Identification and Compensation of the Rotor Temperature of AC Drives by an Observer

The magnetic flux of induction motors fed by current-source or current-controlled voltage-source inverters is normally controlled indirectly and considerably influenced by rotor temperature. Since the additional installation of temperature sensors does not agree with the intention of a sturdy drive, indirect detection using only easily measurable quantities is desired. On-line observation of the machine by a model implemented in a microcomputer allows closed-loop estimation of the disturbing temperature. Requirements on the accuracy of the model and the measured data are discussed. The feedback from the estimation program to the analog inverter control including experimental results is demonstrated.