Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - DiDi-FaCT (Diode Die Fatigue Characterisation and Testing)

Teaser

Future aircraft will use a large amount of electrical power. Not only are extra systems needed for e.g. in-flight entertainment, communication and passenger comfort, but more importantly there is a trend to replace aircraft systems powered by oil or hot engine air (bleed air)...

Summary

Future aircraft will use a large amount of electrical power. Not only are extra systems needed for e.g. in-flight entertainment, communication and passenger comfort, but more importantly there is a trend to replace aircraft systems powered by oil or hot engine air (bleed air) by electrical systems. This means that aircraft electrical generators must be scaled up accordingly. How can this be done safely and reliably, without making the equipment too heavy?
One solution is running the generators at a high speed, which results in better power density, but also puts a lot more stress on the rotor and on rotor-mounted electrical diodes. The environment wasn’t very friendly to start with, with high temperatures and high mechanical forces, and the extra stress is making it worse. How can we be sure that the generator doesn’t fail prematurely due to diode fatigue?
In the DiDi-FaCT project a long-term thermo-mechanical stress test will be performed on multiple diode types, in order to derive and validate an aging model of the component. The model allows designers that apply power electronic components in harsh environments to optimise the construction of the packaging so that it has the required long-term reliability. This is an essential step towards obtaining large weight and efficiency improvements in generators and other equipment, which in turn leads to reduced fuel consumption and emissions of the aircraft.

Work performed

In 2016, analyses were performed on how the electrical components (diodes) will be tested in a test bench that will be specifically designed for the project. In the bench, the diodes will be exposed to long-duration fatigue testing. A preliminary test programme was developed, and a preliminary design of the test bench was developed, and reviewed during the preliminary design review. In 2017, the bench will be designed in detail, manufactured and testing of the components will commence.

Final results

\"Use of optimised power-electronic components allows generators and starter/generators to become lighter and smaller. New technology can dramatically increase the electrical performance, leading to lower losses, which means the generator wastes less energy and also requires less cooling, which saves weight and therefore fuel. However, technology must remain safe and reliable and therefore testing is needed before these advances can be made. Furthermore, life predictions methods are required to design optimal configurations that perform reliably under harsh conditions.
One of the main impacts of the Clean Sky Systems Work Plan topic \"\"Power Generation\"\" is “innovative rotor design suitable for high centrifugal forces”. An essential part of the design of a high-speed rotor with rotor-mounted rectifier bridges is the reliability of the diodes. DiDi develops a better understanding and a predictive capability for diode dies under such large centrifugal and thermal stresses. This enables creating package and rotor designs with a high performance that are also reliable, which is crucial in the marketplace.
If the European industry can provide lighter, more efficient generators it clearly has a competitive advantage. European aircraft integrators benefit by having advanced-technology generators available from European suppliers. However, as said, reliability must be guaranteed if a successful product is to be made. DiDi ensures that the new components operate reliably under the most severe conditions encountered. This will maintain the advantage of European suppliers over emerging suppliers.\"