Composite Axial Flux Rotor With Halbach Array for Low Eddy Loss
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Solution Overview
Problem
Axial flux machines in aerospace applications face challenges such as high rotor mass, eddy current losses, magnetic flux inefficiency, and structural integrity issues due to high rotational speeds and centripetal forces, which affect power density, reliability, and safety.
Innovation Solution
A composite rotor body made of fibre reinforced materials, specifically a sheet moulded composite (SMC), replaces traditional metal components, incorporating a Halbach magnet array and dual ring structures for enhanced magnetic efficiency, structural support, and safety redundancy, while minimizing mass and eddy current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a ferromagnetic steel backplane is used in the rotor, then magnetic flux conduction is improved, but eddy current losses increase and rotor mass increases
Solution Approach 1:
The patent applies composite materials by combining a non-magnetic composite matrix (such as fibre-reinforced plastic) with embedded permanent magnets to create a rotor structure that eliminates eddy current losses while maintaining magnetic flux conduction through the magnetic magnets themselves and eliminating the need for a ferromagnetic steel backplane, thereby reducing rotor mass
2Reliability
If surface mounted magnets are used on the rotor, then manufacturing ease is improved, but magnet adhesion reliability deteriorates under high centripetal forces
Solution Approach 1:
The patent applies local quality by embedding magnets directly into cavities or slots formed in the composite rotor body during the manufacturing process, providing localized mechanical interlocking and adhesive bonding that secures magnets against high centripetal forces while maintaining manufacturing efficiency through integrated成型
Solution Approach 2:
The composite rotor body material provides both structural integrity and magnet retention through the combination of matrix material and reinforcement fibres, creating a robust embedding structure that holds magnets securely under high rotational speeds
3Power
If rotor speed is increased to improve power density, then power output is improved, but centrifugal forces on magnets increase causing safety risks
Solution Approach 1:
The fibre-reinforced composite rotor body provides high specific strength and stiffness that can withstand the high centrifugal forces generated at elevated rotational speeds, enabling the rotor to operate at higher speeds for improved power density while maintaining structural integrity and magnet retention
Solution Approach 2:
The embedded magnet structure with mechanical interlocking and adhesive bonding provides pre-established retention mechanisms that counteract centrifugal forces before they can cause magnet detachment, ensuring rotor integrity at high speeds
4Weight of moving object
If a non-magnetic composite rotor body is used, then eddy current losses are reduced and mass is reduced, but structural stiffness may be insufficient
Solution Approach 1:
The patent uses fibre-reinforced composite materials (such as carbon fibre or glass fibre reinforced plastic) that provide high specific stiffness and strength, enabling the non-magnetic rotor body to maintain sufficient structural rigidity while achieving significant mass reduction compared to traditional ferromagnetic steel rotors
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 SMC rotor body achieves a significant reduction in mass (>50%) and eddy current losses (85%), improves magnetic efficiency, and provides multiple layers of safety redundancy, enhancing structural integrity and reliability for high-speed aerospace applications.
Implementation Method 1
ferromagnetic steel is conductive and eddy current losses are generated during use. To reduce eddy currents, it is possible for the annular ring to hold a soft magnetic material, the soft magnetic material being soft magnetic powder composite or laminated electrical steel
Implementation Method 2
The rotor bears a set of permanent magnets and is mounted on a bearing so that it can rotate about the axis driven by fields from the stator coils
Implementation Method 3
A first Halbach magnet array is mounted on a first face of the rotor body circumferentially around an axis of rotation of the rotor body
Data Source
AI summary
A rotor for an axial flux machine, the rotor comprising: a disc-shaped rotor body having an axis of rotation, the disc-shaped rotor body formed of a fibre reinforced composite material and having an opening at the axis of rotation; a plurality of permanent magnets mounted to a first face of the rotor body circumferentially around the axis of rotation, the plurality of permanent magnets arranged in a Halbach array configuration.