Asymmetrical Reluctance Rotor Cavities for Lower Torque Ripple
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Solution Overview
Problem
Reluctance motors suffer from low power factor due to phase-displacement between voltage and current, and torque ripple leading to noise and resonance, limiting their large-scale use.
Innovation Solution
Introduce asymmetries into the cavities of the rotor by alternating angular sectors with different geometries and fill these cavities with a polymer matrix containing magnetizable fillers, reducing torque ripple and increasing mean torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If asymmetries are introduced into the cavities of the rotor, then torque ripple is reduced and mean torque is increased, but device complexity increases
Solution Approach 1:
The patent applies asymmetry by introducing geometric variations in the rotor cavities, where at least one cavity has different dimensions or shape characteristics compared to others. This asymmetric configuration modifies the magnetic flux distribution and reduces torque ripple while maintaining structural feasibility through controlled geometric deviations from symmetry.
Solution Approach 2:
The patent implements local quality by applying different geometric characteristics to specific cavities rather than uniformly modifying all cavities. The asymmetric features are localized to particular rotor segments, allowing targeted optimization of torque characteristics in specific angular regions while preserving overall rotor balance and manufacturability.
2Power
If asymmetries are introduced into the cavities of the rotor, then mean torque is increased, but manufacturing complexity increases
Solution Approach 1:
The asymmetric cavity design achieves higher mean torque through optimized geometric configurations that enhance magnetic flux utilization. The patent balances manufacturing feasibility by limiting asymmetry to specific cavity parameters (such as radial depth or angular span) that can be accommodated by conventional machining and molding processes.
Solution Approach 2:
The patent employs parameter changes by systematically varying cavity geometric parameters (radius, depth, angular position) to optimize torque output. These parameter modifications are implemented within ranges that maintain compatibility with standard manufacturing tolerances and production methods, ensuring that torque enhancement does not come at the cost of excessive manufacturing complexity.
3Device complexity
If conventional symmetrical rotor design is used, then device complexity is low, but torque ripple and noise are high
Solution Approach 1:
The patent introduces controlled asymmetries in rotor cavity geometries to disrupt the periodic magnetic flux patterns that generate torque ripple and associated noise. By carefully designing asymmetric cavity configurations, the patent reduces resonant vibrations and acoustic emissions while maintaining relatively simple overall rotor architecture that does not substantially increase device complexity.
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 asymmetrical rotor design significantly reduces torque ripple and resonance while maintaining or enhancing torque, improving the power factor, and eliminating the need for rare earth permanent magnets, thus offering a cost-effective solution.
Implementation Method 1
Reluctance motors are motors which technologically date back to almost a century ago... Reluctance motors are characterized by a rotor structure which does not have windings and is magnetically anisotropic
Implementation Method 2
a filling material (16), in particular a polymer matrix with magnetizable fillers
Data Source
AI summary
A rotor (1) with N poles, wherein N is an even integer, wherein said rotor (1) is devoid of permanent magnets comprising rare earth elements and comprises a cylindrical body (2) and a filling material (16). The cylindrical body (2) extends along a body axis (X) and—in a plane perpendicular to the body axis (X)—delimits N adjacent angular sectors (4, 6). Each angular sector (4, 6) delimits cylindrical cavities (8, 12, 14, 8′, 12′, 14′) which have curvilinear cross-sections, where concave surfaces (18, 20, 22, 18′, 20′, 22′) of said cylindrical cavities (8, 12, 14, 8′, 12′, 14′) are directed in the opposite direction to the body axis (X). The filling material (16) fills at least partly the cylindrical cavities (8, 12, 14, 8′, 12′, 14′) and comprises or consists of a polymer matrix. At least one angular sector (6) delimits cylindrical cavities (8′, 12′, 14′) with a first geometry (type A) and at least one second angular sector (4) delimits cylindrical cavities (8, 12, 14) with a second geometry (type B) different from said first geometry. The first angular sector (6) is arranged angularly alternating with the second angular sector (4).