A thermal cycling type test for generator stator winding insulation

A test has been designed and implemented which cycles the temperature between 40°C and 150°C in about 80 min by the use of circulating currents and cooling air. The test has been successfully used to evaluate the relative performance of similar stator bars made by three different manufacturers. The thermal cycling test was able to duplicate the insulation delamination process and presumably those insulation systems which performed well in the thermal cycling test could last longer in service. In addition to being used for pumped-storage generators, the thermal cycling test may be useful to evaluate the insulation system in combustion turbine generators