Novel model of stator design to reduce the mass of superconducting generators

Abstract

High temperature superconductors (HTS), with much higher current density than conventional copper wires, make it feasible to develop very powerful and compact power generators. Thus, they are considered as one promising solution for large (10+ MW) direct-drive offshore wind turbines due to their low tower head mass. However, most HTS generator designs are based on a radial topology, which requires an excessive amount of HTS material and suffers from cooling and reliability issues. Axial flux machines on the other hard offer higher torque/volume ratios than the radial machines, which makes them an attractive option where space and transportation becomes an issue. However, their disadvantage is heavy structural mass. In this paper a novel stator design is introduced for HTS axial flux machines which enables a reduction in their structural mass. The stator is for the first time designed with a 45 ° angle that deviates the air gap closing forces into the vertical direction reducing the axial forces. The reduced axial forces improve the structural stability and consequently simplify their structural design. The novel methodology was then validated through an existing design of the HTS axial flux machine achieving a ~10% mass reduction from 126 tonnes down to 115 tonnes. In addition, the air gap flux density increases due to the new claw pole shapes improving its power density from 53.19 W/kg to 61.90 W/kg. It is expected that the HTS axial flux machines designed with the new methodology offer a competitive advantage over other proposed superconducting generator designs in terms of cost, reliability and power density.

A critical review on wireless charging for electric vehicles

“…Even though HTS is more expensive than copper, it has already been used as coil material, e.g. for power generators of wind turbines [113], [114] and fault current limiters [115], [116]. But HTS is not as prevalent in WPT.…”

A modular and cost‐effective high‐temperature superconducting generator for large direct‐drive wind turbines

“…In order to explore the benefits of the added inner stator, a reluctance network of the double claw pole machine was developed in MATLAB [17,18]. The reluctance network is shown in Figure 5.…”

“…A Newton–Raphson type algorithm is used to solve the non‐linear flux equations. A detailed explanation for the algorithm that was used can be found in [17]. In addition to the reluctance network model, 3D finite element analysis using the simulation software MagNet was performed.…”

“…It is a cobalt iron alloy, which is relatively expensive in comparison to other electrical steels. However, it allows high air gap flux densities without using an excess amount of superconducting tape as compared to air-cored superconducting generator designs [17]. In addition, Vacoflux50 can be manufactured in laminations.…”

Modular and stackable power generators for efficient renewable power generation

“…The field winding can be wound into separate loops with separate cryostats, hence even if one of the field windings has a fault the generator can continue to work under partial load. Detailed discussions on the generator's basic electromagnetic characteristics, such as electromotive force (EMF) and torque, can be found in [5,18]. Table 1 provides a general summary of the double claw pole generator design such as dimensions and electrical characteristics.…”