Reduced Order Models for Double-Cage Induction Motors

By neglecting the fast transients due to the starting cage, the conventional seventh-order model for a double-cage induction motor can be readily reduced to a fifth-order model with a structure which is different from the regular fifth-order model structure for a single-cage motor. To obtain stability in its digital simulation, however, winding flux-linkages rather than currents are used for the state variables. For studies where decaying alternating components of almost the line frequency in the active and reactive power flows are not relevant, the fifth-order model can be further simplified tQ a third-order one by neglecting the stator transients. The different reduced order models are validated by comparing their simulated responses with that of the full-order model for a full-voltage start-up as well as for the case when the motor is exposed to a temporary symmetrical fault at its terminals.