Magnetic Signature Reduction by Converter Switching Frequency Modulation in Degaussing Systems

Wikkerink, Djurre; Mor, Armando Rodrigo; Polinder, H.; Ross, Robert T.

doi:10.1109/access.2022.3190616

Cited by 2 publications

(4 citation statements)

References 14 publications

(17 reference statements)

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“…The current ripple can be reduced by using an interleaved forward converter topology [16], but this will increase the losses because there are more components inside the cryostat [12]. Another solution to reduce the current ripple is to use a switching frequency modulation scheme [10].…”

Section: Discussionmentioning

confidence: 99%

“…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%

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Cryogenic H-Bridge Converter for HTS Degaussing Application

Wikkerink,

Gagić,

Mor

et al. 2024

IEEE Trans. Appl. Supercond.

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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.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Cryogenic H-Bridge Converter for HTS Degaussing Application

Wikkerink,

Gagić,

Mor

et al. 2024

IEEE Trans. Appl. Supercond.

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“…To compare different current source topologies, the specifications for the degaussing coils are needed. They are determined and taken from previous work [12]. A FEM model of a full-sized ship with 15 degaussing coils was constructed to find the rated current, I r , and inductance, L, of the degaussing coils.…”

Section: A Requirementsmentioning

confidence: 99%

“…It can be argued that is useful to use a higher switching frequency so that the current ripple can be lowered. Also a higher switching frequency causes the ripple in the magnetic signature to be damped more [12]. However, a higher switching frequency also causes more switching losses.…”

Section: B Switching Frequencymentioning

confidence: 99%

Converter Design for High Temperature Superconductive Degaussing Coils

Wikkerink

Mor²,

Polinder

et al. 2022

IEEE Access

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Detection of the magnetic signature of ships can be avoided by using a degaussing system; a set of on-board copper coils that compensates for the magnetic signature. High temperature superconductors (HTS) are currently investigated as a replacement for copper degaussing coils. By using HTS, we have to deal with higher currents and therefore with higher power supply losses. Also, large current leads are needed which introduces extra losses. This paper investigates different possible solutions to minimize these losses. Four H-bridge-based MOSFET topologies are presented that were designed to reduce the power supply and current lead losses. The first topology uses an H-bridge configuration so that the degaussing current can freewheel through the low-resistance MOSFETs. The second topology places the H-bridge inside the cryostat so that the current leads can be made smaller. The third topology includes a smoothing capacitor in the cryostat so that the current leads and input current are even smaller. The fourth topology uses a transformer so that the current leads can be eliminated. Measurements were done to determine the MOSFETs and capacitor performance in liquid nitrogen. The simulated losses of the four topologies are compared to determine the most energy-efficient option for supplying current to the HTS coils. It was found that by submerging multiple parallel MOSFETs in liquid nitrogen, the on-state resistance is decreased and the current supply can be made more efficient. Also, by placing a smoothing capacitor inside the cryostat, the current lead losses can be minimized significantly. The benefits of using a transformer do not outweigh the transformer losses.

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Magnetic Signature Reduction by Converter Switching Frequency Modulation in Degaussing Systems

Cited by 2 publications

References 14 publications

Cryogenic H-Bridge Converter for HTS Degaussing Application

Cryogenic H-Bridge Converter for HTS Degaussing Application

Converter Design for High Temperature Superconductive Degaussing Coils

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