Thermal endurance testing of rotor turn insulating materials

The ongoing evaluation of material properties, including thermal performance, is part of the continuing evolution of insulation system development. In large strip-wound rotors, a coated aramid paper is used to bond the coil turns together and provide turn-to-turn insulation. Experience has shown that the thermal performance of the system is limited by the capability of the bonding material. This paper describes a program to verify the thermal capability of a strip-wound rotor insulation system. Several candidate materials were subjected to initial screening tests, from which two were selected for thermal ageing tests. Accelerated thermal ageing tests were performed in accordance with IEEE Std 98-2002 and IEC 60216-1 to compare the thermal performance of the materials. This paper describes the results of the thermal ageing tests and the failure modes encountered