HTS Flux Pump Charging an HTS Coil: Experiment and Modeling

An HTS flux pump is an effective device to compensate the field decay in HTS magnets running in persistent mode. This paper contains updates to the model for the travelling wave HTS electromagnetic flux pump, in which the magnetization system is modelled as an L-R circuit. In this paper we consider the various sources of resistance. There are three components, joint resistance, resistance of superconductor and dynamic resistance. Joint resistance is treated as a constant. The superconducting resistance is derived from the E-J model and finally the dynamic resistance is a function of applied field strength and frequency. In addition the model includes the electromotive force which is a function of the applied field, frequency and surface area of the tape. This is a calculated value based on the φ model we built. In order to test the model, a series of experiments were performed in which an HTS coil was actuated using our flux pump. The flux pump test rig was made from 4-pair rectangular copper solenoids with laminated iron cores, which were fixed on the supporting iron frame. This rig was used to magnetize a double layer HTS racetrack coil at 77 K. The induced current in superconducting coil can reach more than 90% of critical current. Our model was found to be a good fit to the experimental data.