Rectangular Coil Element Geometry for Stable Current-Sensor Winding
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Solution Overview
Problem
Current coil elements for current sensing devices face challenges due to imperfections in the winding body, such as steps and flash/burrs from injection molding, which affect wire tension and lead to instability and breakage, especially in constrained spaces with non-circular winding contours.
Innovation Solution
A coil element with a winding body having a specifically designed rectangular cross-section with controlled radii at corners and inner regions, maximizing the winding contour area to maintain consistent wire tension and reduce stress, allowing for high-speed and accurate winding with minimal manufacturing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a rectangular winding contour is used to maximize space utilization, then space efficiency is improved, but wire tension stability deteriorates due to corner effects
Solution Approach 1:
The winding body incorporates different radius values at different locations: smaller radius rc at corner regions and larger radius ra at inner regions of straight sides. This local variation in geometry allows the winding contour to maintain a rectangular shape for space efficiency while creating tension-stabilizing effects at critical corner locations where wire tension variations are most problematic.
2Reliability
If the winding body is free of molding imperfections, then wire tension stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent accepts that injection molding imperfections (steps, flash/burrs) will exist but designs the winding body geometry with specific radius variations that compensate for these defects. The controlled imperfections in the molding process are converted into a beneficial design feature where the radius variations at corners and straight sections work together to stabilize wire tension despite the presence of manufacturing defects.
3Manufacturing precision
If wire tension is increased during winding, then winding quality is improved, but wire breakage risk increases due to tension peaks at corners
Solution Approach 1:
The winding body geometry parameters (radius rc at corners, radius ra at inner regions) are specifically designed to modify the distribution of wire tension during winding. By changing the geometric parameters of the winding contour, the system achieves stable wire contact and winding quality without creating excessive tension peaks that would lead to wire breakage.
Data Source
AI summary
A coil element includes a winding body and a length of wire wound around the outer surface of the winding body. A cross section of the outer surface perpendicular to the axis of the winding body has a substantially rectangular shape. A first axis of the cross section is equally spaced from the two first sides and has a dimension, a, and a second axis of the cross section perpendicular to the first axis of the cross section is equally spaced from the two second sides and has a dimension, b. The cross section has a first radius rc, a second radius ra, a third radius rb, and a fourth radius rao; wherein a≥b; rc<ra<∞; rc<rb<∞; ra<ra0; rb<ra0.