Outer Rotor IPM Motor Cavities for Torque Density
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Solution Overview
Problem
Internal permanent magnet motors with outer rotor configurations face challenges in achieving high torque density and extended speed range while maintaining compact size, as they often require expensive materials and complex manufacturing processes, limiting their cost-effectiveness and performance in vehicular applications.
Innovation Solution
The design incorporates a rotor with magnetically permeable substrate material, featuring proximal and distal cavities that hinder magnetic flux leakage, and a stator with windings, allowing for efficient torque generation and reduced material usage, thereby optimizing magnetic flux concentration and minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high fill-factor motors are used to achieve higher torque and efficiency, then torque density improves, but cost and manufacturing complexity increase
Solution Approach 1:
The rotor pole is segmented into multiple magnet segments (first magnet, second magnet, third magnet) arranged in series along the flux path. This segmentation allows for more efficient magnetic flux utilization and higher torque density while using standard manufacturing techniques for each segment, avoiding the need for complex high-fill-factor winding processes
Solution Approach 2:
The invention introduces proximal cavities and distal cavities at specific locations within the rotor pole to concentrate magnetic flux where it is most effective. The proximal cavity concentrates flux near the stator interface, while the distal cavity concentrates flux at the far end of the magnet segments. This localized flux concentration achieves high torque density without requiring uniformly complex structures throughout the motor
2Volume of moving object
If motor size is reduced for vehicle applications, then compactness improves, but starting torque decreases
Solution Approach 1:
The invention changes the magnetic circuit parameters by introducing proximal cavities and distal cavities that alter the flux distribution within the rotor pole. These cavities create regions of concentrated flux that increase the effective magnetic coupling between the rotor and stator, enabling higher torque density in a compact volume. The series arrangement of multiple magnet segments also changes the effective magnetic path length and flux density parameters
Solution Approach 2:
The rotor pole uses a composite structure combining multiple magnet materials (different magnet segments) with a magnetically permeable substrate material. This composite approach allows optimization of each component's properties - the magnet segments provide the magnetic field while the substrate provides structural support and flux guidance - achieving high torque in a compact package without requiring expensive high-performance materials throughout the entire motor
3Productivity
If expensive high-performance materials are used to increase torque, then torque density improves, but cost increases
Solution Approach 1:
The invention extracts the critical flux-concentration function from expensive high-performance materials and implements it through geometric features (proximal cavities and distal cavities) in the magnetic circuit. This allows standard magnet materials to achieve high torque density through optimized flux paths rather than relying on expensive materials, significantly reducing material costs while maintaining high torque output
Solution Approach 2:
The invention uses standard, cost-effective magnet materials arranged in a series configuration with optimized magnetic circuit features instead of expensive high-performance magnets. The multiple standard magnet segments in series provide cumulative magnetic effect equivalent to or exceeding expensive single-piece high-performance magnets, achieving high torque density with cheaper materials
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 configuration enhances torque density and extends the speed range of internal permanent magnet motors, improving performance while reducing material costs and manufacturing complexity, making them more suitable for vehicular applications.
Implementation Method 1
Each rotor pole can comprise: a substrate comprising a magnetically permeable substrate material
Implementation Method 2
The first proximal cavity and the second proximal cavity can be configured to hinder leakage of magnetic flux into one or more of the plurality of stator poles from a region of the substrate joining adjacent rotor poles
Implementation Method 3
Each of the plurality of rotor poles can further comprise at least one of: a first distal cavity in the substrate, the first distal cavity extending from the respective distal end of the first magnet
Data Source
AI summary
Provided is an electric motor comprising: a stator comprising stator poles arranged radially and a rotor comprising rotor poles, each comprising: a substrate comprising a magnetically permeable material and at least a first magnet and a second magnet. The magnets can comprise a respective proximal end proximal to the stator and a respective distal end opposite the respective proximal end, and distal from the stator. A distance between respective proximal ends of the magnets can be equal to or greater than a distance between respective distal ends of the magnets. Each rotor pole also comprise first and second proximal cavities, each cavity extending from the respective proximal end of a magnet for a given length along about the circumferential direction and away from the proximal end of the other magnet. Sum of the lengths of the proximal cavities can be about equal to a width of each stator pole.