Rotor Offset Bridge Inclination Reduces Stress Concentration
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Solution Overview
Problem
Existing rotor designs for rotating electrical machines face challenges in reducing the width of offset bridge portions while maintaining sufficient strength against centrifugal forces, which affects output torque due to increased magnetic flux leakage.
Innovation Solution
The rotor design incorporates a structure where the offset bridge is inclined in a cross-sectional direction orthogonal to the axial direction, approaching the magnetic pole centerline radially outward, and is positioned to align with the center of gravity of the surrounding hole group, reducing stress concentration and allowing for a narrower bridge width while maintaining strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the width of the offset bridge portion is reduced to improve output torque by minimizing magnetic flux leakage, then the output torque increases, but the strength of the rotor core against centrifugal force decreases
Solution Approach 1:
The offset bridge portion is designed with an asymmetric cross-sectional shape where the extending direction is inclined with respect to the magnetic pole center line, approaching the magnetic pole center line toward the outer side in the radial direction. This asymmetric configuration optimizes the distribution of centrifugal stress and magnetic flux, allowing the bridge to maintain sufficient structural strength while minimizing its width in the circumferential direction to reduce magnetic flux leakage and improve output torque.
2Power
If the width of the offset bridge portion is minimized to reduce magnetic flux leakage, then the output torque improves, but the stress concentration on the bridge increases
Solution Approach 1:
The extending direction parameter of the offset bridge is changed from being parallel to the magnetic pole center line to being inclined with respect to it, approaching the magnetic pole center line toward the outer side in the radial direction. This parameter change optimizes the stress distribution pattern, reducing stress concentration while maintaining minimal width for reduced magnetic flux leakage and improved output torque.
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 effectively mitigates stress concentration and reduces the width of the offset bridge portion, enhancing the rotor's ability to withstand centrifugal forces while maintaining necessary remanent flux density and utilizing reluctance torque.
Implementation Method 1
a rotor for a rotating electrical machine, which includes a rotor core and permanent magnets arranged in the rotor core
Implementation Method 2
it is necessary that the bridge portion such as an offset bridge portion be formed into such a size that the strength of a rotor core is a strength enough to resist a centrifugal force during rotation of the rotor
Data Source
AI summary
A rotor for a rotating electrical machine, the rotor including: a rotor core having a plurality of magnetic poles; and a plurality of permanent magnets arranged in the rotor core, wherein: in each of the plurality of magnetic poles, the rotor core has a plurality of holes including a first hole and a second hole in each of which a respective permanent magnet of the plurality of permanent magnets having a planar magnetic pole surface is arranged.