Rotor Magnet Segments With Edge Coercivity Against Demagnetization
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Solution Overview
Problem
Existing electric motors for machine tools experience efficiency losses and heating due to eddy currents in permanent magnets caused by cyclic magnetic field interactions, leading to irreversible demagnetization.
Innovation Solution
The rotor design incorporates permanent magnets with edge regions having a coercive field strength 5-15% higher than the central regions, and a remanent flux density 5-10% higher, with edge regions occupying 3-30% of the total volume, to mitigate demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If permanent magnets with uniform material properties are used in the rotor, then the manufacturing process is simple and cost-effective, but eddy currents occur in the permanent magnet causing efficiency losses and heating leading to irreversible demagnetization
Solution Approach 1:
The patent applies local quality by creating distinct material regions within the permanent magnet: edge regions with higher coercive field strength (5-15% higher) to resist demagnetization, and central regions with higher remanent flux density (5-10% higher) to maintain magnetic field strength. This non-uniform material distribution optimizes both reliability and performance by tailoring material properties to the specific functional requirements of each region.
2Reliability
If the volume of edge regions is increased to prevent demagnetization, then protection against irreversible demagnetization improves, but the remanent flux density in the magnet decreases
Solution Approach 1:
The patent employs parameter changes by carefully controlling the volume percentage of edge regions (3-30% of total magnet volume) and adjusting the coercive field strength (5-15% higher) and remanent flux density (5-10% higher) in different regions. This quantitative optimization balances the competing requirements of demagnetization protection and magnetic field strength maintenance through precise parameter specification.
3Reliability
If permanent magnets with higher coercive field strength are used throughout, then resistance to demagnetization improves, but the remanent flux density and torque production capability decrease
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the edge regions (3-30% volume) have higher coercive field strength (5-15% higher) specifically for demagnetization resistance, while the central regions maintain higher remanent flux density (5-10% higher) for optimal torque production. This spatial differentiation of material properties allows both requirements to be satisfied simultaneously in their respective locations.
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 solution reduces efficiency losses and prevents irreversible demagnetization by stabilizing the magnetic field, maintaining consistent torque and reducing operating temperatures.
Implementation Method 1
The magnetic field of the permanent magnets interacts with the magnetic field of the stator, which is generated by at least one electromagnet, in such a way that a torque is produced
Implementation Method 2
As a consequence, eddy currents occur in the permanent magnet, which, in addition to efficiency losses, generate additional heating in the rotor
Data Source
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AI summary
Rotor for an electric motor, in particular as a drive for a machine tool, wherein a rotor body is provided with at least one first and second permanent magnet arranged around an axis of rotation, wherein the material of each permanent magnet in a first and second edge region has a coercive field strength that is 5 to 15%, preferably 7 to 12%, higher than the material of each permanent magnet in the remaining regions outside the first and second edge region.