Asymmetric Pole Arc Angles for Torque Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Interior permanent magnet machines experience torque ripple due to harmonic flux components, leading to motor torque fluctuations, vibration, and reduced efficiency, which conventional skewing methods cannot fully eliminate without reducing average torque and increasing manufacturing complexity.
Innovation Solution
The solution involves radial skewing of rotor magnets by offsetting the magnetic axis of one pole with respect to the adjacent pole and varying the pole arc angles between adjacent magnets or magnet sets, breaking the symmetry of rotor laminations to minimize torque ripple while maintaining average torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional skewing methods are used to reduce torque ripple, then torque ripple is reduced, but average torque is reduced and manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by varying the pole arc angles of different rotor magnets rather than using uniform angles. Specifically, first rotor magnets have a first pole arc angle while second rotor magnets have a second pole arc angle that differs from the first. This localized variation in geometric parameters reduces torque ripple by canceling harmonic flux components while maintaining overall average torque, avoiding the power loss associated with conventional skewing methods.
Solution Approach 2:
The patent employs parameter changes by modifying the pole arc angle parameter of rotor magnets to different values. The first pole arc angle and second pole arc angle are specifically chosen to reduce particular harmonic orders in the torque ripple spectrum. This parameter optimization allows torque ripple reduction without the need for axial skewing that would reduce average torque output.
2Object-generated harmful factors
If conventional skewing methods are used to reduce torque ripple, then torque ripple is reduced, but device complexity increases
Solution Approach 1:
The patent simplifies manufacturing by applying local quality variations only to the magnet geometry (pole arc angles) rather than requiring complex axial skewing of the entire rotor structure. The different pole arc angles can be directly formed during magnet manufacturing or assembly, avoiding the need for precision skewing operations and reducing overall device complexity while still achieving torque ripple reduction.
Solution Approach 2:
The patent introduces controlled asymmetry by using different pole arc angles for different rotor magnets. This asymmetric geometric configuration breaks the symmetry that causes certain harmonic components in the flux distribution, thereby reducing torque ripple. The asymmetric design is simpler to manufacture than axial skewing because it involves only geometric parameter variations rather than structural misalignments.
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 approach significantly reduces torque ripple amplitude while maintaining average torque, improving motor efficiency and simplifying manufacturing processes by eliminating the need for complex skewing techniques.
Implementation Method 1
The interaction of an electromagnetic flux flow path created by the stator windings with the flux flow path created by the permanent magnets typically is accompanied by harmonic waveform components that induce motor torque fluctuations
Implementation Method 2
a stator with a ferrous metal core comprising stacked laminations
Data Source
AI summary
An internal permanent magnet machine has multiple rotor sections, each section having multiple rotor laminations. Permanent magnets are placed asymmetrically in lamination openings to attenuate oscillations in torque caused by harmonic components of magnetic flux. Asymmetry is achieved by placing adjacent permanent magnets or magnet sets on the rotor periphery with different rotor magnetic pole arc angles.