Electromagnetic and Thermal Behavior of a Triple Redundant 9-Phase PMASynRM With Insulation Deterioration Fault

This article analyzes the electromagnetic and thermal behavior when insulation deteriorates, leading to short-circuit (SC) faults in a triple redundant 9-phase permanent magnet-assisted synchronous reluctance machine. It defines a critical insulation resistance at which the temperature in the faulted insulation region reaches the cut-through temperature of the insulation material and determines the minimum and maximum bounds of the critical resistance for all possible faulty insulation volumes by three-dimensional thermal analysis. It suggests insulation resistance thresholds for fault detection and mitigation action in order to prevent complete insulation failure with serious consequences. Moreover, an example is given to show that the insulation deterioration process may begin from large insulation resistance and is accelerated when the insulation material resistivity decreases with increase in temperature. Finally, tests on a prototype machine drive are performed to validate the predicted electromagnetic behavior under turn-to-turn insulation deterioration leading to SC faults.