Rogowski Coil Low Permeability Magnetic Core
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Solution Overview
Problem
Rogowski coils with non-magnetic cores produce low output voltage, leading to issues with electromagnetic interference (EMI) and increased complexity and cost due to the need for amplification in metering applications, while existing solutions do not provide sufficient output voltage.
Innovation Solution
A Rogowski coil with a magnetic core having a relative permeability greater than one and less than twenty, which includes a winding disposed in a helical coil about a toroid core body, reducing the need for signal amplification by generating a detectable voltage without external amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-magnetic core material is used, then saturation at high currents is avoided, but the output voltage becomes very low
Solution Approach 1:
The patent changes the magnetic parameter (relative permeability) of the core material from very low (non-magnetic) to a specific low range (greater than one and less than twenty). This parameter modification allows the core to provide sufficient magnetic coupling for adequate output voltage while maintaining resistance to saturation at high currents, thus resolving the contradiction between output voltage and saturation resistance.
2Reliability
If a non-magnetic core is used, then saturation is avoided, but the output assembly complexity increases due to required amplification
Solution Approach 1:
By modifying the core material's relative permeability to a low range (greater than one and less than twenty), the patent achieves sufficient output voltage that eliminates or reduces the need for amplification circuits in the output assembly. This resolves the contradiction by maintaining saturation resistance while reducing output assembly complexity.
3Power
If a magnetic core with higher permeability is used, then output voltage increases, but saturation occurs at lower currents
Solution Approach 1:
The patent precisely controls the relative permeability parameter within a specific range (greater than one and less than twenty). This constrained parameter change optimizes the balance between achieving sufficient output voltage and maintaining resistance to saturation, resolving the contradiction by avoiding both extremely low permeability (insufficient voltage) and high permeability (early saturation).
Solution Approach 2:
The core is constructed from composite material containing ferromagnetic particles dispersed in a non-magnetic binder matrix. This composite structure provides controlled magnetic properties with relative permeability in the desired low range, achieving both adequate output voltage and saturation resistance that neither pure magnetic nor pure non-magnetic materials could provide alone.
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 Rogowski coil with a magnetic core achieves a transfer impedance of between 1mV/A and 20mV/A, providing a non-amplified signal that is detectable by the output assembly, reducing the need for amplification and addressing the low output voltage issues.
Implementation Method 1
The voltage that is induced in the coil is proportional to the rate of change (derivative) of current in the straight conductor
Implementation Method 2
The core has a low relative permeability. Magnetic permeability is related to magnetic saturation that affects the output of the Rogowski coil
Data Source
Figure 1
AI summary
A Rogowski coil includes a magnetic core and a winding. The magnetic core includes an encircling body. The winding includes a conductive wire. The winding is disposed in a generally helical coil about the core body.