Axial Groove Patterns for Permanent Magnet Rotor Torque Ripple
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Solution Overview
Problem
Permanent magnet machines in electric vehicles experience torque ripple due to harmonic components in electromagnetic flux, leading to vibration and noise, which existing designs fail to adequately mitigate.
Innovation Solution
A rotor configuration with multiple sections, each comprising axially stacked laminations defining unique patterns of axial grooves on the circumferential surface, where the groove patterns differ between sections and repeat at specific pole intervals, offsetting pole locations to reduce harmonic torque components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional rotor design with uniform surface is used, then the structure is simple and easy to manufacture, but torque ripple and vibration noise occur due to harmonic components in electromagnetic flux
Solution Approach 1:
The rotor is divided into multiple sections along the axial direction, with each section having distinct groove patterns. This segmentation allows different harmonic components to be addressed by different sections, reducing overall torque ripple while maintaining manageable structural complexity
Solution Approach 2:
Different axial grooves are introduced at specific locations (sections) of the rotor rather than uniformly across the entire rotor. Each groove pattern is locally optimized to reduce specific harmonic components, achieving effective torque ripple reduction with controlled structural complexity
2Object-affected harmful factors
If axial grooves are introduced to reduce torque ripple, then vibration and noise are minimized, but the manufacturing complexity increases
Solution Approach 1:
The rotor structure is segmented into sections with different groove patterns that can be manufactured separately and then assembled. This approach reduces the overall manufacturing complexity compared to creating a single complex groove pattern across the entire rotor surface
Solution Approach 2:
The groove patterns are designed with specific geometries and distributions that dynamically interact with the electromagnetic flux to reduce torque ripple. The varying groove patterns across sections provide the necessary dynamic characteristics to mitigate vibration and noise while maintaining manufacturability
Data Source
AI summary
A permanent magnet electric machine includes a rotor configured to rotate about an axis. The rotor is comprised of axially stacked sections. Each section is comprised of axially stacked laminations that define a pattern of axial grooves on an outer surface of the rotor to reduce torque ripple. The pattern is different for at least two of the sections. The pattern for each section may alternate with respect to poles of the rotor.