3D modeling of a superconducting dynamo-type flux pump

Abstract

High T_c superconducting (HTS) flux pumps are promising devices in order to inject large DC currents into the winding of superconducting machines or magnets in a contactless way. The superconducting dynamo, as a type of flux pump with simple structure and easy maintenance has become very popular during the recent years. Using the dynamos, employing troublesome brushes in HTS machines or bulky currents leads with high thermal losses will be no more required. The working mechanism of HTS dynamo in open-circuit mode and with transport current is complicated and not fully investigated yet, despite several explanations and models that have been proposed. In this work, we present the first 3D model of an HTS flux pump with good agreement with experiments. With taking advantage of this efficient 3D model, it is possible to pinpoint the process of generating voltage across the superconducting tape surface. This can be realized with analyzing the screening current and electric field distribution on the tape surface in several crucial time steps of traversing the magnet over the tape. This is important since the overcritical screening current has been shown to be the reason for flux pumping. We also analyzed the impact on the voltage generation of both in-tape components of the electric field and screening current, which in the former cases have not been studied before. In addition, we studied the performance of the dynamo in presence of fixed transport currents.