Synchronous rotor thermal model based on stator current modulation
Starting synchronous motors connected to high-inertia loads often leads to starting times greater than the synchronous motor locked rotor time. This compromises thermal algorithm capabilities to provide adequate rotor thermal protection under stall and slow acceleration conditions. This study presents a novel slip-dependent thermal model which obtains a slip estimated using stator current modulation caused by rotor saliencies. The proposed algorithm is validated using an OpenModelica model and its performance is compared against the conventional slip-independent thermal model. Finally, the algorithm is implemented in a protective relay and field tested on a 28820HP motor driving a high-inertia gas injection compressor at a natural gas liquids facility.