The starting of single-phase induction motors

The object of this paper is to analyse some of the various starting arrangements used with single-phase induction motors. As is well known, these machines have inherently no torque at standstill but require special devices to produce this torque by altering the motors during the starting period into unsymmetrical polyphase induction motors. It is proposed to deal only with electric starting devices, which have found an extensive commercial application for motors from about 1 to 100 h. p. Mechanical means of bringing single-phase induction motors such as pony motors, etc., up to speed, will not be considered in this paper. Inductive devices of either the external or the internal type are practically confined in their application to fractional horse-power machines and therefore will only be mentioned here for the sake of completeness.