Presentation Information
[APP1-17]Inductance behaviour of a hybrid copper-HTS transformer at different temperatures and a novel liquid cryogen level sensor
*Adam C Francis1, Michael Southon1, Ryan Galloway1, Andres E Pantoja1, Rodney A Badcock1,2,3 (1. Robinson Research Institute (New Zealand), 2. OpenStar Technologies (New Zealand), 3. Dodd Walls Centre (New Zealand))
Keywords:
Liquid Cryogen Level Sensor,Superconducting Transformer,Superconducting Transition Temperature,Complex Impedance,Flux Pump,Cryogenic Electronics
Transformer rectifier flux pumps are devices that inject a DC current into a HTS coil in a cyclic manner [1]. To design a transformer rectifier flux pump effectively the electrical, magnetic and thermal behaviour of all parts of the device need to be well understood [2, 3]. The power that is delivered into a transformer rectifier circuit is defied by the transformer and the power supplies attached to the primary of that circuit. All transformer rectifier flux pumps use a transformer with many turns on the primary side and few turn on the secondary side, resulting is a step down in voltage and a step up in current. It is not uncommon for transformer rectifier flux pumps to have a turns ratio of 100:1 or more [4, 5]. During the design process of a total system, inclusive of driving power supplies, the impedance of the circuit must be determined from the perspective of the power supply attached to the transformer primary windings.
In this presentation the findings from a manuscript recently submitted for publication will be presented. This work is focused on the complex impedance behaviour of a hybrid copper-superconductor transformer. The complex impedance across the copper primary winding of a transformer with a superconducting secondary was measured at different temperatures. These results were compared to resistance data taken at the SuperCurrent Facility at Robinson Research Institute. The temperature range of the conduction cooled experiment spanned the transition temperature of the closed circuit superconducting secondary. These measurements showed a change of the inductance across the secondary of roughly half an order of magnitude over the superconducting transition of the secondary windings. This is key piece of information to consider when designing a total flux pump system which includes the driving power supplies, as changes in impedance of the circuit affect total flux pump performance and control.
As the change in the primary inductance was repeatable, the experimental apparatus was adapted to be a novel, compact and low power liquid cryogen level sensor requiring only 19 mA of AC current. This sensor was successfully demonstrated as a level sensor for liquid nitrogen at atmospheric pressure. This simple approach to liquid cryogen level sensing in combination with different superconducting materials can be used to monitor the fill levels of many cryogenic liquids or cryogen temperatures altered by pressure by matching the superconducting secondary material transition temperature to the liquid cryogen in question.
References
1. J. Geng, et al., High-Tc superconducting transformer-rectifiers: principle, realization, and applications. SUST, 2025. 38(4): p. 043001.
2. A.C. Francis, et al., Electrical, magnetic and thermal circuit modelling of a superconducting half-wave transformer rectifier flux pump using Simulink. Superconductivity, 2023. 7: p. 100053.
3. A.C. Francis, et al., Jc(B) transformer rectifier flux pump optimisation via simulation. SUST, 2024. 37(12): p. 125005.
4. J.H.P. Rice, et al., Report On Progress Towards a 10 kA Transformer-Rectifier Flux Pump. IEEE TAS, 2024: p. 1-7.
5. Z. Wen et al., High Temperature Superconducting Flux Pumps for Contactless Energization. Crystals, 2022. 12(6): p. 766.
In this presentation the findings from a manuscript recently submitted for publication will be presented. This work is focused on the complex impedance behaviour of a hybrid copper-superconductor transformer. The complex impedance across the copper primary winding of a transformer with a superconducting secondary was measured at different temperatures. These results were compared to resistance data taken at the SuperCurrent Facility at Robinson Research Institute. The temperature range of the conduction cooled experiment spanned the transition temperature of the closed circuit superconducting secondary. These measurements showed a change of the inductance across the secondary of roughly half an order of magnitude over the superconducting transition of the secondary windings. This is key piece of information to consider when designing a total flux pump system which includes the driving power supplies, as changes in impedance of the circuit affect total flux pump performance and control.
As the change in the primary inductance was repeatable, the experimental apparatus was adapted to be a novel, compact and low power liquid cryogen level sensor requiring only 19 mA of AC current. This sensor was successfully demonstrated as a level sensor for liquid nitrogen at atmospheric pressure. This simple approach to liquid cryogen level sensing in combination with different superconducting materials can be used to monitor the fill levels of many cryogenic liquids or cryogen temperatures altered by pressure by matching the superconducting secondary material transition temperature to the liquid cryogen in question.
References
1. J. Geng, et al., High-Tc superconducting transformer-rectifiers: principle, realization, and applications. SUST, 2025. 38(4): p. 043001.
2. A.C. Francis, et al., Electrical, magnetic and thermal circuit modelling of a superconducting half-wave transformer rectifier flux pump using Simulink. Superconductivity, 2023. 7: p. 100053.
3. A.C. Francis, et al., Jc(B) transformer rectifier flux pump optimisation via simulation. SUST, 2024. 37(12): p. 125005.
4. J.H.P. Rice, et al., Report On Progress Towards a 10 kA Transformer-Rectifier Flux Pump. IEEE TAS, 2024: p. 1-7.
5. Z. Wen et al., High Temperature Superconducting Flux Pumps for Contactless Energization. Crystals, 2022. 12(6): p. 766.