Segmented Rotor Sleeve for High-Speed Permanent Magnet Machines
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Solution Overview
Problem
Conventional internal permanent magnet machines face reduced power density and efficiency due to increased thickness of rotor bridges and center posts for higher speed applications, leading to higher magnet flux leakage and centrifugal loading limitations.
Innovation Solution
A rotor assembly with a sleeve component featuring axially extending radial land portions and radially extending disc portions, providing centrifugal stiffening and reducing weight, while maintaining structural integrity and magnetic flux path efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of rotor bridges and center posts is increased for higher speed applications, then the structural strength of the rotor is enhanced, but the magnet flux leakage increases significantly, reducing power density
Solution Approach 1:
The rotor structure is divided into multiple laminations with magnets embedded between them, rather than using a solid rotor body. This segmentation allows the magnetic flux to pass through the laminated structure with reduced leakage, while the individual laminations provide structural strength. The segmented design separates the structural support function (provided by the lamination framework) from the magnetic function (provided by the embedded magnets), resolving the contradiction between strength and power density.
Solution Approach 2:
The rotor employs a composite structure combining magnetic materials (for the magnets and magnetic circuits) with non-magnetic structural materials (for the laminations and mechanical support). This composite approach allows optimization of each material for its specific function - magnetic materials for flux conduction and non-magnetic materials for mechanical strength - thereby achieving both high structural strength and high power density without the flux leakage problems of conventional homogeneous rotor designs.
2Strength
If the thickness of bridges and center posts is increased to enhance structural strength, then the rotor can withstand higher speeds, but the overall weight increases, reducing power to weight ratio
Solution Approach 1:
The rotor is constructed from thin laminations stacked together, with each lamination being lightweight. The segmented lamination structure provides the necessary structural strength through the cumulative effect of multiple layers, rather than requiring a single thick heavy component. This segmentation enables the rotor to achieve high strength-to-weight ratio, allowing high-speed operation without excessive weight.
Solution Approach 2:
The structural thickness is optimized locally rather than uniformly throughout the rotor. The laminations are thin in regions where structural strength is sufficient, and thicker only where mechanically necessary. This localized optimization reduces overall rotor weight while maintaining adequate structural strength for high-speed applications, improving the power to weight ratio.
3Power
If permanent magnets are embedded in multiple laminations, then the machine achieves high power density, but the mechanical stresses concentrate in bridges and center posts, requiring increased thickness that reduces power density
Solution Approach 1:
The rotor is segmented into multiple laminations with magnets embedded between them, distributing the mechanical stresses across numerous interfaces rather than concentrating them in a few thick bridges and center posts. This segmentation of the lamination structure disperses the stress distribution, reducing peak stress concentrations while maintaining high power density through efficient use of magnetic materials.
Solution Approach 2:
The mechanical and magnetic parameters are optimized independently through the lamination structure. The lamination thickness, material properties, and stacking arrangement are adjusted to control mechanical stress distribution, while the magnet size, orientation, and positioning are optimized for magnetic performance. This independent parameter optimization allows high power density without excessive stress concentration in structural elements.
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
The solution enhances centrifugal load capacity, allowing for increased power density and improved electrical performance at higher speeds, while minimizing weight and cost, making the permanent magnet machine more efficient and suitable for high-speed applications.
Implementation Method 1
The maximum rotational speed of the rotor is dependent on the thickness of the Inconel sleeve and the mass of the permanent magnets. The speed at which the rotor can turn safely is limited by centrifugal loading on the permanent magnets and the overall weight
Implementation Method 2
The at least one rotor module is disposed about the rotor shaft and includes a plurality of permanent magnets. The magnetic field interacts with a stator winding to produce electricity in response to rotation of the at least one rotor module
Data Source
AI summary
A permanent magnet machine and a rotor assembly for the permanent magnet machine. The permanent magnet machine includes a stator assembly including a stator core including a stator winding to produce electrical currents. The stator assembly extending along a longitudinal axis with an inner surface defining a cavity. The rotor assembly including a rotor core and a rotor shaft. The rotor core is disposed inside the stator cavity and rotates about the longitudinal axis. The rotor assembly including a plurality of permanent magnets for generating a magnetic field which interacts with the stator winding to produce the electrical currents in response to rotation of the rotor assembly. within one or more cavities formed in a sleeve component. The sleeve component is configured to include a plurality of cavities or voids into which the permanent magnets are disposed to retain the permanent magnets therein and form an interior permanent magnet generator.