Statistical evaluation of accelerated voltage endurance tests on mica insulation for rotating electrical machines

Accelerated voltage endurance testing at elevated test frequencies has been carried out. Testing of discrete populations at 50 and 500 Hz and identical field strength values yields acceleration factors between 3.4 and 22.2. However, if all populations with varying field strength values in the range from 5 to 24 kV/mm are combined and the theoretical frequency conversion factor of 10 is applied, the spread of the individual values is no greater than that obtained at a single test frequency. Each individual endurance curve lies within a 95% confidence limit of the other curves.>