Comparison of High Pole Number Ultra-Low Speed Generator Designs Using Slotted and Air-Gap Windings

This paper describes the simple design rules that can be used to design direct-drive brushless generators for an ocean wave device. This is a very low speed device so the pole number and diameter is very large. While these machines may be large, the pole pitch and axial length is low. The application is described and air-gap wound and slotted designs are developed and simulated using analytical and finite element analysis techniques. A 248-pole design with surface rotor magnets is developed. The machines use a substantial amount of permanent magnet material and a more compact version of the slotted machine is also developed.