Patterned Offset Pole Rotor for Torque Ripple Reduction
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Solution Overview
Problem
Electric machines in electrified vehicles face challenges in reducing torque ripple and achieving balanced rotor performance due to limitations in existing skewing methods, particularly in designs with shorter stack lengths and varying magnetic flux harmonics.
Innovation Solution
The proposed solution involves a rotor assembly with laminations arranged such that pairs of angles between magnetic axes and interpolar axes define a repeating sequence, allowing for both axial and radial skewing to reduce torque ripple and enhance rotor balancing, noise reduction, and magnetic flux harmonics. This includes specific angle distributions and resequencing of poles to maintain symmetry and optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional skewing methods are used in rotor design, then manufacturing simplicity is maintained, but torque ripple reduction is insufficient
Solution Approach 1:
The patent applies asymmetry by implementing different skew angles for different pole pairs in the rotor. Specifically, first and second pole pairs have a first skew angle, while third and fourth pole pairs have a second skew angle that is different from the first. This asymmetric skewing pattern creates intentional magnetic flux distribution variations that reduce torque ripple and improve rotor performance without complicating the manufacturing process excessively.
2Ease of manufacture
If uniform skewing is applied to all poles, then manufacturing is simplified, but rotor balancing and noise reduction are compromised
Solution Approach 1:
The patent implements local quality by applying different skewing characteristics to different regions of the rotor. Specifically, adjacent pole pairs (first and second) have a first skew angle, while other adjacent pole pairs (third and fourth) have a second skew angle. This localized variation in skewing angles optimizes magnetic flux distribution in specific rotor regions, thereby reducing noise and vibration without requiring complete redesign of the entire rotor structure.
3Length of moving object
If stack length is reduced to meet design constraints, then device size is minimized, but torque ripple increases
Solution Approach 1:
The patent applies parameter changes by modifying the skew angle parameter to compensate for reduced stack length. By implementing specific skew angles (first skew angle for first and second pole pairs, second skew angle for third and fourth pole pairs), the design maintains optimal magnetic flux distribution even with shorter stack length, thereby reducing torque ripple while meeting size constraints.
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 solution effectively reduces torque ripple, improves rotor balancing, and minimizes noise and vibration (NVH) while maintaining efficient magnetic flux and voltage harmonics, enhancing the overall performance of electric machines in electrified vehicles.
Implementation Method 1
a plurality of laminations each defining a plurality of poles arranged such that values of a pair of angles corresponding to each of the poles and defined between a magnetic axis of the pole and respective interpolar axes adjacent thereto are different
Data Source
AI summary
A rotor assembly has a rotor including a plurality of laminations each defining a plurality of poles arranged such that values of a pair of angles corresponding to each of the poles and defined between a magnetic axis of the pole and respective interpolar axes adjacent thereto are different. The values of the pairs define a repeating sequence around the lamination. The angles opposite an axis of rotation of the rotor are equal.