A half-wave superconducting transformer-rectifier flux pump using J _c(B) switches

Abstract

High temperature superconducting (HTS) flux pumps can generate ultra-high currents (>1 kA) without the requirement for thermally inefficient room temperature current leads. Ultra-high currents enable physically smaller magnets with significantly less inductance unlocking new design opportunities. However, limited by intrinsically low electrical power efficiencies, existing HTS flux pumps cannot output high voltage or high power. In this work, we design, devise, and experimentally verify a transformer–rectifier type HTS flux pump using Jc(B) switching. We show that the rectification can be achieved by exploiting the HTS E-J relation with the application of DC magnetic fields. A quasi-persistent current of 54.5 A has been achieved at 77 K only limited by the load coil critical current. In addition, the electrical power efficiencies of both half-wave and full-wave flux pump are derived. We illustrate that the fundamental Jc(B) mechanism provides significantly higher efficiency than existing HTS flux pumps. This advancement will overthrow the common knowledge that HTS flux pumps could only be used for maintaining rather than fast ramping magnetic fields.

Miniaturized HTS linear flux pump with a charging capability of 120 A

“…A flux pump usually refers to a device that eliminates bulky current leads and indirectly injects current into the superconducting coil, which is a promising power source for HTS coils [9][10][11][12]. Recently, HTS flux pumps have received a lot of attention, such as transformer-rectifier flux pumps [13][14][15][16][17] and traveling wave flux pumps [18]. At present, there are several types of travelling wave flux pumps, mainly including thermally actuated flux pumps [19][20][21], HTS dynamo flux pumps [22][23][24][25][26][27], linear-motor type flux pumps [28][29][30][31], pulsetype flux pumps [32,33] and linear flux pumps [34,35].…”

Effective circuit modelling and experimental realization of an ultra-compact self-rectifier flux pump

“…Rectification is achieved by driving current larger than the critical current, I c , through part of the superconducting circuit (the 'bridge') for part of the input waveform cycle. This 'self-rectification' method was originally described for hightemperature superconductors by Vysotsky et al [8], and can be compared with FPs that employ various active switching mechanisms to vary the I c of the bridge [1,[9][10][11][12]. Selfrectifying FPs are capable of delivering large currents at modest voltages [3] without a requirement for direct electrical and thermal connection between the superconducting load and an ambient temperature power supply, which can lower the overall heat load on the cryogenic system when compared with a conventional power supply [1,13,14].…”

MOSFET-based HTS flux pump

“…With the last mentioned method, the highest current of 700 A was achieved in 2018 [15]. The transformer-rectifier flux pumps can be divided into categories based on the method of switching, which are dynamic resistance switches [16,17], overcurrent switches [18,19] and other new types of switches [20,21]. The first successful demonstration of an HTS flux pump based on metal-oxide-semiconductor field-effect transistors (MOSFETs) took place in 2005 [22].…”