Grooved Permanent Magnet Structure for Lower Eddy Current Loss
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Solution Overview
Problem
Permanent magnet machines with single-tooth windings suffer from eddy current losses due to changing magnetic fields, leading to thermal overloading and potential failure, despite existing segmented magnet designs that only partially address this issue.
Innovation Solution
A permanent magnet with a non-straight groove configuration and groove depth less than its thickness, which reduces eddy currents, facilitates quicker assembly, and optimizes mechanical strength versus magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional segmented permanent magnets are used, then eddy current losses are partially reduced, but assembly complexity increases and manufacturing time is extended
Solution Approach 1:
The patent applies segmentation by introducing grooves that divide the permanent magnet into multiple magnetic segments. These grooves create magnetic isolation between segments, effectively reducing eddy current paths while maintaining a single-piece structural form that simplifies assembly. The segmentation is achieved through material removal (grooves) rather than physical separation into multiple components.
Solution Approach 2:
The patent merges the benefits of segmented magnet design with single-piece manufacturing. By incorporating grooves within a monolithic magnet structure, it combines the eddy current reduction advantage of segmented magnets with the assembly simplicity of single-piece magnets, eliminating the need for separate assembly operations while achieving magnetic segmentation.
2Loss of energy
If deeper grooves are introduced to reduce eddy currents, then eddy current losses decrease, but mechanical strength is compromised
Solution Approach 1:
The patent applies partial action by creating grooves with depth less than the full magnet thickness. This partial penetration is sufficient to interrupt eddy current paths and reduce losses while preserving the structural integrity and mechanical strength of the magnet. The grooves extend far enough to achieve magnetic isolation but not so deep as to compromise mechanical properties.
Solution Approach 2:
The patent applies local quality by concentrating the groove structure at specific locations where eddy currents are most problematic, rather than uniformly reducing magnet thickness throughout. The grooves are strategically positioned to maximize eddy current reduction while minimizing impact on overall mechanical strength.
3Ease of manufacture
If straight grooves are used, then manufacturing is simpler, but eddy current reduction effectiveness is limited
Solution Approach 1:
The patent applies curvature by using spiral or curved groove configurations instead of straight grooves. The spiral/curved geometry more effectively interrupts eddy current paths by creating longer, more complex current paths that are harder to maintain, thereby improving eddy current reduction effectiveness while remaining manufacturable through conventional machining or additive processes.
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 design effectively reduces eddy current losses, enhances the performance of electric machines, and simplifies the assembly process by allowing for a single-piece rotor with improved mechanical and magnetic properties.
Implementation Method 1
Permanent magnet machines, in particular permanent magnet machines with single-tooth windings, often suffer from losses due to eddy currents induced within the permanent magnets
Data Source
AI summary
A permanent magnet for use in an electric machine has a magnet thickness and extends along a magnet axis. The permanent magnet defines a groove extending axially along the magnet axis. The groove has a groove depth that is less than the magnet thickness. The groove has a non-straight configuration with respect to the magnet axis.