Limitations of the DC Output Voltage From HTS Flux Pumps

The use of High-temperature superconducting (HTS) flux pumps has emerged as a promising approach for energizing HTS magnets. Compared to conventional power supplies, HTS flux pumps enable the wireless injection of a substantial dc current into a closed HTS magnet, allowing the magnets to operate in a persistent current mode. There are a lot of advantages to energize the HTS magnets in this manner. First of all, it avoids sophisticated power supplies and heavy current leads. Secondly, excessive cryogenic losses caused by thick warm-to-cold current leads can be reduced. Additional benefits include cost-effectiveness, reduced energy consumption, and a compact form factor. The most important parameter to evaluate the performance of the flux pump is its dc output voltage, which determines the charging capability. In this paper, we study both instantaneous and time-averaged dc output voltage for two most popular flux pumps - transformer-rectifier flux pump (TRFP) and high-Tc superconducting dynamo by a finite-element method model. Moreover, their working principles, structures and operation strategies are discussed. This work reveals characteristics and limitations of two flux pumps and is indicative for designing a high performance HTS flux pump for the specific application.