Design of a Cable System for a High-Power Density MVDC Aircraft Electric Power System

Electric power systems (EPS) for the future generation of electrified aircraft such as more electric aircraft (MEA) and all electric aircraft (AEA) are required to be high power delivery and low system mass. Due to the limited heat transfer by convection at the cruising altitude of a wide-body aircraft, designing cables for high power delivery and low system mass electric power systems (EPSs) based on typical standards e.g., IEC 60502 faces challenges such as thermal limits of the typical insulation systems. To design a low system mass cable system, aluminum should be used as the conductor and the overall diameter of the cable should be decreased. The former increases the joule losses of the cable, and the latter reduces heat transfer by radiation and convection, both resulting in exceeding the cable’s maximum permissible temperature. In this paper, a multi-layer insulation system for a ±5kV cable is designed for aircraft applications. The designed multi-layer insulation system experiences higher thermal conductivity and contains high-temperature materials such as AlN, PI, and PFA to compensate for the overall heat transfer reduction caused by decreasing the cable’s overall diameter. The designed multi-layer cable has a smaller thickness and a lower mass compared to insulation systems designed based on IEC 60502 standard. To determine the electric field and temperature field distributions across the designed insulation system a coupled study in COMSOL Multiphysics has been conducted. The main purpose of this study is to compare the designed multi-layer cable system’s overall diameter and mass to the cables designed based on IEC 60502 standard. Moreover, the obtained electric field distribution across the designed insulation shows that the designed insulation system is electrically safe.

I. Introduction

In recent decades, substantial research has been done in electrifying commercial aircraft to replace the mechanical, hydraulic, and pneumatic systems with electrical systems in more electric aircraft (MEA), and substituting the propulsion system with an electric system in all electric aircraft (AEA) in addition to the replacements mentioned above in MEA. Nevertheless, the state-of-the-art electrical propulsion systems are still not viable compared to conventional aircraft due to lower specific power [1]. According to [2], the required power density for future propulsion systems is approximately 40 kVA/kg. Since the electrical distribution and protection system stands for nearly 30% of the entire system’s mass, great potential resides in optimizing electrical systems [3]. Therefore, to achieve the advantages of electrified transportation, the most important task of researchers in this area is to develop an electrical system with high power delivery and low system mass. Among different components of EPS AEA, power cables connecting power electronic components, electric machines, electrochemical energy units, various loads, etc., form a significant portion of the total weight and volume of envisaged EPS AEA. In our earlier work, three medium voltage direct current (MVDC), ±5kVdc, bipolar EPS architectures were proposed and analyzed for an envisaged AEA [4].