Rogowski Coil Calibration Circuit for Stable Current Measurement
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Solution Overview
Problem
Rogowski coils suffer from inconsistencies in output voltage due to variations in coil turn numbers, requiring improved precision for accurate current measurement.
Innovation Solution
A Rogowski coil integrated with a calibration unit that modifies output voltage based on a predetermined calibration factor and includes temperature compensation to account for temperature-induced variations, using components like resistors, potentiometers, and negative temperature coefficient thermistors to adjust resistance dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If individual coils are precisely cut from a lengthy coil during manufacturing, then the coil length can be controlled, but the coil turn number varies and causes inconsistency in output voltage
Solution Approach 1:
The patent introduces a calibration unit that dynamically adjusts the output voltage by changing electrical parameters (resistance values) to compensate for variations in coil turn number. This allows the system to maintain consistent output voltage despite manufacturing variations in coil parameters.
Solution Approach 2:
The calibration unit receives feedback about the actual output voltage and adjusts the resistance values accordingly to achieve the desired output. This closed-loop approach ensures that variations in coil turn number do not affect the final measurement accuracy.
2Device complexity
If the Rogowski coil operates without temperature compensation, then the device structure remains simple, but temperature variations cause measurement inaccuracies
Solution Approach 1:
The calibration unit includes temperature compensation circuitry that dynamically adjusts resistance values based on temperature conditions. This allows the system to maintain measurement accuracy across varying temperatures without requiring a completely different coil design.
Solution Approach 2:
The calibration unit acts as an intermediary between the Rogowski coil and the measurement system, compensating for temperature effects on the coil's electrical characteristics. This mediator approach allows the original coil design to remain simple while achieving temperature-stable measurements.
3Power
If the coil turn number is increased to improve measurement sensitivity, then the output voltage increases, but the manufacturing precision and consistency deteriorate
Solution Approach 1:
Rather than relying solely on precise control of coil turn number, the patent uses the calibration unit to adjust electrical parameters (resistance values) to achieve the desired output voltage. This shifts the precision requirement from mechanical manufacturing to electrical calibration, which can be done more accurately.
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 enhances measurement accuracy by compensating for coil turn variations and temperature effects, ensuring precise and reliable current measurements across varying conditions.
Implementation Method 1
Rogowski coil configured to generate an output voltage proportionate to the rate of change of a primary current passing through a conductor
Implementation Method 2
negative temperature coefficient thermistors to adjust resistance dynamically
Data Source
AI summary
The invention provides a current measurement device for a primary conductor. The device utilizes a Rogowski coil to generate an output voltage proportional to the rate of change of the primary current flowing through the conductor. The device also includes a calibration unit, operatively connected to the Rogowski coil. The calibration unit is designed to modify the output voltage using a predefined calibration factor, which is determined based on a physical attribute of the Rogowski coil. The device allows for accurate measurement of the current by considering the unique physical characteristics of the coil used in the measurement process.