Axial Air Gap Rotor Magnet Retention With Thin Protective Layer
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Solution Overview
Problem
Existing electrical machines for aircraft require improved safety and efficiency while minimizing weight and avoiding the inefficiencies associated with reduced magnetic material area.
Innovation Solution
An electrical machine with an axial air gap featuring a stator, rotor, permanent magnets, and a protective layer made of fiber-reinforced plastic, where the holding section of the rotor extends over the protective layer to securely attach the magnets, reducing the risk of breakage and allowing for a smaller gap width between the rotor and stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If magnets are bonded together with outer ring, rotor disk, and magnet cover, then fixation and vibration damping are improved, but safety and security against breakage are insufficient
Solution Approach 1:
A protective layer is applied to the permanent magnets before assembly to prevent breakage. This protective layer acts as a cushioning element that absorbs stress and prevents the brittle magnetic material from shattering during operation or if damage occurs.
Solution Approach 2:
The solution combines the permanent magnet material with a protective layer material to create a composite structure. This composite design leverages the strengths of both materials - the magnetic properties of the magnet and the protective qualities of the outer layer - to achieve both fixation and safety.
2Reliability
If many very small magnets each housed in own casing are used, then safety is improved, but area covered by magnetic material decreases leading to efficiency loss
Solution Approach 1:
Instead of housing each small magnet separately, the solution segments the protective function by applying a continuous protective layer that covers multiple magnets. This maintains the safety benefits of protected individual magnets while preserving the magnetic material area for efficiency.
Solution Approach 2:
The protective layers of individual magnets are merged into a single continuous protective structure that spans multiple magnets. This combining approach maintains the safety of individual magnet protection while eliminating the space losses associated with separate casings for each magnet.
3Productivity
If protective layer is made thin, then gap between rotor and stator is reduced improving efficiency, but retention of fragments may be compromised
Solution Approach 1:
The protective layer uses composite materials that provide both thin profile and high fragment retention capability. The composite structure allows the layer to be sufficiently thin for efficiency while maintaining the strength needed to contain magnetic fragments if breakage occurs.
Data Source
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AI summary
An electrical machine (1) with an axial air gap (S), in particular for an aircraft (2), comprises: a stator (10), a rotor (11) rotatable relative to the stator (10), at least one permanent magnet (12A-12D) which is positively engaged on the rotor (11) by a retaining section (110) of the rotor (11) on a base (111) of the rotor (11), and a protective layer (13A-13D) which covers a side (120) of the at least one permanent magnet (12A-12D) facing the stator (10), wherein the retaining section (110) of the rotor (11) overlaps the protective layer (13A-13D).