Magnetic wedges in a steam-resistant electrical machine insulation system

The overall system efficiency of small turbogenerators and compressors can be significantly increased by using high-speed electrical machines. These machines enable a high level of system integration and compactness. In the studied turbogenerator application the turbine leakage steam is in direct contact with the electrical machine and therefore all the components of the machine insulation system, including magnetic wedges, must tolerate the process environment. The magnetic wedges improve the electrical machine performance. The effects of the superheated steam on several wedge materials with different coatings were studied by experimental accelerated aging tests. A test installation was developed to test the simultaneous influence of the temperature and moisture on the wedge aging. According to the data obtained from the visual inspection, microscope, Fourier Transform Infrared spectrum analysis, and dimension measurement analyses, different wedges absorb various amounts of water in a steam atmosphere. The effects of the coating layer damage during the wedge installation into the electrical machine, are observed.