Non-Contact DC Current Sensor With Open-Loop Degaussing
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Solution Overview
Problem
Existing non-contact DC current sensors face challenges in tight spaces due to rigid cores and high magnetic remanence, leading to measurement inaccuracies and power inefficiencies, while Rogowski coils are unsuitable for DC current measurement.
Innovation Solution
A flexible, multi-stranded magnetic core with an open-loop AC degaussing signal is used to mitigate magnetic remanence, allowing accurate DC current measurement without complex feedback systems, using a simple AC degaussing signal generator and magnetic field sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rigid clamp sensor with motorized jaws is used to measure DC current, then measurement capability is achieved, but the device becomes heavy and difficult to operate in tight spaces
Solution Approach 1:
The magnetic core is divided into multiple flexible segments or strands that can be bent and shaped to fit around conductors in tight spaces, replacing the single rigid clamp structure. This segmentation maintains measurement capability while dramatically reducing weight and improving flexibility.
Solution Approach 2:
The motorized jaw mechanism is replaced with a flexible magnetic core that can be manually positioned or spring-loaded into place. This eliminates the heavy motor and complex mechanical alignment systems while preserving DC current measurement functionality through the flexible core's ability to conform to the conductor.
2Ease of operation
If a flexible magnetic core is used to improve accessibility in tight spaces, then ease of operation improves, but magnetic remanence increases causing measurement inaccuracies
Solution Approach 1:
An AC degaussing signal is applied periodically or continuously to the flexible magnetic core to prevent magnetic remanence buildup. This periodic magnetic field reversal or randomization eliminates the memory effect that causes measurement errors, allowing the flexible core to maintain both its flexibility and measurement accuracy.
Solution Approach 2:
A degaussing coil wrapped around the flexible magnetic core serves as an intermediary mechanism. This coil generates the AC degaussing signal that acts on the magnetic core to eliminate remanence, separating the flexibility function from the measurement function and allowing both to coexist without interference.
3Measurement precision
If a rigid magnetic core is used to reduce magnetic remanence, then measurement accuracy improves, but the device becomes less flexible and harder to use in tight spaces
Solution Approach 1:
The magnetic core is segmented into multiple flexible strands or sections that can be bent and shaped while maintaining magnetic properties. This segmentation allows the core to adapt to various conductor configurations in tight spaces while the degaussing mechanism prevents remanence issues associated with flexible materials.
Solution Approach 2:
The flexible magnetic core is constructed using composite materials that combine flexibility with magnetic properties. These composite materials allow the core to be flexible like rubber or polymer while maintaining the magnetic characteristics needed for accurate DC current measurement, when combined with the degaussing system.
4Measurement precision
If clamp sensors with large iron jaws are used to measure current, then measurement capability is achieved, but the device causes damage to electrical components in tight spaces
Solution Approach 1:
The heavy iron jaws are replaced with a flexible magnetic core wrapped in protective insulation. This flexible shell structure can be gently placed around conductors without exerting damaging force, while still providing the magnetic path needed for accurate DC current measurement. The flexibility allows the sensor to conform to the conductor shape rather than forcing the conductor into a rigid clamp.
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 provides accurate DC current measurement with reduced power consumption and complexity, enabling convenient use in tight spaces and compatibility with Rogowski coils for versatile current sensing.
Implementation Method 1
an AC degaussing coil wrapped around the loop... an open loop AC degaussing signal (e.g., sine wave, sawtooth wave) may be applied to the flexible multi-stranded magnetic core
Implementation Method 2
The one or more magnetic field sensors can be Hall Effect sensors, for example
Data Source
AI summary
Systems, apparatus, and methods that provide a flexible current sensor capable of measuring current flowing through a conductor without contacting the conductor. In various implementations, a flexible current sensor may have a comparable size, shape, and appearance as a flexible loop of a Rogowski coil, except the current sensor described herein can sense direct current (DC). The current sensors of the present disclosure utilize a novel open loop degaussing mechanism to provide accurate DC current measurements in a conductor. To achieve this, a current sensor includes an AC degaussing coil wrapped around a magnetic core. A driver circuit drives an AC degaussing signal in the AC degaussing core, which operates to reset or degauss the magnetic core, thereby providing more accurate current measurements.