Internally Segmented Magnets for Eddy Current Loss Reduction
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Solution Overview
Problem
Permanent magnet motors in electric vehicles face efficiency reduction due to eddy current losses in sintered Nd—Fe—B magnets, which increase magnet temperature, and current methods to reduce these losses either deteriorate magnetic properties or increase manufacturing costs.
Innovation Solution
The development of internally segmented magnets with thin insulating layers made from ceramic mixtures, such as CaF2 and MgF2, that utilize eutectic reactions to lower melting points and enhance cohesive forces, allowing for thicker insulating layers without compromising mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the magnet is segmented by separating Nd-Fe-B magnets into thin slices with insulating materials, then eddy current losses are reduced, but manufacturing cost increases and manufacturing complexity increases
Solution Approach 1:
The magnet is divided into multiple magnetic layers separated by insulating layers, creating an internally segmented structure that reduces eddy current paths while maintaining magnetic performance
Solution Approach 2:
The insulating layer is formed as a composite material containing ceramic particles (such as alumina, silica, or magnesia) dispersed in a binder matrix, combining electrical insulation properties with mechanical strength and adhesion
2Loss of energy
If the insulating layer thickness is increased to reduce eddy current losses, then electrical insulation improves, but mechanical strength deteriorates
Solution Approach 1:
The insulating layer uses a composite formulation with ceramic particles providing electrical insulation and structural framework, while the binder matrix provides mechanical continuity and strength, enabling thicker layers without sacrificing mechanical properties
Solution Approach 2:
The insulating layer is designed with non-uniform ceramic particle distribution, concentrating insulating particles where electrical isolation is most critical while maintaining binder richness in regions requiring mechanical strength
3Temperature
If high coercivity magnets containing heavy rare earth elements are used to operate at elevated temperatures, then temperature resistance improves, but material cost increases
Solution Approach 1:
The patent converts the harmful effect of eddy current heating into a beneficial design feature by intentionally incorporating insulating layers that manage heat generation, allowing the use of more cost-effective magnet materials without heavy rare earth elements
Solution Approach 2:
The insulating layer acts as a thermal and electrical intermediary between magnetic layers, controlling heat transfer and electrical coupling to enable elevated temperature operation with standard magnet materials
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
This approach significantly reduces eddy current losses, improves mechanical properties, and decreases the need for expensive rare earth elements, thereby enhancing motor efficiency and reducing material costs.
Implementation Method 1
thin insulating layers made from ceramic mixtures, such as CaF2 and MgF2, that utilize eutectic reactions to lower melting points and enhance cohesive forces
Implementation Method 2
Due to the high conductivity of sintered Nd—Fe—B magnets and the slot/tooth harmonics, eddy current losses may be generated inside the magnets
Implementation Method 3
sintering the magnet stack
Data Source
AI summary
An internally segmented magnet is disclosed. The magnet may include a first layer of a permanent magnetic material, a second layer of a permanent magnetic material, and an insulating layer separating the first and second layers. The insulating layer may include a ceramic mixture of at least a first ceramic material and a second ceramic material. The mixture having a melting point of up to 1,100° C. and may be a eutectic, or near eutectic, composition. The magnet may be formed by forming a first layer of powdered permanent magnetic material, depositing an insulating layer over the first layer, depositing a second layer of powdered permanent magnetic material over the insulating layer to form an internally segmented magnet stack, and sintering the magnet stack. The ceramic materials may include a halogen and an alkaline earth metal, alkali metal, or a metal having a +3 or +4 oxidation state.