Self-Limiting Control of Induction Machines

This paper presents a self-limiting control strategy for stator-limited induction machines. This controller gradually backs down the current once the temperature limit is reached and keeps the temperature fixed at the insulation class limit. In contrast to conventional protective devices, which would shut down the motor and not allow it to start in a warm state, the self-limiting controller avoids abrupt and premature system shutdown, and allows the system to operate at its thermal limit until the internal machine temperatures rise to their rated values. The results show that after reaching maximum hot-spot temperature the machine can be further overloaded as long as the end space is colder than rated.