Rogowski Coil Gap Compensation via Planar Spiral Winding
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Solution Overview
Problem
Rogowski coils, used for current measurement, do not physically recreate the theoretical closed loop due to a physical gap between the ends of the flexible member, leading to measurement errors.
Innovation Solution
A planar spiral compensation winding is used, where the conductor winds around a fixed point with varying distances, forming a spiral around the central axis of the Rogowski coil to compensate for the gap, located between the ends of the flexible member to form a contiguous loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a physical gap is left between the ends of the flexible member in the Rogowski coil, then the coil remains flexible and easy to install, but the theoretical closed loop is not physically recreated leading to measurement errors
Solution Approach 1:
A compensation winding is introduced as an intermediary element between the first and second ends of the flexible member. This compensation winding acts as a mediator that creates the necessary magnetic flux linkage to compensate for the physical gap, thereby maintaining measurement accuracy while preserving the flexibility and ease of installation of the Rogowski coil.
2Measurement precision
If cylindrical compensation windings are used to compensate for the gap, then measurement accuracy is improved, but production complexity and cost increase
Solution Approach 1:
The compensation winding is segmented into discrete turns that can be independently formed and assembled. This segmentation allows for simpler production processes compared to continuous cylindrical windings, reducing manufacturing complexity while maintaining the compensation effect. The segmented structure enables easier integration with the flexible member and simplifies quality control.
3Measurement precision
If the compensation winding is tightly wound to maximize compensation effect, then measurement accuracy improves, but the flexibility of the coil is reduced
Solution Approach 1:
The compensation winding is designed with varying local characteristics - the winding density and spacing are optimized locally to provide maximum compensation effect where needed while maintaining overall flexibility. The winding structure is locally adapted to balance between compensation effectiveness and flexibility, allowing the coil to remain easily installable while achieving accurate measurements.
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 effectively compensates for the gap, reducing measurement errors and improving accuracy, while being more cost-effective and reliable compared to prior cylindrical compensation methods by simplifying production processes and reducing the risk of inaccuracies.
Implementation Method 1
The compensation means comprises a conductor in which the conductor is arranged to wind around a fixed point... the conductor is arranged to wind around a fixed point and wherein the distance from a first point on the conductor to the fixed point is greater than the distance from a second point on the conductor to the fixed point
Data Source
AI summary
Current testing/measuring apparatus 10 comprises a flexible member 12 having a first end 14 and a second end 16. In use, the flexible member 12 is arranged to locate around a conductor 11 carrying a current to be measured. In particular, the current measuring apparatus 10 comprises a Rogowski coil. The ends of the flexible member 12 are coupled together in use but a gap is created between the ends. This distance can generate errors in the current measurement and the present invention provides compensation means 28 in the form of a compensation windings. The compensation windings comprise a planar spiral conductor provided on a printed circuit board to compensate for the separation distance between the first end and the second end.