Rogowski Current Transformer Phase Error Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring alternating current using Rogowski coils face challenges such as frequency-dependent angle and amplitude errors, high circuit complexity, and crosstalk issues, which affect measurement accuracy and require complex and costly digital integration solutions.
Innovation Solution
A method involving a Rogowski coil that calculates a current prediction value by forming and extrapolating from sliding averages and sums of output voltage values, with offset correction using amplifiers and AD converters, to minimize phase errors and circuit complexity while maintaining measurement accuracy across a wide current range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital numerical integration using ASIC or FPGA is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex digital integration circuits (ASIC/FPGA) with a simplified computational method implemented in a microcontroller. Instead of using dedicated hardware integration circuits, the invention uses software-based numerical integration algorithms that process the voltage signal from the Rogowski coil, thereby reducing hardware complexity while maintaining measurement precision.
2Device complexity
If integration is carried out using an analog integrator, then device complexity is reduced, but measurement precision deteriorates due to frequency-dependent errors
Solution Approach 1:
The patent changes the integration method from analog to digital, allowing the integration parameters to be adjusted through software rather than fixed hardware characteristics. This enables the system to achieve accurate integration across different frequencies without the frequency-dependent errors inherent in analog integrators, while keeping the overall device complexity low through microcontroller implementation.
3Measurement precision
If Rogowski coils are wound with sufficient precision to reduce crosstalk, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the microcontroller monitors the voltage signal from the Rogowski coil and applies correction algorithms to compensate for crosstalk effects. This software-based compensation reduces the need for extremely precise manual winding, thereby improving ease of manufacture while maintaining measurement precision through active correction of manufacturing tolerances.
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
This approach achieves a small phase error with relatively low circuit complexity, improving measurement accuracy and reducing crosstalk, thereby providing precise alternating current measurement with reduced circuit complexity and cost.
Implementation Method 1
If the Rogowski coil completely encloses a current conductor (current path) carrying alternating current, a voltage is generated as the output variable that is proportional to the first derivative of the alternating current over time
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to a method and a device (MD) comprising a Rogowski current transformer for measuring an alternating current (I(t)), which at a first time (t0) assumes a present current value (I(t0)), wherein the Rogowski coil (RC) generates a first analogue alternating voltage (Urc(t)), the digital voltage values (Uti) of which at a first time (t0) assume a present first voltage value (Ut0). In order to attain a low phase error over a large current measurement range, it is proposed that: each present first voltage value (Ut0) is added to a first sum value (S1i) and thus a present first sum value (S10) is formed; a first mean value (M10) is formed from the first sum values (S1i) following on from one another continuously, is subtracted from the present first sum value (S10), and thus a present second sum value (S20) is formed; a present second mean value (M20) is formed from the second sum values (S2i), is subtracted from the present second sum value (S20), and thus a present third sum value (S30) is formed; and a present prediction value (Vt1out) is calculated on the basis of present third sum values (S3i), and an analogue alternating voltage (Up2out (t), Ua(t)) is formed from the prediction values (Vtiout).