Practical measurement of symmetrical component currents in induction motors

This paper details a procedure for deriving symmetrical current components based solely upon the magnitudes of the three phase currents in an induction motor system. The unbalance value is defined as the ratio of negative to positive sequence currents. It is difficult to calculate on a real time cycle using symmetrical components. However, it is important for a practical induction motor protection algorithm because the unbalance results in undue heating of the machine, particularly the rotor