Ferromagnetic Shielding Sleeve for Power Cable Loss Reduction
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Solution Overview
Problem
Existing magnetic shielding solutions for three-phase power cables, such as steel tubes and boxes, face challenges including high eddy current and hysteresis losses, limited flexibility, high costs, and corrosion issues, which reduce current-carrying capacity and increase operational expenses.
Innovation Solution
A magnetic shielding system using a ferromagnetic shielding sleeve or box combined with highly permeable foils or sheets, allowing gaps in the shielding construction to reduce magnetic resistance and losses, while maintaining effective shielding, and utilizing corrosion-resistant materials and designs to address mechanical and cost challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steel tubes or boxes are used for magnetic shielding, then shielding effectiveness is improved, but eddy current and hysteresis losses increase significantly
Solution Approach 1:
The patent combines steel tubes or boxes with highly permeable ferromagnetic foils or sheets to create a composite shielding structure. The steel provides mechanical strength and basic shielding, while the highly permeable material enhances magnetic field diversion with lower losses. This composite approach maintains shielding effectiveness while reducing eddy current and hysteresis losses compared to solid steel construction.
Solution Approach 2:
The highly permeable ferromagnetic foils or sheets are applied selectively to specific areas of the steel tube or box, particularly on the inner surface facing the cables. This localized application provides enhanced shielding where it is most needed while minimizing the total amount of material and associated losses throughout the entire structure.
2Strength
If large wall thickness is used for steel shielding, then mechanical strength and corrosion resistance are improved, but weight and cost increase
Solution Approach 1:
The steel tube or box provides the mechanical strength and corrosion resistance framework, while the thin highly permeable ferromagnetic foils or sheets add shielding functionality. This composite structure achieves the required mechanical properties and shielding effectiveness without the excessive weight that would result from using thick steel alone for both structural and shielding purposes.
Solution Approach 2:
The highly permeable ferromagnetic foils or sheets are thin film materials that provide enhanced magnetic shielding functionality. These thin films are applied to the steel structure, adding shielding capability without significant weight increase, while the underlying steel tube or box maintains the mechanical strength and corrosion resistance.
3Area of stationary object
If steel tube diameter is reduced to achieve small center distances, then space utilization is improved, but eddy current losses increase extremely
Solution Approach 1:
The highly permeable ferromagnetic foils or sheets applied to the inner surface of the steel tube create a low-reluctance path for magnetic flux close to the cables. This reduces the magnetic field strength in the gaps between cables, allowing smaller center distances without proportionally increasing eddy current losses in the steel tube wall.
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 approach significantly reduces losses in the shielding system, increases cable load capacity, and lowers system costs by minimizing the required steel thickness and weight, while maintaining high shielding effectiveness.
Implementation Method 1
The closed ferromagnetic wall of the steel pipe magnetically short-circuits a large part of the magnetic field lines that would otherwise run outside, offering them a 'magnetically highly conductive' parallel path due to the high relative permeability of the steel
Implementation Method 2
highly permeable material, for example a commercially available steel tube
Implementation Method 3
the eddy current and reversal losses in the steel pipe increase extremely
Implementation Method 4
eddy current and reversal losses
Implementation Method 5
offering them a 'magnetically highly conductive' parallel path
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The arrangement has cable wires (10) attached to a plastic tube (14) and forming a phase conductor. The cables wires are surrounded by a shielding casing (15), where the casing is designed in a tube or box-shape and divided into individual elements in a longitudinal direction. Shielding foils (20) made from high-permeable material is arranged between the cable wires and the casing, and have gaps, such that the cable wires are surrounded by the casing only in a surface area of 70 to 95 percentages. A layer of electrically conductive material is attached to the shielding foils. An independent claim is also included for a method for forming a magnetic field shielding of an alternating current-power cable.