Rogowski Torus Sensor Support for Dimensional Stability
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Solution Overview
Problem
Rogowski toroid current measurement sensors face challenges in achieving high precision due to dimensional variations caused by temperature fluctuations and manufacturing shrinkage, especially in harsh environments, which affect the accuracy of the output signal.
Innovation Solution
A Rogowski torus sensor with a support made of molded rigid plastic material featuring outer recesses with grooves and partitions, and a section shape that minimizes shrinkage and thermal expansion, using an amorphous resin with glass fibers for improved dimensional stability and thermal coefficient matching copper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rigid plastic support is used for mass production, then ease of manufacture is improved, but measurement precision deteriorates due to dimensional variations
Solution Approach 1:
The patent changes the material parameters by selecting a specific rigid plastic material with controlled shrinkage characteristics and thermal expansion coefficient. The support is designed with specific dimensional parameters including a circular cross-section with diameter between 10-30mm, and wall thickness between 2-5mm, which optimizes the balance between manufacturability and measurement precision.
Solution Approach 2:
The patent applies local quality by creating a hollow cylindrical structure with specific wall thickness distribution, and by adding surface treatments or coatings to critical measurement areas. The support structure has different properties in different regions - the wall thickness is optimized to minimize dimensional variations while maintaining ease of injection molding.
2Measurement precision
If calibration system is used to achieve better than 1% accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the support structure self-calibrating by designing it with inherent dimensional stability. The rigid plastic material and optimized geometry allow the support to maintain its shape and dimensions without requiring external calibration systems. The support essentially calibrates itself through its material properties and structural design.
Solution Approach 2:
The patent extracts and removes the calibration system from the overall device, achieving measurement precision through the support structure itself rather than through separate calibration equipment or complex adjustment mechanisms.
3Adaptability or versatility
If support section dimensions change due to temperature variations, then adaptability to extreme environments is improved, but measurement precision deteriorates
Solution Approach 1:
The patent selects a rigid plastic material with specific thermal properties, particularly a low coefficient of thermal expansion. The support is designed to operate across a wide temperature range (-40°C to 180°C) while maintaining dimensional stability. The material parameters are chosen to minimize thermal deformation of the support structure.
Solution Approach 2:
The patent explicitly addresses thermal expansion by selecting materials and designing the support geometry to compensate for or minimize thermal effects. The rigid plastic material is chosen for its low thermal expansion characteristics, and the support structure is designed with appropriate clearances and stress distribution to handle thermal cycling without affecting measurement precision.
4Manufacturing precision
If molding shrinkage is controlled for high precision, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent optimizes the molding process parameters including injection pressure, temperature, and cooling time to achieve consistent dimensional accuracy. The support geometry is designed with appropriate draft angles, wall thickness uniformity, and rib configurations that facilitate easy molding while controlling shrinkage. The material selection includes rigid plastics with predictable shrinkage characteristics.
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 enables precise current measurement with accuracy better than 1% and reduced sensitivity to temperature variations, ensuring reliable performance across extreme temperatures.
Implementation Method 1
using an amorphous resin with glass fibers for improved dimensional stability and thermal coefficient matching copper
Implementation Method 2
a secondary winding wound on said support to provide an electrical signal representative of a current flowing in a conductor passing through the inside of the toroid
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The Rogowski coil current sensor comprises a support (1) made of non-magnetic material and a secondary winding (5) wound on said support (1) to provide an electrical signal representative of a current flowing in a conductor passing through the interior of the torus. The support (1) is made essentially of molded rigid plastic and has at least one external recess (2, 3) distributed along the length of the support body. The recess (2) has at least two grooves (3) separated by a partition (4). The measuring and protection device and the electrical circuit breaker include such a current sensor.