Aircraft Electric Machine Depressurization for Breakdown Prevention
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Solution Overview
Problem
Electric machines in aircraft face electrical breakdown and arcing issues at high altitudes due to low air pressure, which current voltage derating methods cannot fully address, especially in high-voltage applications like hybrid gas turbine engines or distributed propulsion systems.
Innovation Solution
An electric machine with a depressurization system that reduces the pressure inside its casing below external gas pressure, using a combination of labyrinth or dry gas seals and a vacuum pump controlled by a pressure sensor and controller to maintain a pressure that prevents electrical breakdown, increasing the voltage required for electron avalanche initiation beyond operational levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage derating is applied to prevent electrical breakdown, then reliability improves, but power output decreases
Solution Approach 1:
The patent changes the pressure parameter inside the casing by introducing a depressurisation system. By reducing the gas pressure from atmospheric levels to a lower pressure environment, the dielectric strength of the gas increases, allowing the electric machine to operate at higher voltages without electrical breakdown. This resolves the contradiction by enabling full power output while maintaining reliability through pressure modification rather than voltage reduction.
2Reliability
If gas pressure inside casing is reduced to prevent electrical breakdown, then reliability improves, but device complexity increases
Solution Approach 1:
The patent creates a controlled low-pressure environment inside the casing that acts as an inert atmosphere with respect to electrical breakdown. By reducing the gas pressure, the environment becomes less conducive to electrical discharge, effectively protecting the internal components. This approach uses environmental modification rather than complex protective structures, resolving the contradiction by achieving reliability through a relatively simple pressure control system rather than complex shielding or insulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents electrical breakdown and arcing by reducing the likelihood of collisions between gas molecules within the casing, ensuring the electric machine operates safely and efficiently in low-pressure environments without voltage derating, thus enabling reliable operation in aircraft systems.
Implementation Method 1
increases the voltage required for electron avalanche initiation to a point greater than the peak operational voltage within the casing, thereby preventing electrical breakdown
Implementation Method 2
The seal may comprise a labyrinth seal or a dry gas seal, or combination of the two.
Data Source
AI summary
An electric machine (101) for use in an aircraft is shown. The electric machine comprises a casing (104) containing electromechanical components, a shaft (106) which extends outside of the casing, a seal (107) to seal the casing around the shaft, and a depressurisation system (102) configured to depressurise the casing below an external pressure to prevent electrical breakdown within gas in the casing.