large number of tests are performed for a 4-pole, 2 Hp, 115/230 V motor. The experimental data corroborate the calculated characteristics which show that the maximum efficiency is reached for a nonzero but small value of γ