Permanent-Magnet Rotor Pole Layout for Torque Ripple Reduction
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Solution Overview
Problem
Torque ripples in rotating electrical machines, particularly those with three-phase windings and buried magnets, negatively impact performance due to rotor skewing and flow leakage issues.
Innovation Solution
Introducing an angular offset parameter between successive polar angles or double polar angles, linked to the stator pitch, to compensate for rotor skewing and reduce torque ripples without increasing development time significantly, allowing for two-dimensional calculations and simulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If rotor skewing is applied to reduce torque ripples, then torque ripple is reduced, but flux leakage problems occur and performance deteriorates
Solution Approach 1:
The patent applies asymmetry by introducing an angular offset between the polar angles of successive poles, creating an asymmetric angular distribution pattern. This asymmetric configuration disrupts the periodicity of the magnetic field harmonics that cause torque ripples, while maintaining proper flux linkage. The angular offset parameter δ creates deliberate asymmetry in the pole angular positions, which transforms the harmonic content of the back-EMF and reduces the amplitude of torque-fluctuating components without causing flux leakage.
Solution Approach 2:
The patent changes the angular parameter distribution of the rotor poles by introducing an offset parameter δ. Instead of uniform angular spacing, the polar angles are modified according to the offset pattern, which changes the spatial harmonic distribution of the magnetic field. This parameter change approach allows optimization of torque ripple reduction while maintaining flux linkage efficiency, as the angular offset can be tuned to target specific harmonic orders responsible for torque ripples.
2Object-generated harmful factors
If complex rotor configurations are used to reduce torque ripples, then torque ripple is reduced, but development time increases
Solution Approach 1:
The patent modifies existing rotor design parameters (angular positions of poles) rather than introducing fundamentally new structural elements. This parameter-based approach allows for straightforward calculation and simulation using standard two-dimensional tools, avoiding the need for complex three-dimensional modeling or experimental prototyping. The angular offset parameter can be directly incorporated into conventional design software, significantly reducing development time compared to geometric modifications.
Solution Approach 2:
The patent maintains the conventional rotor structural framework and simply superimposes an angular offset pattern on the existing pole configuration. This copying approach preserves the proven structural design while adding a computational parameter layer that reduces torque ripple. The base rotor geometry remains unchanged, allowing direct reuse of existing manufacturing templates and assembly procedures, thereby minimizing development time.
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
Significantly reduces torque ripples and total harmonic distortions, improving the machine's performance and regularizing no-load voltage, with notable gains from an angular offset parameter between 0.5 and 1.5 times the stator pitch.
Implementation Method 1
a stator comprising a body provided with teeth delimiting notches and a winding housed in the notches of the stator body, a rotor comprising a body and poles formed by permanent magnets
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
The invention pertains primarily to a rotary electric machine, in particular for a motor vehicle, including: - a stator comprising a body provided with teeth delimiting slots and a winding that is housed in the slots of the stator body; - a rotor (12) comprising a body (21) and poles (22) that are formed by permanent magnets (23), characterized in that - two successive polar angles, each corresponding to a circumferential extent of a pole (22), or - two successive dual polar angles (A0-A4), each corresponding to a circumferential extent of two adjacent poles (22), - exhibit an angular difference in relation to one another that is dependent on an angular offset parameter (δ) related to a stator pitch.