Rotary Electric Machine Rotor with Segmented Ferrite Magnets
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Solution Overview
Problem
The increasing cost of rare earth magnets makes their use in electric vehicle rotors economically unviable, necessitating the use of ferrite magnets, which require larger volumes to achieve equivalent magnetic flux, posing a challenge in optimizing rotor design while maintaining efficiency and mechanical constraints.
Innovation Solution
A rotor design featuring a main magnet and auxiliary magnets arranged in a V-shaped configuration, with the auxiliary magnets occupying the intermediate space between the circumferential and central parts, optimizing the volume and magnetic flux while minimizing stator current and maintaining motor torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ferrite magnets are used instead of rare earth magnets, then manufacturing cost is reduced, but magnetic flux density decreases requiring larger magnet volume
Solution Approach 1:
The rotor magnetic system is segmented into main magnets and auxiliary magnets arranged in specific patterns (e.g., N-S-N or S-N-S sequences). This segmentation allows ferrite magnets with lower individual flux density to collectively generate sufficient total magnetic flux, resolving the contradiction between using cheaper ferrite material and maintaining required flux levels.
Solution Approach 2:
Multiple auxiliary magnets are merged with main magnets to form composite magnetic poles. The combined magnetic effect of these segmented ferrite magnets achieves flux density equivalent to or exceeding that of single rare earth magnets, while reducing overall manufacturing cost and enabling larger total magnet volume within the rotor.
2Quantity of substance
If magnet volume is increased to compensate for lower ferrite remanence, then magnetic flux is maintained, but rotor space for other components is reduced
Solution Approach 1:
Different regions of the rotor are assigned different magnetic pole configurations. Main magnets are positioned at optimal locations for flux generation, while auxiliary magnets are placed in intermediate regions to supplement flux without encroaching on space needed for rotor shaft, bearings, or cooling channels. This local optimization maintains flux while preserving essential rotor space.
Solution Approach 2:
The magnetic flux generation is extended from a single radial dimension to multiple dimensions by arranging magnets in axial sequences (N-S-N or S-N-S patterns). This multi-dimensional arrangement increases total flux volume without proportionally increasing the radial footprint, thereby maintaining flux levels while preserving rotor space for other components.
3Use of energy by moving object
If auxiliary magnets are added to optimize flux distribution, then stator current is minimized, but device complexity increases
Solution Approach 1:
The rotor employs asymmetric magnetic pole configurations where auxiliary magnets are strategically positioned only in specific angular or axial zones rather than uniformly distributed. This asymmetric arrangement optimizes flux distribution to minimize stator current while keeping the manufacturing and assembly process manageable by avoiding complete symmetry that would require identical complex patterns throughout.
Solution Approach 2:
Instead of distributing magnets uniformly or adding excessive numbers of auxiliary magnets throughout the entire rotor, the invention applies partial action by placing auxiliary magnets only in critical regions where flux supplementation is most beneficial. This selective placement achieves stator current minimization with moderate complexity increase, avoiding the excessive complexity that would result from comprehensive uniform distribution.
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 maximizes the magnetic flux and minimizes stator current, achieving efficient motor performance while reducing manufacturing costs by utilizing ferrite magnets, and can also be applied to rare earth magnets with reduced dysprosium levels.
Implementation Method 1
permanent magnets having a first radial plane of symmetry and the pole sections having a second radial plane of symmetry
Implementation Method 2
maximize the magnetic flux and minimizes stator current, achieving efficient motor performance
Data Source
Figure 1
Figure 2~3
AI summary
The rotor (1) according to the invention has a cylindrical overall shape and comprises a plurality of north poles (N) and south poles (S) which alternate and are formed from a plurality of permanent magnets (3, 4). The magnets are arranged in recesses (5, 6) extending along an axis (XX') of the rotor and are evenly distributed between a circumferential part (7) and a central part (6) of the magnetic mass (2) of the rotor so as to define a plurality of circumferential polar sections (10). According to the invention, each of the permanent magnets is made up of a main magnet (3) and of at least two auxiliary magnets (4) and the auxiliary magnets are arranged only between the circumferential part and an intermediate part (9) of the rotor extending between the circumferential part and the central part. According to one embodiment, the main magnet and the auxiliary magnets have substantially rectangular radial sections. Figure 1