Abstract: An electrical insulation system for the turns of multiturn stator coils, found in the windings of high voltage hydroelectric generators and other dynamoelectric machines, having only one of the outer strands of each turn insulated with mica with the remaining strands insulated with DACRON-glass. This construction, while offering adequate turn to turn dielectric strength in machines where the turn to turn voltages are moderate, allows the coils to be manufactured at a lower cost and permits the use of strands of significantly larger copper cross-section area.

Abstract: An insulation system for the turns of a multiturn coil in a high voltage electrical generator or motor having the outer strands of each turn insulated with a high dielectric strength material such as mica and having the inner strands insulated with a low dielectric strength material such as double dacron glass (DDG) or single dacron glass (SDG). The outer mica insulated strands of the turn are smaller in width than the inner DDG or SDG insulated strands in order to accommodate the differences in thickness between the mica, DDG, SDG or other materials used for strand insulation and in order to create a higher overall dielectric strength in the ground insulation of the coils. The outer mica insulated strands of the turn are different in thickness from the inner DDG or SDG insulated strands in order to minimize the Eddy and Circulating Current Losses of the winding and in order to accommodate the differences between the mechanical strengths of the mica and the DDG/SDG tapes.