Implementation of fractional slot concentrated winding technique to large salient-pole synchronous generators & development with permanent magnets

This paper presents an implementation of the fractional slot concentrated winding (FSCW) technique into large salient-pole synchronous generators (SPSGs) and the development of the generators by using additional permanent magnets (PMs). Compared to conventional synchronous generators, the FSCW technique makes it possible to achieve lighter, cheaper and higher-efficiency generators with a simpler structure. To overcome saturation of the rotor pole-body problem well known in the SPSGs, the designed FSCW SPSG has been developed by inserting PMs between the rotor-pole shoes. The insertion of PMs between rotor poles increases the generator power output while reducing magnetic saturation in the rotor pole body. Using these features of the PMs, more compact generators can be designed while keeping the same output parameters. In order to achieve these objectives, the FSCW and PM-FSCW SPSGs are designed by using finite element simulation software (MAXWELL^®). Furthermore, designed machines are compared with conventional SPSGs in order to realize the degree of the improvement. The machines are modeled not only by using MAXWELL^® but also by using a simple nonlinear magnetic circuit to describe the effects of PMs. Simple theoretical expressions and detailed comparisons of performance characteristics of the designed machines are presented.