Segmented Ferrite Magnets in IPM Rotor Design
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Solution Overview
Problem
Traditional interior permanent magnet (IPM) rotors are costly and time-consuming to manufacture due to complex magnet geometries and tight tolerances, and they require expensive magnet materials, which limits their efficiency and cost-effectiveness.
Innovation Solution
A rotor design using equal-sized segmented ferrite magnets arranged in layers with air gaps adjacent to the magnets, replacing complex magnet geometries with rectangular magnets that are easier and cheaper to produce, and allowing for simpler tooling and reduced mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional IPM rotor designs with complex magnet geometries are used, then magnetic performance is improved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The rotor magnets are divided into multiple segments within each slot, with air gaps between segments. This segmentation allows using simple rectangular ferrite magnet shapes while maintaining the magnetic performance through proper arrangement of multiple segments, resolving the contradiction between complex geometry and manufacturing simplicity.
Solution Approach 2:
Different regions of the rotor slot are utilized with segmented magnets arranged to create specific local magnetic field characteristics. The air gaps between segments are strategically positioned to achieve desired flux distribution, maintaining magnetic performance without requiring complex overall magnet geometries.
2Reliability
If expensive NdFeB magnet material is used, then magnetic performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive NdFeB magnets with cheaper ferrite magnets. While individual ferrite magnets have lower magnetic strength, the segmented arrangement with multiple magnets per slot compensates for this, achieving comparable overall magnetic performance at reduced material cost.
Solution Approach 2:
The invention changes the magnetic material parameter from high-performance NdFeB to cost-effective ferrite, and compensates by changing the arrangement parameter (segmentation into multiple smaller magnets per slot). This parameter substitution maintains functional performance while reducing cost.
3Reliability
If tight manufacturing tolerances are required for complex magnet geometries, then magnetic performance is improved, but manufacturing time and cost increase
Solution Approach 1:
By segmenting the magnets into multiple simpler rectangular pieces per slot, the manufacturing precision requirements for each individual magnet are relaxed. Standard rectangular ferrite magnets with conventional tolerances can be used instead of complex single-piece magnets requiring tight tolerances.
Solution Approach 2:
Multiple identical segmented magnet copies are placed in each slot. This allows using standardized, easily manufactured rectangular magnet copies rather than custom-shaped magnets, significantly reducing manufacturing precision requirements while maintaining performance through proper replication and arrangement.
4Reliability
If rotor slots are designed to accommodate complex magnet geometries, then magnetic performance is improved, but ease of manufacture decreases
Solution Approach 1:
The rotor slots are designed to accommodate multiple segmented rectangular magnets with air gaps, rather than single complex-shaped magnets. This simplifies slot fabrication to standard rectangular cross-sections, making the slots easier to manufacture while maintaining magnetic performance through the segmented arrangement.
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 design reduces manufacturing costs, maintains magnetic performance, and allows for higher rotor speeds and increased magnet usage, while using less expensive ferrite magnets to achieve comparable efficiency to more expensive NdFeB magnets.
Implementation Method 1
The rotor field in a permanent magnet machine is obtained by virtue of its structure
Implementation Method 2
permanent magnet machines exhibit superior efficiency as compared to other such machines
Implementation Method 3
These rotor layers act as barriers to the permanent magnet field of the lower primary magnet layer, reducing the air-gap magnet flux
Data Source
AI summary
An internal permanent magnet machine (“IPM machine”) of the type used, for example, with traction motors and hybrid electric vehicles, includes a rotor having a plurality of equal-sized (e.g., rectilinear) segmented ferrite magnets arranged in one or more layers. The magnets are inserted within rotor slots that are larger than the magnets themselves, such that one or more air gaps are formed adjacent to the magnets in each layer.