U-Shaped Ferrite Cores for Inductive Rotary Joints
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Solution Overview
Problem
Existing contactless rotary joints for transferring high electrical power, such as those used in CT scanners, face challenges with mechanical design complexity, weight, robustness, and reliability due to large centrifugal forces, and require significant mechanical support structures.
Innovation Solution
The design features a rotating power transformer with symmetrical, ring-shaped or disk-shaped parts using ferrite magnetic cores with significantly broader legs than the base for improved magnetic coupling, an elastic filler to compensate for thermal expansion, and a conductive shield to reduce stray flux and parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy iron or ferrite cores are used for guiding magnetic fields, then magnetic field guidance is improved, but weight and mechanical support structure requirements increase
Solution Approach 1:
The magnetic core is divided into multiple U-shaped ferrite core segments arranged in a circular pattern, replacing a single heavy core structure. Each segment independently guides magnetic flux, achieving effective magnetic field guidance while distributing weight and eliminating the need for massive mechanical support structures.
Solution Approach 2:
The patent uses ferrite material for the magnetic core segments, which provides high magnetic permeability and saturation flux density. This composite approach combines magnetic efficiency with reduced weight compared to traditional iron cores, resolving the contradiction between magnetic field guidance and weight.
2Area of stationary object
If large diameter rotary joint is designed, then free bore diameter requirement is met, but mechanical support structure complexity increases
Solution Approach 1:
The rotary joint is segmented into multiple identical U-shaped core units arranged circularly, allowing the system to achieve large diameter requirements without complex support structures. Each segment is a simple, identical unit that can be independently manufactured and assembled.
Solution Approach 2:
Each U-shaped ferrite core segment serves multiple functions: guiding magnetic flux, providing mechanical support, and defining the circular geometry. This multi-functionality eliminates the need for separate mechanical support structures, reducing overall device complexity while meeting large diameter requirements.
3Ease of manufacture
If standard U-shaped ferrite cores with equal leg and base cross-section are used, then manufacturing is simplified, but magnetic coupling and tolerance against displacement are reduced
Solution Approach 1:
The U-shaped ferrite core segments have non-uniform cross-sections with broader legs than base, concentrating magnetic flux where it is most needed for coupling. This local quality optimization enhances magnetic coupling and tolerance against displacement while maintaining manufacturability through precision grinding of the ferrite segments.
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 configuration enhances magnetic coupling, reduces losses and weight, increases tolerance against displacement, and minimizes external influences, resulting in a more robust and reliable power transfer with lower mechanical complexity.
Implementation Method 1
For guiding the magnetic fields between the primary and secondary side, a magnetic material, preferably a soft magnetic material is provided. Most preferably, the magnetic material is a ferrite material.
Implementation Method 2
A contactless rotary joint comprising an inductive power coupler is disclosed. Such a rotary joint is able to transfer power of more than hundred kilowatts from a stationary part to a rotating part.
Data Source
AI summary
A rotating power transformer comprises a primary magnetic core with a primary winding and a secondary magnetic core with a secondary winding. The magnetic cores preferably comprise a ferrite material and are U-shaped, and have a base connecting two legs. The width of the legs is significantly larger than the height of the base, resulting in a better magnetic coupling and a significantly improved tolerance to mechanical deviations.