Permanent Magnet Engine Machine Demagnetization After Coil Fault
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Solution Overview
Problem
Permanent magnet electric machines in aircraft propulsion systems face issues with unwanted power generation and drag after an internal coil fault, leading to heat generation and loss of thrust when the engine is not stopped, which is not a problem in other types of electric machines.
Innovation Solution
A method to reduce the magnetism of permanent magnets in a permanent magnet electric machine by increasing their temperature, using methods such as driving current through the stator assembly to induce eddy current losses, providing a heating fluid, reducing cooling, or injecting a fluid into the air gap, to irreversibly demagnetize the magnets and prevent further drag and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnet electric machines are used to generate electrical power during operation, then power density and efficiency are improved, but after an internal coil fault the machine generates unwanted power and heat causing drag on the driving engine
Solution Approach 1:
The patent applies parameter changes by heating the permanent magnets to demagnetization temperature (typically above 80°C depending on magnet material) to irreversibly reduce or eliminate their magnetic properties. This temperature parameter change transforms the magnets from a functional state to a non-functional state, stopping the unwanted electromagnetic generation while maintaining the physical integrity of the electric machine components
Solution Approach 2:
The patent converts the harmful effect of permanent magnets (continuous power generation causing drag) into a beneficial outcome by deliberately demagnetizing them. The harmful magnetic field is transformed into a controlled demagnetization process that eliminates the drag problem, effectively using the magnets' own magnetic properties against them to solve the fault condition
2Object-generated harmful factors
If the driving engine is stopped to halt unwanted generation, then heat generation is prevented, but thrust and power are lost
Solution Approach 1:
The patent extracts the harmful magnetic field generation capability from the electric machine by demagnetizing the permanent magnets. This separates the source of unwanted power generation (the magnetic field) from the mechanical drive system, allowing the engine to continue operating without the parasitic electromagnetic load that would otherwise require shutting down the entire propulsion system
3Device complexity
If permanent magnet electric machines are used, then simplicity is improved, but after fault the only way to halt generation is to stop rotation
Solution Approach 1:
The patent replaces the mechanical control method (stopping engine rotation) with a thermal control method (heating to demagnetize). Instead of using mechanical means to stop the electromagnetic generation, the system uses thermal energy to fundamentally alter the magnetic properties of the permanent magnets, providing a non-mechanical solution to a mechanically-based problem
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 method effectively reduces magnetism and prevents drag on the engine, maintaining operation by permanently demagnetizing the magnets, thus avoiding the need to stop the engine and minimizing adverse effects on thrust and power.
Implementation Method 1
a rotor assembly including one or more permanent magnets arranged circumferentially about a rotor axis and configured to generate a magnetic field; a stator assembly including a plurality of coils arranged circumferentially about a stator axis and in electrical communication with an electric transfer bus
Implementation Method 2
driving current through the stator assembly to induce eddy current losses
Implementation Method 3
driving current through the stator assembly to induce eddy current losses
Data Source
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AI summary
A method (200) for operating a permanent magnet electric machine of an engine includes (202, 204) determining a fault condition of the permanent magnet electric machine; and (206) reducing a magnetism of one or more permanent magnets of the permanent magnet electric machine by increasing a temperature of the one or more permanent magnets in response to determining the fault condition of the permanent magnet electric machine.