Lobed Ferrite Rotor Pole Geometry for Torque Optimization
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Solution Overview
Problem
The increasing cost of rare-earth magnets makes their use in electric machine rotors for automotive applications economically unviable, necessitating the replacement with ferrite magnets, which result in lower performance due to lower remanence, requiring optimization of magnetic pole shapes to maintain torque and efficiency.
Innovation Solution
The rotor design features alternating North and South poles with permanent magnets in polygonal radial sections and lobes that maximize radial magnetic flux and minimize leakage flux, with a specific overlap angle and ratio to optimize magnetic flux distribution, and includes non-magnetic tie rods and axial grooves to control the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ferrite magnets are used to replace rare-earth magnets, then manufacturing cost is reduced, but magnetic flux and torque performance deteriorate
Solution Approach 1:
The patent changes the geometric parameters of the magnetic poles by introducing lobes with specific overlap angles (30-60 degrees) and overlap ratios (0.35-0.50). This parameter optimization compensates for the lower remanence of ferrite magnets, maximizing the useful magnetic flux in the air gap and maintaining torque performance comparable to rare-earth magnet machines while using cost-effective ferrite materials.
Solution Approach 2:
The patent applies local quality optimization by creating lobed pole sections with specific geometric features (lobes having predetermined overlap angles) in critical areas where magnetic flux concentration is needed. This localized geometric modification enhances the magnetic flux density in the air gap at specific positions, compensating for the inherently lower magnetic strength of ferrite magnets without requiring expensive rare-earth materials throughout the entire rotor.
2Ease of manufacture
If ferrite magnets are used to replace rare-earth magnets, then manufacturing cost is reduced, but useful magnetic flux deteriorates
Solution Approach 1:
The patent optimizes geometric parameters including the overlap angle (30-60 degrees) and overlap ratio (0.35-0.50) of the lobed pole sections. These parameter changes are specifically designed to maximize the useful magnetic flux circulating radially in the pole sections, compensating for the lower remanence of ferrite magnets and achieving flux levels comparable to rare-earth magnet machines.
Solution Approach 2:
The patent introduces a new geometric dimension by adding lobes to the pole sections, creating a three-dimensional magnetic flux path optimization. The lobes extend in the circumferential direction with specific overlap, creating additional flux paths and concentrating magnetic flux in the air gap, thereby increasing the useful magnetic flux despite using lower-performance ferrite magnets.
3Quantity of substance
If lobes with overlap are added to pole sections, then useful magnetic flux is maximized, but device complexity increases
Solution Approach 1:
The patent segments the pole sections into distinct lobed regions with predetermined overlap angles. Each lobe is a separate geometric entity that can be independently defined and manufactured. This segmentation allows for systematic optimization of magnetic flux distribution while maintaining a modular structure that can be produced using conventional manufacturing techniques, balancing complexity with performance benefits.
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 enhances the magnetic flux and torque of ferrite magnet-based rotors to match rare-earth magnet performance, reducing the intensity of the stator magnetic field and copper mass, thereby lowering manufacturing costs and maintaining performance.
Implementation Method 1
The rotor comprises a plurality of permanent magnets (3) arranged in first recesses (4) extending along an axis (X-X') of the rotor and regularly distributed between a circumferential part (5) and a central part (6) of a magnetic mass (2) so as to define a plurality of circumferential pole sections (7) having a predetermined pole pitch. The permanent magnets of the rotor type in question have a first polygonal radial section and a first axial plane of symmetry.
Implementation Method 2
these pole sections (7) having a second radial section forming a lobe (8) on the outside and a second axial plane of symmetry. The rotor (1) according to the invention is remarkable in that this lobe (8) partially covers the permanent magnets (3) so as to maximize a useful magnetic flux circulating radially in each of the pole sections (7) and to minimize a leakage magnetic flux circulating in a circumferential direction in the circumferential part (5) of the rotor (1).
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A rotor (1) comprising a plurality of alternating magnetic poles formed by permanent magnets (3) distributed regularly between a circumferential portion (5) and a central portion (6) of the magnetic body (2) of the rotor and defining circumferential pole sections (7). The pole sections have a pre-determined pole pitch (Thetarho) and comprise a lobe-forming radial section (8). The lobe-forming radial section partially covers the magnets, such as to maximize a useful magnetic flux (PhiU) flowing radially through each of the pole sections and to minimize a leakage magnetic flux flowing through the circumferential portion. The pole sections can have a pre-determined pole overlap angle (Thetar) such as to maximize the useful magnetic flux (PhiU) and to minimize the leakage magnetic flux (PhiL), said overlap angle (Thetar) being a viewing angle of the lobe (8) from a point on the axis of the rotor.