Permanent Magnet Rotor Bridge Geometry for Torque and Stress Balance
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Solution Overview
Problem
Permanent magnet rotors face a contradictory issue where thicker bridges alleviate centrifugal stress but increase leakage magnetic flux, reducing torque performance, while thinner bridges may not adequately support centrifugal force, leading to core deformation and bending stress.
Innovation Solution
A permanent magnet rotor design with a rotor core featuring first and second outer through holes and first and second inner through holes, where the outer opening angle is larger than the inner opening angle, and the inter-inner through hole length is greater than the inter-outer through hole length, to distribute stress effectively without compromising torque performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bridge is made thicker to support centrifugal force, then mechanical strength is improved, but leakage magnetic flux increases and torque performance deteriorates
Solution Approach 1:
The bridge structure is divided into multiple segments: a center bridge portion and multiple tip bridge portions. This segmentation allows each part to have optimized thickness - the center bridge can be thicker for strength while tip bridges are thinner to reduce leakage flux, resolving the contradiction between mechanical strength and torque performance
Solution Approach 2:
Different portions of the bridge have different thickness characteristics. The center bridge portion has greater thickness for structural support, while the tip bridge portions have reduced thickness to minimize magnetic flux leakage. This local differentiation of quality allows simultaneous optimization of strength and magnetic performance
2Power
If the bridge is made thinner to reduce leakage magnetic flux, then torque performance is improved, but mechanical strength decreases and core deformation increases
Solution Approach 1:
The bridge is segmented into center and tip portions with different thickness requirements. The center bridge maintains sufficient thickness for mechanical support while tip bridges are thinned for reduced leakage flux, achieving both torque improvement and adequate strength
Solution Approach 2:
The bridge structure exhibits asymmetric thickness distribution along its length, with the center portion being thicker and tip portions being thinner. This asymmetric design optimizes both mechanical support capability and magnetic flux characteristics simultaneously
3Power
If top bridges are removed to improve torque performance, then leakage magnetic flux is reduced, but centrifugal force support capability deteriorates
Solution Approach 1:
The top bridge structure is extracted/removed from the design, eliminating the associated leakage flux while the center bridge and tip bridge portions are retained and optimized to provide sufficient centrifugal force support capability
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 bending stress on the roots of bridges while maintaining or improving torque performance by optimizing the bridge geometry and support structure.
Implementation Method 1
permanent magnets arranged in a two-layered V-shape
Implementation Method 2
permanent magnet motor having permanent magnets arranged in a two-layered V-shape has been proposed and used
Implementation Method 3
bridges are provided to mechanically support centrifugal force acting on a core on the radially outer side of flux barriers and on permanent magnets
Data Source
AI summary
A permanent magnet rotor includes: a rotor shaft; a rotor core having, in each magnetic pole, a first and second outer through holes to make a pair and a first and second inner through holes to make a pair; and a first and second outer magnets, a first and second inner magnets housed in these respectively. An outer opening angle Θa between the first outer through hole and the second outer through hole is larger than an inner opening angle Θb between the first inner through hole and the second inner through hole. An inter-inner through hole length between the first inner through hole and the second inner through hole is larger than that between the first outer through hole and the second outer through hole.