High Temperature Superconducting Degaussing–cooling Two HTS Coils With One Cryocooler for the Littoral Combat Ship

The magnetic modelling and experimental validation of a superconducting degaussing system for maritime vessels is discussed. Degaussing coils compensate for the distortion in the earths' magnetic field by the magnetized steel hull of a ship, thus rendering it 'invisible' for magnetic field sensors. Whereas typical power requirements with copper coils are of the order of 100 kW, a ReBCO HTS degaussing system in principle allows to reduce this by an order of magnitude. In order to validate such efficiency estimates and to demonstrate the required hardware, a table-top test setup was realized with magnetic ship steel. The vessel-imitating cylindrical demonstrator is equipped with six degaussing coils, grouped in three sets that act in two different directions, with each set consisting of one copper and one ReBCO coil, the latter one equipped with a sub-cooled forced-flow liquid nitrogen system. Static magnetic field measurements are reported and compared to both analytical and numeric finite element models. The results illustrate how even relatively simple analytical models can be used as a powerful tool to extrapolate design parameters and thus to predict the power requirements of large-scale degaussing systems.

Section: Introductionmentioning

confidence: 99%

Modeling and Characterization of a ReBCO HTS Degaussing Demonstrator

Hanse

Wikkerink

Keijzer

et al. 2022

“…The variation of resistance of HTS lap joints with compressive joint pressure is the subject of this paper. An HTS degaussing technology demonstrator has been assembled and tested at the Naval Warfare Center Carderock Division in Philadelphia [1]. This system is representative of the systems that might be installed on the next generation of Navy ships.…”

Section: Introductionmentioning

confidence: 99%

Resistance of Demountable Mechanical Lap Joints for a High Temperature Superconducting Cable Connector

Dietz

Audette

Bromberg

et al. 2008

Experiments conducted to determine the resistance of demountable HTS lap joints with variations in compressive stress are reported here. A joint fixture was constructed that enabled the simultaneous testing of multiple joints of different configurations. The joint fixture was installed in a loading facility, comprising a pneumatic press mounted in a vacuum bell jar and connected to a GM cryocooler. The resistance across each joint was measured by means of voltage taps over a range of compressive joint forces.The test results demonstrated that joint resistances less than 2 were possible with only light joint loading.

“…The feasibility of using HTS degaussing coils is currently under investigation. The US Navy tested a ship with a full-size HTS degaussing coil in 2011 [6] using a cryostat with gaseous helium [7] and connecting multiple cryostats to a single cooler [8]. In work preceding this article, a theoretical comparison between HTS and copper coils has been made [4], [5], a scaled demonstrator was built with HTS and copper degaussing coils [9], the current ripple in HTS degaussing coils was investigated [10], and a converter was designed for HTS degaussing coils [11], [12].…”

mentioning

confidence: 99%

Cryogenic H-Bridge Converter for HTS Degaussing Application

Wikkerink,

Gagić,

Mor

et al. 2024

A degaussing system can be used to reduce the detectability of the magnetic signature of a ship. Commonly, a degaussing system consists of a set of onboard copper coils that produce a magnetic field to compensate for the magnetic signature. High-temperature superconductive degaussing coils are considered an alternative to copper degaussing coils because of a reduction in energy losses, weight, volume, and costs. The losses of a high-temperature superconductor (HTS) degaussing system can be reduced even further by powering it with a cryocooled converter with parallel MOSFETs. A low-duty cycle and smaller current leads can be used. These solutions eliminate most of the power source losses. This article investigates such a cryocooled converter. The effect of the low switching frequency on the converter performance is tested. A prototype that can operate at cryogenic temperatures was built. The converter powers an HTS coil. It was found that a load current of 50 A can be achieved with a duty cycle of just 0.025 at an input voltage of 3.5 V while still meeting the requirement of a maximum current ripple of 0.5%. At a switching frequency higher than 100 Hz, the converter's performance deteriorates. Also, oscillations were observed in the circuit. This is a problem due to the low blocking voltage of the MOSFETs. The parasitic inductances in the circuit have a high impact on the performance because the resistance in the circuit is very low.