A Comparative Study on Design Method of Stator Winding for Direct-drive Shaft Generator

Marine environment protection committee of the international maritime organization chose an energy efficiency design index to regulate carbon dioxide emission of new ships in 2011. Various methods to reduce this index have been examined and applied to ships; one is a shaft generator installed with a main engine that provides additional power to electrical loads instead of one or two diesel engine(s). In this paper, the shaft generator combined directly with the two-stroke main engine is introduced. Models of integer-slot and fractional-slot winding are designed by finite element analysis and equivalent magnetic circuit approach. Harmonics in back electromagnetic force, torque pulsations, iron core losses, and radial magnetic forces are investigated and compared for each model. The test result of a 1,200kW prototype on the no-load operation is compared with the result of finite element analysis.