The zero-sequence parameters and performance of three-phase induction motors

The authors have already demonstrated1 that zero-sequence currents can produce a finite torque in a 3-phase induction motor, and that it is the predominant component torque in certain cases of asymmetrical connection. The present paper shows, for the first time, how the relevant parameters for zero-sequence operation may be determined from certain test results, and how they may be utilized to predict the performance of the machine when zero-sequence voltages only are applied to the primary winding. It is suggested that the considerable torque available may find useful application in providing a speed reduction of 67% for brief periods of operation.