AC and DC Fault Management for Megawatt Electrified Aircraft Electrical Powertrains. Task 1: Circuit Breaker Design, Development, Testing and Evaluation

The NASA RTAPS program on AC and DC Fault Management for Megawatt (MW) Electrified Power Train is a multi-year joint project with Pratt & Whitney (P&W), Collins Aerospace (CA), and RTX Technology Research Center (RTRC). This research program focuses on high-voltage distribution issues that present a significant technological obstacle in the adoption of Electrified Aviation Propulsion (EAP) systems. One of the most significant issues to overcome for high-voltage electric distribution systems to meet the EAP vehicle weight and efficiency requirements are high-power density, low-loss circuit breakers to control power and clear faults. This issue is addressed by the first task of the NASA RTAPs program, wherein a 1.2 MVA direct current (DC) circuit breaker is developed to protect the EAP system battery and motor drive.

This report covers the development and testing of the 1.2 MVA circuit breaker that was developed by RTX NASA RTAPS program for application to electrified aircraft. The breaker is designed to achieve the following performance: 1.2 kV, 1 kA, 35 kft, <100 us response time, with > 99.5% efficiency at 100 kW/kg. Detailing the development and testing of the circuit breaker, this report is therefore segmented into the following:
•Down selection of the DC circuit breaker topology to achieve the lowest steady state losses in the smallest footprint.
•Critical enabling component designs: the additive manufactured cold plate, high-bandwidth current sensors, and transient voltage suppression circuit to achieve the aggressive target metrics of the program.
•Characterization of the solid-state circuit breaker and its components.
•Testing and validation of the solid-state circuit breaker under steady state loading and emulated high-altitude conditions to achieve target fault clearing time and to examine the long-term insulation challenges due to the potential of partial discharge effects.

This program was able to successfully meet or exceed all defined program metrics, as highlighted in the Summary Table. As a point of context, solid-state circuit breakers as they currently exist in the commercial marketplace offer a specific power density in the range of 10-20 kW/kg under an operational voltage of less than 300V. Thus, the outcome of this program task is a step towards electrified propulsion by providing a critical distribution element that is capable of 1.2 kV/1 kA operation, fast protection and a specific power density that is approximately 5x better than the state of the art.