In this research, six hybridmachine topologies, utilizing both a field winding and permanent magnets, are investigated for fixed-speed dc generation. The hybrids are compared with the wound-rotor and permanent magnet synchronous machines. To this end, analytical system models are utilized to predict machine-rectifier behavior. A general approach used to develop themachine models is discussed; the rectifier and filter models are also presented. The system models are used in a multi-objective design process to establish the tradeoff between overall mass and loss. Detailed losses, geometries, and rectifier waveforms obtained from the design studies are presented for four of the machine types.