Toroidal Magnetic Bearing for Small-Diameter Rotor Stability
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Solution Overview
Problem
Existing magnetic bearing devices are not optimally suited for small-diameter rotors due to high magnetic reluctance and the need for large windings, which increases cost and size, and are often complex in design, limiting their applicability.
Innovation Solution
A compact magnetic bearing device with a stator featuring a closed, toroidal magnetic core and radial bearing windings arranged in a toroidal configuration, interacting with an axially magnetized permanent magnet to generate radial bearing forces, and optionally including axial bearing windings and magnetic guide rings to enhance force generation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional slotted stator design with radially extending teeth is used, then radial bearing forces can be generated, but the air gap becomes comparatively large in relation to rotor diameter, leading to high magnetic reluctance and requiring large windings
Solution Approach 1:
The stator core is segmented into multiple radially extending teeth that are magnetically coupled through yokes, creating multiple parallel magnetic circuits. This segmentation allows the magnetic flux to be distributed across multiple paths, reducing the reluctance of each individual path and enabling the use of smaller windings while maintaining sufficient bearing forces.
Solution Approach 2:
The patent introduces axial magnetization of permanent magnets in the rotor, adding an axial dimension to the magnetic field generation. This axial component interacts with radially oriented stator windings to produce radial bearing forces, effectively utilizing three-dimensional magnetic field interactions to overcome the limitations of traditional two-dimensional radial magnetization designs.
2Force
If traditional slotted stator design is used, then radial bearing forces can be generated, but the device size and cost increase due to large windings required for small-diameter rotors
Solution Approach 1:
The patent changes the magnetization direction parameter of the permanent magnets from radial to axial orientation. This parameter change fundamentally alters the magnetic circuit configuration, enabling more efficient flux paths that reduce the volume of magnetic materials and windings required, thereby decreasing the overall stator volume while maintaining bearing force capability.
Solution Approach 2:
The stator assembly comprises composite structures combining magnetically soft core materials with precisely positioned permanent magnets and windings. This composite approach optimizes the magnetic properties of each component to work synergistically, reducing the total volume required while achieving the necessary bearing forces through enhanced magnetic flux density and distribution.
3Force
If homopolar part with axial bearing windings is added, then axial bearing forces are generated, but the device requires considerable space and the bearing forces are rather limited
Solution Approach 1:
The radial bearing windings are designed to serve dual functions: generating radial bearing forces through interaction with radially magnetized permanent magnets, and generating axial bearing forces through interaction with axially magnetized permanent magnets. This multi-functionality eliminates the need for separate axial bearing windings, reducing device volume while providing both radial and axial support capabilities.
Solution Approach 2:
The patent merges the radial and axial bearing force generation functions into a single integrated stator structure with unified windings. By combining these functions, the design eliminates redundant components and reduces overall device volume while maintaining the capability to generate both radial and axial bearing forces through coordinated control of the same winding system.
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 design achieves a compact, cost-efficient solution for controlling radial displacements of small-diameter rotors with strong radial bearing forces, while maintaining stability against axial and tilt displacements, thus addressing the limitations of previous designs.
Implementation Method 1
at least one radial bearing winding arranged on the at least one closed magnetic core in a toroidal configuration, the at least one radial bearing winding being arranged to interact with a radial component of a permanent magnetic field generated by the at least one axially magnetized permanent magnet to obtain a radial bearing force
Data Source
Figure 1~3
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Figure 7~8
AI summary
A magnetic bearing device comprises a stator (30) and a rotor (10) supported in the stator for rotation around a rotation axis (R). The rotor comprises at least one permanent magnet (21, 22) that is magnetized along the rotation axis. The stator comprises at least one closed magnetic core (31) that surrounds the rotor (10) and at least one radial bearing winding (32) arranged on the closed magnetic core (31) in a toroidal configuration. The at least one radial bearing winding is arranged to interact with a permanent magnetic field generated by the at least one permanent magnet to obtain a radial bearing force when current is supplied to the at least one radial bearing winding.