Numerical Analysis of Iron Integration in Dynamo Flux Pumps

Flux pumps (FPs) are contactless DC power supply systems used to energize superconducting magnets, with potential applications ranging from magnetic resonance imaging (MRI) to aerospace electric propulsion, nuclear fusion, and other applications. Among the various FP topologies, the dynamo FP belongs to the travelling-wave category, generating DC voltage through the rotation of permanent magnets (PM) facing high-temperature superconductor (HTS) tapes. One of the primary challenges of this system is the limited voltage level that can be generated, which results in a prolonged magnet charging time. A promising approach to optimize and enhance the dynamo FP configuration is the integration of a ferromagnetic material positioned behind the HTS tape with respect to the rotor. This addition strengthens the magnetic field acting on the HTS tape when the permanent magnets move in its vicinity, thus increasing the output voltage. This phenomenon has been confirmed by a few recent studies. However, it remains uncertain how this affects the losses induced in the HTS tape and, therefore, the overall energetic performance of the FP. This issue is critical because low efficiency may undermine the practical applicability of FPs. This paper extends the volume integral equation method, previously developed to model the dynamic behavior and to optimize the dynamo FP, to include the effect of a back iron material behind the HTS tape. The method is used to simulate and to compare the performance of different layouts of dynamo FPs, with and without back iron, to highlight its impact on system losses and efficiency. The results suggest that the magnetic circuit improves the dynamo's performance, accelerating the load magnet charging process and enhancing overall efficiency.