Embedded Permanent Magnet Rotor Cavities Reduce Centrifugal Load
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Solution Overview
Problem
The existing permanent magnet embedded rotor designs face issues with high centrifugal load on the bridge portion between adjacent permanent magnets, leading to potential demagnetization and reduced torque production due to excessive magnetic flux short-circuiting.
Innovation Solution
The design incorporates a rotor core with strategically placed cavities and recesses that reduce the size of the core zone, thereby decreasing the centrifugal load on the bridge portion and preventing demagnetization, while also increasing reluctance torque through optimized cavity formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the core zone is increased to increase magnet torque, then torque production is improved, but centrifugal load on the bridge portion becomes excessively high
Solution Approach 1:
The invention divides the rotor core structure into distinct segments: magnet accommodating portions, bridge portions, and core zones. By segmenting the core zone and positioning it between the bridge portions rather than allowing it to extend to the rotor outer circumferential surface, the design reduces the centrifugal load path while preserving the torque-generating magnetic flux paths. This segmentation allows the core zone to be smaller and not bear excessive centrifugal forces.
Solution Approach 2:
The invention extracts the core zone from direct contact with the rotor outer circumferential surface by introducing bridge portions as intermediaries. The core zone is taken out from the high-stress region near the outer surface and repositioned in a lower-stress region between the bridge portions, thereby reducing centrifugal load while maintaining magnetic flux continuity for torque production.
2Power
If permanent magnets are arranged in V shape to increase core zone, then magnet torque is increased, but bridge portion becomes the sole support leading to high centrifugal load
Solution Approach 1:
The invention applies local quality by giving different functional characteristics to different regions: the bridge portions are designed with sufficient strength to support centrifugal loads, while the core zones are positioned in regions with lower centrifugal stress. The magnet accommodating portions are optimized for magnetic flux, and the bridge portions are optimized for mechanical support, creating a differentiated structural quality that resolves the contradiction.
3Power
If cavities are made to open through rotor outer circumferential surface to reduce short-circuited magnetic flux, then torque is improved, but core zone size increases centrifugal load
Solution Approach 1:
The invention resolves the contradiction by changing the dimensional arrangement of the cavities. Instead of allowing cavities to extend radially to the rotor outer circumferential surface (one-dimensional radial extension), the cavities are positioned in the axial and circumferential dimensions between the bridge portions. This dimensional repositioning allows cavities to block short-circuited magnetic flux paths while avoiding the high-centrifugal-load region at the outer surface.
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 effectively reduces the centrifugal load on the bridge portion, enhances torque production, and prevents demagnetization by distributing the load more evenly and increasing the reluctance torque.
Implementation Method 1
The permanent magnets form a plurality of magnetic poles. Each adjacent pair of the magnetic poles is different from one another. Thus, the magnetic fluxes are likely to be short-circuited between the ends of each adjacent pair of the permanent magnets.
Implementation Method 2
A rotor core for a permanent magnet embedded rotor includes a plurality of embedded permanent magnets. The permanent magnets form a plurality of magnetic poles.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
An accommodating recess (21 A, 21 B) has a magnet accommodating portion (19A, 19B) for accommodating a permanent magnet (17A, 17B) and a cavity (20A, 20B), which is located at the q-axis side of the magnet accommodating portion (19A, 19B). The cavity (20A, 20B) opens through a rotor outer circumferential surface (162). A starting point (Pa1, Pb1) of an outer cavity forming surface (201A, 201 B) is located on the rotor outer circumferential surface (162). The outer cavity forming surface (201A, 201 B) intersects either a magnetic pole surface (170A, 170B) or an imaginary extended plane (23A, 23B) of a magnetic pole facing surface (191A, 191 B). The rotor outer circumferential surface (162) includes portions of an imaginary annular line (E). A starting point (Pa1, Pb1) of the outer cavity forming surface (201A, 201 B) is located between the d-axis and an intersection point (Qa, Qb) between the imaginary annular line (E) and the imaginary extended plane (23A, 23B) of the magnetic pole facing surface (191A, 191 B).