Current Steering in DC Superconducting Electrical Systems for Aerospace

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Abstract

Reduced emissions and greater fuel efficiency in the aerospace industry is the focus of current research and literature. The Flightpath 2050 initiative is a large driving force behind this, as the initiative requires a 75% reduction in C02 emissions per passenger kilometre by 2050 when compared to C02 emissions in 2000 [1]. The drive for greater fuel efficiency and reduced emissions is also partly due to fuel costs and airline competition. Current research suggests that the use of conventional conductors and machines becomes more problematic the higher the power levels rise, due to size and weight of the conductors for the required power level. However, in [2] the authors discuss the possibility of utilising a DC superconducting system. If a superconducting electrical system was to be designed it may be fair to assume that the architecture would include parallel superconducting cables. However, because of the zero resistance under DC conditions in the superconductor, it is uncertain how two parallel superconducting cables would share their current as in normal conductors the resistance defines the current sharing. A basic Simulink model was designed and simulated to establish how the current would share in two parallel superconducting DC cables. The cable inductance was found to be a significant factor in current sharing. This was tested experimentally using two parallel YBCO wires in a superconducting test tank at 77K. The experimental results closely matched with the MATLAB model, thus validating the model. If the current sharing is asymmetric a current steering device would be needed to balance the currents in the branches of the circuit, to avoid the risk of one branch superconducting quenching and all the issues associated with it. Various possible solutions were simulated in MATLAB Simulink model; the optimal solution was to inject a DC voltage into a superconducting branch, the increase in voltage would modify the current in that branch and this changes the current distribution in the other superconducting branches. A current steering device with a coil wound around a ferrite core was designed and built to inject the DC voltage. This was then put in the superconducting test tank with one of the YBCO superconducting branches passing through the core window and tested experimentally. The experiment successfully demonstrated that the current can be steered from one superconducting branch to another by injecting a DC voltage into one of the superconducting branches, thus validating the MATLAB Simulink model.

Keyword(s)

Distributed electrical aerospace electrical systems; Future aircraft electrical systems; Superconducting current sharing; Superconducting current steering

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