Analytical method to calculate flux density in a superconducting (SC) direct-current (DC) wind generator

Compact, lightweight and large-scale generators are desired for offshore wind energy application. In order to meet the transportation and installation requirements, SC direct-drive wind generators are proposed as an attractive approach. The trend towards larger ratings and more offshore installations asks for new technical solutions. SC DC wind generators with alternative DC integration circuit to the grid could be an effective option due to fewer steps in energy conversion and high efficiency. In this paper, a general model for the SC DC generator with air-gap winding under no-load condition is proposed by magnetic fields analysis in 2D. In this model, the shape of the SC coil are described by the inner and outer radiuses of the SC coils, r_sci and r_sco, the half angles between two adjacent coil sides, α₁ and α₂. r_ri, r_ro, r_si, and r_so are the inner and outer radiuses of the rotor and stator, respectively. The cores of rotor and stator can be either made of ferromagnetic or nonmagnetic materials. The nonlinearity of the ferromagnetic materials are also taken into consideration.