The use of auxiliary impedances in the single-phase operation of polyphase induction motors

Recent literature indicates a considerable interest in the subject of single-phase induction motors which use split-phase starting. In the available motors condensers are often used as auxiliary impedances in the starting circuit and may also be used in the running circuit. Much of the existing literature on these machines deals with the condenser required and the torque developed. For the purposes of this analysis ideal conditions of balancing will be assumed. If the auxiliary impedances are properly chosen the motor windings will be subjected to balanced polyphase voltages. Under these conditions the motor will operate as a polyphase motor and the analysis may be carried out using standard polyphase motor theory and a-c circuit theory. The first machines analyzed will be of symmetrical two- and three-phase design. Following this, motors having unsymmetrical windings will be considered. Some observations on the related subjects of motor size and motor rating will also be included.