An Electromagnetic Design of a Fully Superconducting Generator for Wind Application

Abstract

A fully superconducting wind generator employs superconductors in stator and rotor to enable high torque density and low weight, that is, enable an ultra-light electric machine for wind application. However, the level of the AC loss of the stator armature coils is a critical issue, which lacks investigations in the design of the fully superconducting generators. In this paper, an in-house model was developed to analyze the potential of a fully superconducting generator by integrating the electromagnetic design with the AC loss estimation. The electromagnetic model was made through analytical equations, which take into consideration the geometry, the magnetic properties of iron, and the nonlinear E–J constitutive law of superconductors. Since the permeability of iron materials and the critical current of the superconductors depend on the magnetic field, an iteration process was proposed to find their operating points for every electromagnetic design. The AC loss estimation was carried out through finite element software based on the T–A formulation of Maxwell’s equations instead of analytical equations, due to the complexity of magnetic fields, currents and rotation. The results demonstrate that the design approach is viable and efficient, and is therefore useful for the preliminary design of the generator. In addition, it is found that smaller tape width, larger distance between the superconducting coils in the same slot, smaller coil number in one slot and lower working temperature can reduce the AC loss of the stator coils, but the reduction of the AC loss needs careful design to achieve an optimum solution.

FEM-Circuit co-simulation of superconducting synchronous wind generators connected to a DC network using the homogenized J–A formulation of the Maxwell equations

“…During the pre-design phase, the critical current (I c ) of the HTS tape inside the winding is evaluated using the load-line method [54,55]. The maximum value of the norm of the magnetic flux density B (the norm denoted as B) is evaluated over the stack of HTS tapes as a function of the current in the rotor.…”

Superconducting Electric Power Systems: R&D Advancements

“…In Ref. [19], the authors focus on the design of a 10 MW, 10 rpm fully superconducting direct-drive wind generator, with special attention to the AC losses of the SC stator windings. Considering separate cryostats for the stator and rotor coils, the generator geometry is optimised to achieve 10 MW while maximising the output power per meter (volumespecific power), Figure 7.…”

“…This editorial paper presents and discusses the R&D and tests of superconducting technologies that aim to demonstrate the performance of this technology in electric power systems for more efficient use of energy. The editorial covers: [16][17][18][19][20].…”

Numerical modelling of HTS tapes under arbitrary external field and transport current via integral method: review and application to electrical machines *

“…Later, instead of the two-stage method, fully coupled models were developed in which the full machine with superconductor tapes was simulated in one model, e.g. by the H-A formulation [31,32] and the T-A formulation [33][34][35][36][37][38][39][40][41]. The H-A and the T-A formulations have been compared [39,41,42].…”