Nested V-Shaped Rotor Pockets for Torque Ripple Reduction
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Solution Overview
Problem
Electric machines experience undesirable torque oscillations due to harmonics in the airgap flux and permeance, leading to torque ripple, which can be mitigated through proper rotor design.
Innovation Solution
The rotor design incorporates nested V-shaped inner and outer pockets with specific pole arc angles and bridge widths, optimized to house inner and outer magnets, ensuring a ratio of corresponding pole arc angle dependent functions and a ratio of inner to outer widths, thereby shaping the magnetic field to minimize torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional rotor design is used, then manufacturing is simpler, but torque ripple increases due to harmonics in airgap flux and permeance
Solution Approach 1:
The rotor magnet structure is segmented into multiple discrete magnets arranged in specific patterns (e.g., V-shaped, nested V-shaped, or X-shaped arrangements). Each magnet can be independently positioned and sized, allowing precise control over the magnetic field distribution in the airgap. This segmentation enables cancellation of harmonic components that cause torque ripple while maintaining a manageable assembly structure.
Solution Approach 2:
Different regions of the rotor are designed with locally optimized magnet configurations. For example, magnets in different zones may have different widths, polarities, or orientations to create specific magnetic field characteristics in different airgap regions. This local optimization allows tailored control of flux distribution to minimize torque ripple in critical areas while maintaining overall rotor performance.
2Object-generated harmful factors
If magnet size and arrangement are optimized to reduce torque ripple, then torque smoothness improves, but manufacturing precision requirements increase
Solution Approach 1:
The rotor employs asymmetric magnet arrangements where magnets are deliberately positioned with different widths, spacing, or orientations rather than uniform symmetry. For example, V-shaped or X-shaped patterns create intentional asymmetries that generate compensating magnetic fields to cancel torque ripple. These asymmetric designs are engineered to be robust to typical manufacturing tolerances while achieving torque smoothing.
Solution Approach 2:
The rotor structure implements nested magnet arrangements where smaller magnets are positioned within or between larger magnets, creating multiple levels of magnetic field interaction. This nested configuration allows lower-order harmonics to be cancelled by the outer magnets while inner magnets address higher-order harmonics, achieving comprehensive torque ripple reduction through hierarchical harmonic cancellation.
3Power
If multiple nested V-shaped pockets are used, then magnetic field control is improved, but device complexity increases
Solution Approach 1:
Multiple V-shaped magnet pockets are merged into integrated structural units that share common support features, such as a shared central bridge or common mounting surface. The nested V-shaped pockets are positioned to utilize the same structural framework, reducing the number of discrete components and simplifying manufacturing while maintaining the complex magnetic field control benefits of multiple pockets.
Solution Approach 2:
The nested V-shaped pocket structure serves multiple functions simultaneously: it provides mechanical support for multiple magnets, defines precise magnetic pole positions, creates flux leakage paths for harmonic cancellation, and establishes geometric relationships that control airgap flux distribution. This multi-functionality reduces the need for separate components and simplifies the overall rotor design.
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 design enhances the magnetic field direction and magnitude, optimizing electric machine torque and reducing torque ripple, as demonstrated by the graphs showing maximized average output torque and minimized peak-to-peak torque ripple when the magnet width ratio matches the ratio of corresponding pole arc angle dependent functions.
Implementation Method 1
The magnetic field generated by the stator may cooperate with permanent magnets within the rotor to generate torque
Data Source
AI summary
A rotor includes nested V-shaped inner and outer pockets defining corresponding pole arc angles relative to a common center bridge axis and vertex, respective inner and outer top bridges, and respective inner and outer center bridges. A ratio of corresponding pole arc angle dependent functions and a ratio of a sum of the inner top bridges and center bridge widths to a sum of the outer top bridges and center bridge widths are same.