Shell Magnet Rotor Recesses for Torque Ripple Reduction
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Solution Overview
Problem
Existing electrical machines with permanent magnet rotors experience torque ripple and cogging due to magnetic interactions between stator and rotor poles, which can negatively impact speed control and operational efficiency.
Innovation Solution
The electrical machine incorporates shell-shaped magnet segments with magnetically differently polarized sections, featuring recesses as outer and inner pole elevations, particularly designed to reduce torque ripple and cogging by optimizing magnetic transitions and flux density distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If magnet segments with simple flat end sections are used, then the structure is simple and easy to manufacture, but torque ripple and cogging increase due to unfavorable magnetic transition between magnet segments
Solution Approach 1:
The invention applies local quality by providing recesses specifically in the transition zones between magnetically differently polarized sections of the magnet segments, while leaving other areas unchanged. This localized modification creates inner pole elevations that specifically address the magnetic transition problem at pole boundaries without requiring complete redesign of the entire magnet segment structure
Solution Approach 2:
The recesses in the transition zones are designed with curved cross-sectional profiles (circular segments, arcs, or rounded corners) rather than sharp angular shapes. This curvature creates a gradual magnetic transition between poles, reducing the abrupt field changes that cause cogging and torque ripple while maintaining manufacturing feasibility
2Object-generated harmful factors
If pole lifts are produced by flattening end sections of magnet segments, then magnetic transition between magnet segments is improved, but further reduction of torque ripple requires additional complex design measures
Solution Approach 1:
The invention segments the approach to pole elevation by creating distinct outer pole lifts at the edge zones and inner pole lifts in the transition zones of magnet segments. This segmentation allows each type of pole lift to be optimized for its specific function: outer pole lifts for overall magnetic transition and inner pole lifts for transition zone smoothing, achieving better torque ripple reduction without requiring complete redesign
Solution Approach 2:
The invention modifies the geometric parameters of the magnet segments by introducing recesses with specific cross-sectional profiles (defined by radii, depths, and widths) in the transition zones. These parameter changes create inner pole elevations that adjust the magnetic field distribution, reducing cogging torque peaks while maintaining a relatively simple overall structure
3Object-generated harmful factors
If uniform flux density distribution is achieved through complex cross-sectional profiles, then cogging torque peaks are reduced, but manufacturing complexity increases
Solution Approach 1:
The recesses in the transition zones are designed with curved cross-sectional profiles (circular segments, arcs, or rounded corners) rather than sharp angular shapes. This curvature creates a gradual magnetic transition between poles, reducing the abrupt field changes that cause cogging and torque ripple while maintaining manufacturing feasibility through standard machining operations
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 cogging torque and associated torque ripple, resulting in a smoother operation of the electric machine by enhancing the magnetic transition and flux density distribution, leading to a more even rotation.
Implementation Method 1
a magnetic interaction of the stator poles with the rotor poles
Implementation Method 2
each have a plurality of magnetically differently polarized sections in the circumferential direction, each of which forms a magnetic pole of the rotor
Implementation Method 3
achieves a particularly uniform flux density distribution in the circumferential direction
Data Source
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AI summary
The invention describes an electrical machine comprising a stator and a rotor which is separated from the stator by an air gap and has a plurality of shell-like magnet segments which are fastened to a magnetic return path element. In this case, the magnet segments are arranged opposite one another in pairs in each case and each have a plurality of magnetically differently polarized sections in the circumferential direction, said sections each forming a magnetic pole of the rotor. In this case, recesses which each serve as outer detached pole portions are provided on that side which faces the stator in the edge zones of the magnet segments which are arranged in the circumferential direction. Furthermore, further recesses are provided on that side which faces the stator in the transition zones between the magnetically differently polarized sections of the magnet segments, said recesses serving as inner detached pole portions.