A General Method of Analysis of Three-Phase Induction Motors with Asymmetrical Primary Connections

It is demonstrated that a systematic application of the theory of symmetrical components to the phase quantities of a symmetrically-wound induction motor provides a general method of analysis which can be used to predetermine the performance characteristics of the motor for any form of asymmetrical primary connection. Among the particular forms of asymmetry considered in some detail are abnormal connection of the primary phases and the insertion of asymmetrical line impedances or auto-transformers. It is noted that discrepancies in published work on the subject are due to ignoring the presence, or incorrectly assessing the effect, of the zero-sequence system; this system is therefore given special attention. Experimental results confirm the validity of the general method.