Direct-drive turbo alternators

The author reviews economical and practical aspects of alternators operating at gas turbine speed in the size range from 100 kW to 1000 kW. Nonconventional alternators, such as flux-switched inductor Naydyne, external rotor permanent magnet, and switched reluctance alternators, are discussed. Electronic frequency reduction units for these alternators, such as cyclo-converters, stepped wave inverters, constant voltage pulse-width modulated inverters, or constant-current pulse-width modulated inverters, are presented. It is found that the evolution of electronic devices in this power range tends to support replacing mechanical gear reduction with a semiconductor frequency changer. An overview of these concepts is presented along with a description of a hypothetical package.<>