Optimisation of High Voltage Electrical Systems for Aerospace Applications

Abstract

Increased electrical power demands are being experienced on the new generation ofaircraft due to an increased reliance on electrical technology of systems such as airconditioning, de-icing systems and electrical flight control actuation. Distribution of powerat higher AC and DC voltages is therefore now being seen in modern aircraft to avoid thepenalties incurred due to high cable weights. Voltages have increased past the minimum ofPaschen's law resulting in a risk that life limiting partial discharge (PD) damage can occurin the insulation systems. This thesis uses a theoretical analysis backed by PD experimentalresults to investigate the optimal operating voltage of a cabling system. In addition, itproposes a methodology for optimizing the operating voltage level based on an analysis ofthe power carrying capability of cabling within a fixed and a non-fixed volume system andthe derivation of the cable weight as a function of voltage. Furthermore the power carryingcapability of a certain round cable system is compared with an insulated flat conductorsystem as in a printed circuit board (PCB). An initial assessment has been carried out todetermine whether more power can be delivered via insulated flat solid conductors as in aPCB, instead of using round cables. The reason why there is a need to investigate thisaspect, is because using new PCB technology can offer several advantages over traditionalcabling harnesses. The work done has shown that the optimal operating point (e.g.maximum power to weight ratio) for an aircraft power system, does not improve aftercertain voltage levels. A tradeoff between cable weight and power transfer is required andfurthermore the use of DC systems can result in higher power transfers than conventionalthree phase/400Hz AC systems. The PCB maximum power transfer assessment has alsoshown that insulated flat conductor systems can offer higher power transfer efficiencies. Inaddition, experimental AC and DC PD tests on certain unscreened aerospace cables (laidout in different configurations), have shown that the theoretical analysis employed todetermine cable safe operating voltages gives conservative results.

Date of Award	31 Dec 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Ian Cotton (Supervisor)