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Accelerated aging tests have been carried on stator bars under simultaneous electrical, thermal and mechanical multi-stress conditions, using a simulated three-phase model stator. Over each thermal load cycle, the partial discharge activity has been found to be a strong function of temperature. Tests at twice rated electrical stress did not result in any bar specimen failures up to a total of 1500 load cycles. However, when the three phase load current was increased above its rated value, current-limited type failures were observed to occur below 1000 load cycles, thereby indicating a marked influence of thermal and mechanical stresses associated with the elevated three phase load current.