Live AC voltage
Development of alternative power electronics with "ERICOM" research project
Increasingly more components in modern passenger aircraft are electrically driven. This trend toward more electric aircraft is particularly evident with the aircraft types Airbus A380, A350 and Boeing 787. Frequency inverters are used to control compact direct drives that operate autonomously, but can also interoperate as networked components via digital interfaces in large systems. The AC voltage these inverters generate from the on-board electrical supply can be varied in terms of frequency and amplitude and is used to supply power directly to electrical machines. In aircraft, they are used for driving electric motors in compressors, starters and pumps.
Aircraft equipment such as frequency inverters, which the original equipment manufacturer (OEM) also includes in the test systems, has previously only been offered by a small number of manufacturers at extremely high costs. Moreover, replacement units are rarely available or have long delivery times. Diagnostics and repairs have also proved to be very difficult to date, because the controller technology in particular involves a number of unknowns and the OEMs do not provide the necessary information. For this reason, Lufthansa Technik does not use expensive OEM equipment in its test benches and has instead opted for a much more reasonably priced solution with frequency inverters that are widely used in industry.
The objective of the "ERICOM" (Electronics, Radios and Instruments for Components) research project, which ran from 2015 to 2017, was to replace the expensive OEM equipment with a standard industrial unit. A suitable frequency inverter had to be chosen and parameterized in order to ensure that the new system would behave in exactly the same way as the OEM systems typically used. For this purpose all previously defined quality features of the original power electronics were measured on active systems on an Airbus A380 in Frankfurt before alternative power electronics could be selected and the verification required for approval by the aviation authorities was performed. Finally, the measurements were then successfully validated on the alternative system built by Lufthansa Technik in order to demonstrate equivalence between the industrial components and the OEM aircraft equipment – that is, to show that they were in line with the test process with the same or better results.
There are significant advantages to using industrial components as opposed to the OEM aircraft equipment typically used to date. On the one hand, alternative power electronics allowed the test system to be developed in the first place, since important data such as the activation signals of the original equipment is not available. On the other hand, costs were reduced almost by a factor of 10, since the two original units were replaced by a traditional industrial drive system that enabled savings of several hundred thousand euros in the set-up of the test bench alone. Moreover, the improved understanding of the drive means that errors can be identified and resolved faster, thus increasing the availability of the test bench. The development of the test system that was made possible with "ERICOM" will save Lufthansa Technik several million euros over the coming years.