Locally Tuned Rotor Lamination for Flux Leakage Reduction
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Solution Overview
Problem
Electric machines in electrified vehicles face inefficiencies due to magnetic flux leakage and conflicting property requirements for different regions within the rotor lamination, leading to reduced torque output and increased core loss.
Innovation Solution
The method involves fabricating rotor laminations using additive manufacturing techniques, where different powdered metals with varying compositions are used in specific regions to optimize magnetic permeability, mechanical strength, and core loss, allowing for locally-tuned properties within the lamination plane, such as using FeSi alloy for high permeability regions and non-ferromagnetic austenite stainless steel for reduced permeability in bridge areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform metal alloy is used throughout the rotor lamination, then manufacturing is simple, but magnetic flux leakage occurs and torque density is reduced
Solution Approach 1:
The rotor lamination is divided into different regions with different metal alloy compositions. Magnet pocket regions use high-permeability alloys (e.g., Fe-3%Si) to concentrate magnetic flux, while bridge regions use low-permeability alloys (e.g., Fe-14%Cr-12%Ni) to reduce magnetic flux leakage. This local differentiation of material properties optimizes torque density while maintaining manufacturing feasibility through additive manufacturing processes.
2Power
If high magnetic permeability material is used throughout the rotor lamination, then magnetic flux is concentrated, but magnetic flux leakage increases in bridge regions
Solution Approach 1:
Different regions of the rotor lamination are assigned different magnetic permeability characteristics based on their functional requirements. Magnet pocket regions utilize high-permeability materials to concentrate and guide magnetic flux, while bridge regions employ low-permeability materials to act as magnetic flux barriers, preventing unwanted flux leakage between adjacent magnet pockets.
Solution Approach 2:
The rotor lamination is constructed as a composite structure combining multiple metal alloy compositions within a single component. This includes high-permeability alloys for magnet pocket regions and low-permeability alloys for bridge regions, creating a functionally graded material distribution that simultaneously achieves magnetic flux concentration and leakage reduction.
3Power
If different metal alloys are used in different regions of the rotor lamination, then torque density increases, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process utilizes additive manufacturing technology that enables dynamic change of material composition during fabrication. By modifying the powder material composition at different spatial locations and process stages, the system can produce rotor laminations with region-specific alloy compositions (high-permeability in magnet pockets, low-permeability in bridges) without requiring complex assembly operations or multiple manufacturing steps.
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 enhances torque density and reduces core loss by strategically modifying the physical properties of the rotor lamination, improving the overall efficiency and mechanical strength of the electric machine.
Implementation Method 1
with a laser, fabricating a first region of a rotor lamination layer with a first powdered metal having a first composition
Implementation Method 2
fabricating, with a laser, a first region of a rotor lamination layer with a first powdered metal having a first composition
Data Source
AI summary
A rotor includes a rotor core lamination. The rotor core lamination includes a first metal alloy that at least partially defines adjacent magnet pockets proximate an outer periphery of the rotor core lamination. The rotor core lamination further includes a second metal alloy different than the first metal alloy that forms at least a portion of a bridge that extends between the magnet pockets. The rotor core lamination further includes permanent magnets disposed in the magnet pockets at opposing sides of the second metal alloy.