Rogowski Coil Self-Calibration via Inductance Measurement
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Solution Overview
Problem
Rogowski coil current transducers face challenges in achieving high accuracy due to sensitivity changes from environmental conditions and aging, requiring costly in-factory calibration and offline processes, while existing calibration methods are either invasive or increase manufacturing costs.
Innovation Solution
A method that measures and corrects the self-inductance of the Rogowski coil using an electronic device, allowing continuous online calibration and diagnosis without interrupting current measurement, using a test current or voltage to determine sensitivity and compensate for changes in coil dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-factory calibration is performed to improve accuracy, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The Rogowski coil performs self-calibration by measuring its own inductance changes. The coil uses its inherent electrical properties (inductance measurement through voltage application and current measurement) to detect dimensional changes and automatically compensate for sensitivity drift, eliminating the need for external calibration equipment and manual intervention.
Solution Approach 2:
The patent replaces mechanical calibration systems (physical measurement devices, manual adjustment mechanisms) with an electrical field-based self-measurement system. The coil uses electrical signals to measure its own inductance and calculate dimensional changes, substituting complex mechanical calibration apparatus with simple electrical measurements.
2Measurement precision
If offline calibration processes are used to improve accuracy, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The calibration process occurs continuously in the background during normal operation. The Rogowski coil continuously measures its inductance and updates sensitivity compensation without interrupting the current measurement function, maintaining uninterrupted useful action for both calibration and measurement.
Solution Approach 2:
The system performs preliminary calibration actions automatically upon installation and continuously thereafter. The self-calibration mechanism is pre-configured to execute calibration routines without requiring external intervention, preparing the system for accurate measurement before actual use begins.
3Measurement precision
If additional reference sensors or windings are added to improve accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The Rogowski coil serves multiple functions: it measures current during normal operation and simultaneously measures its own inductance for self-calibration. The same coil structure and electrical connections are used for both measurement purposes, eliminating the need for separate reference sensors or additional windings.
Solution Approach 2:
The patent merges the calibration function with the measurement function by using the Rogowski coil itself for both purposes. The inductance measurement and current measurement share the same physical structure and electrical circuitry, combining what would traditionally require separate components into a single integrated system.
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 enhances accuracy beyond IEC60044-8 class 0.2, reduces production costs by eliminating the need for in-factory calibration, and provides continuous diagnostic capabilities to detect faulty sensors or incorrect installations.
Implementation Method 1
determining and correcting a sensitivity of the current transducer of the Rogowski type by measuring a self-inductance LRCCT of a coil using the electronic device
Data Source
AI summary
An exemplary method for calibrating a current transducer of the Rogowski type including a Rogowski coil sensor and an electronic device is performed by determining and correcting the sensitivity of the current transducer of the Rogowski type through the measurement of the self-inductance LRCCT of the coil using the electronic device.