Abstract
High temperature superconducting (HTS) rotatory flux pump, or so called HTS dynamo, can output none-zero time-averaged DC voltage and charge the rest of the circuit if a closed loop has been formed. This type of flux pump is often employed together with HTS coils, where the HTS coils can potentially work in persistent current mode, and act like electromagnets with considerable magnetic field, having wide range of applications in industry. The output characteristics of HTS rotary flux pumps have been extensively explored through experiments and finite element method (FEM) simulations, yet the work on constructing statistical models as an alternative approach to capture key characteristics has not been studied and published. A 2D FEM program has been used to model the HTS rotatory flux pumps and evaluate the effects of different factors upon the output voltage through parameter sweeping and analysis of variance. Typical design considerations, including operation frequency, air gap, HTS tape width and remanent flux density have been investigated, in particular the bilateral effect of HTS tape width has been explained by looking at the averaged integration of the electric field over the tape. Based on the data obtained from various simulations, regression analysis has been conducted through a collection of machine learning methods and demonstrated that the output voltage of a rotary flux pump can be obtained promptly with satisfactory accuracy via Gaussian process regression, aiming to provide a novel approach for future research and powerful design tool for industrial applications using HTS rotary flux pump devices.
Highlights
As stated in [25, 44], the open circuit voltage of High temperature superconducting (HTS) dynamo originates from the actions of circulating current within the tape, which can be equivalently reflected by the voltage division on the backward and forward eddy current regions, and it is the electric field generated on the forward eddy current region that essentially forms the DC output voltage
It was pointed out that the Jc(B) dependence tends to increase the dynamic resistance for the tape region beneath the permanent magnet, where the forward eddy current flows, and elimination of such dependence, e.g. assume constant Jc, will cause less of the conserved EMF to be distributed to the forward eddy current region and result in a smaller open circuit voltage, from which we demonstrated the importance of considering field dependence of Jc in such models
Based on this numerical model, a comprehensive sensitivity analysis was conducted for the open circuit voltage Voc versus the operating frequency f, air gap g, SC tape width Ws and remanent flux density of the permanent magnet Br
Summary
In order to enable the advance of a variety of applications in the future [1,2,3,4,5], such as wind turbines, all electric aircraft propulsion systems and energy storage devices, the clear trend in. Flux pumping effects in HTS rotary flux pumps have been investigated experimentally for different influential design parameters, such as the air-gap distance [18], the operating frequency [19], the width of the stator wire [20] and the geometry of the magnet [21], and typical curves for output characteristics have been obtained. Both qualitative and quantitative analysis [22,23,24,25,26,27,28,29] have been done previously for the output characteristics of HTS dynamo, but little attention has been paid to integrate all design parameters together and derive a model that can capture the output characteristics in a fast and accurate manner. The magnetic vector potential A is introduced to link the distribution of sheet current density in the superconductors, and comes to the A-formulation part:
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