Lifetime Characterisation Of Components Exposed To High Voltage Gradients
Work Package Leader: Prof. Andrea Cavallini
To analyze the impact that higher voltage gradients on the lifetime of electrical machines and the connecting cables / connectors. To define verification / qualification methods for materials and systems used in aircraft applications and to provide recommendations for the design of insulation systems when using high voltage gradient systems..
This task will quantify the impact that higher voltage gradients will have on the lifetime of electrical machines and the connecting cables / connectors. The task will focus on systems that cannot be guaranteed partial discharge free and that will likely have a limited life. It will quantify the impact of any measures identified in WP 1 and 2.
In particular, a preliminary investigation plan will involve:
- Accelerated life tests consisting of aging sub-cycles. Each sub-cycle will consist of thermal cycling (from a low temperature to a high temperature), mechanical stress, and a diagnostic test aimed at showing that the insulation models are PD-proof or still able to withstand a specified voltage level. The tests will be carried out with a maximum temperature 20 K below the maximum prescribed by IEC 60034-18-21. Tests performed with low thermal cycling will be compared with other performed without the cooling phase, to highlight the effect of low temperatures on the integrity of the insulation. Furthermore, the lifetimes obtained by the two procedures will be compared to understand whether an insulation system qualified for industrial purposes (reference system) is sufficiently reliable for aircraft application.
- Electrical life tests (terminated with insulation breakdown) at various frequencies. The models will be immersed in mineral oil to prevent PD inception. These tests are aimed at verifying whether frequency scaling still holds at frequencies as large as 200 kHz or if phenomena not incepted at typical industrial frequencies (e.g. a dielectric loss peak, different SCLF profiles) come into play worsening the degradation rate of the insulation.
- Electrical life tests similar to 2 but with same frequency and different rise times
Effect of managing the voltage gradients through alternative designs of insulation or winding systems will also be analyzed .
This analysis will lead to an update of the defined verification / qualification methods defined in WP 2. The task will provide recommendations for the design of insulation systems when using high voltage gradient systems and Type/Qualification test guidelines for the verification of complete stators.