Auxiliary Phase Design for Capacitor Start Motors

Abstract

A procedure is described for calculation of an auxiliary phase for a single-phase capacitor start motor. The size of wire, the number of turns, and the size of capacitor are determined to meet five restraints. These restraints are: required locked rotor torque, maximum allowable capacitor volts, maximum allowable locked rotor current, greatest current density in the auxiliary winding, and largest slot fullness that is permitted. A trial winding is calculated using estimated number of turns, a trial wire size, and a trial capacitor. The characteristic impedances are determined as a function of winding ratio, wire size, and capacitor size. For each wire size and capacitor, an auxiliary winding is determined which will meet the restraints if it is possible. The method is arranged to facilitate digital computer programming. The logical flow is such that the program will arrive at the best auxiliary or determine that no satisfactory design exists.