Surface PM Magnet Slit Layout for Eddy Current Loss Reduction
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Solution Overview
Problem
Surface permanent magnet motors face challenges in reducing eddy current losses, which are difficult to minimize due to the complexity and cost of segmented magnet assembly, and the resulting mechanical robustness issues.
Innovation Solution
A magnet design with slits on its surface, where the slit density is higher at the outer part than the inner part, disrupting eddy currents and reducing losses, while maintaining manufacturing ease and mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If segmented magnet blocks are used to reduce eddy current losses, then eddy current losses are reduced, but manufacturing complexity and assembly difficulty increase
Solution Approach 1:
The magnet body is segmented into multiple regions by providing slits at different densities - higher density at the outer part and lower density at the inner part. This segmentation disrupts eddy current paths while maintaining a single integrated magnet structure, avoiding the complexity of assembling multiple separate magnet blocks.
Solution Approach 2:
Different slit densities are applied to different regions of the magnet body - the outer part has higher slit density to address higher eddy current losses in that region, while the inner part has lower slit density. This localized approach optimizes eddy current reduction where needed without unnecessarily complicating the entire magnet structure.
2Loss of energy
If segmented magnet blocks are used to reduce eddy current losses, then eddy current losses are reduced, but manufacturing cost increases
Solution Approach 1:
The magnet is designed with slits that segment the magnetic material internally rather than requiring assembly of separately manufactured blocks. This reduces manufacturing cost by eliminating the need to produce, inspect, and assemble multiple magnet blocks while still achieving eddy current reduction.
Solution Approach 2:
The slit pattern is integrated directly into the magnet body design, combining the functions of eddy current reduction and structural integrity into a single manufacturing process. This eliminates the need for separate assembly operations and reduces overall manufacturing cost.
3Loss of energy
If segmented magnet blocks are used to reduce eddy current losses, then eddy current losses are reduced, but mechanical robustness decreases
Solution Approach 1:
The magnet body maintains its structural integrity as a single piece with slits cut into it, rather than being composed of multiple assembled blocks. This segmentation approach reduces eddy currents while preserving mechanical robustness, as there are no joints or interfaces that could weaken the structure.
4Loss of energy
If higher density slits are provided at the outer part, then eddy current losses are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The design accepts that different regions have different precision requirements - the outer part with higher slit density requires tighter spacing control, while the inner part with lower density has more tolerance. This localized approach to precision requirements makes the overall manufacturing process more feasible.
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 magnet design effectively reduces eddy current losses, improves motor efficiency, and simplifies the manufacturing process by minimizing material waste and assembly complexity.
Implementation Method 1
During operation of surface permanent magnet motors, eddy currents are induced in the permanent magnets. The eddy currents are generated as the rotor magnets rotate past the stator slot openings
Data Source
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AI summary
A magnet for a surface permanent magnet machine is provided. The magnet comprises a magnet body having a first surface, wherein the first surface comprises an inner part and an outer part, wherein the outer part is axially outwards of the inner part in use. The first surface comprises a plurality of slits, wherein a density of the slits is greater at the outer part than at the inner part. Also provided is a surface permanent magnet machine comprising at least one of the magnets, a surface permanent magnet motor comprising at least one of the magnets and an aircraft comprising the surface permanent magnet machine.