Description of a thermal cycling test set-up for large turbine generator armature coils

The IEEE-Electric Machinery Committee, Materials Subcommittee has established working group P1310 to develop a simplified standard test procedure for thermal cycling of unrestrained coils. This paper describes the authors´ work aimed at creating a test set-up to meet the working groups´ draft standard and to provide useful data for comparing insulation systems. Methods of heating, temperature control, and temperature measurement are all critical to establishing a thermal cyclic test procedure that closely models generator operating conditions, and is repeatable. Internal heating is preferred since it replicates actual operating conditions. Various methods of using current for internal heating are available. In this case multiple strands are connected in series and normal strand current levels are driven through the strands. The characteristics of this feature are discussed. The results of several temperature measurement methods are discussed along with the method of temperature control. Temperature control is achieved by cycling current off and on based on the measurement of internal copper temperature