Active Circuit Maintains Zero Burden Resistance for Wide Range Current Sensing
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Solution Overview
Problem
Current sensing devices face challenges in accurately measuring a wide range of currents due to the need for different sizes of current transformer coils, which requires adjustments in the number of turns and burden resistor values, leading to errors and complexities in electronic circuitry.
Innovation Solution
A system using a family of current transformer coils with the same number of turns and wire size, coupled with an active circuit that maintains a burden resistance value of zero, allowing for accurate current measurement across a wide range of conductor sizes by directing virtually all current through a burden resistor, independent of impedance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different sizes of current transformer coils are used to accommodate different conductor sizes, then the measurement precision for different current ranges is improved, but the device complexity increases due to the need for multiple coil sizes and corresponding burden resistor adjustments
Solution Approach 1:
The patent applies universality by designing a single transformer coil configuration that can measure multiple current ranges through an active circuit that dynamically adjusts the burden resistance. The same coil serves multiple functions across different current measurement scenarios, eliminating the need for multiple coil sizes and fixed burden resistor configurations.
Solution Approach 2:
The patent implements dynamics by using an active circuit that dynamically adjusts the burden resistance value based on the current range being measured. The burden resistance is not fixed but is actively controlled to maintain optimal measurement conditions across different current levels, allowing a single coil to accurately measure from sub-Ampere to thousands of Amperes.
2Measurement precision
If the number of turns or burden resistor value is changed to match different current ranges, then the measurement precision for different current ranges is improved, but the ease of operation deteriorates due to manual adjustment requirements and potential errors in selection
Solution Approach 1:
The patent applies self-service by implementing an active circuit that automatically adjusts the burden resistance based on the measured current level. The system monitors the current range and self-regulates the burden resistance accordingly, eliminating the need for manual intervention, selection, or adjustment by the operator.
Solution Approach 2:
The patent implements feedback by using the active circuit to continuously monitor the current measurement and dynamically adjust the burden resistance in response to the measured current level. This closed-loop control ensures optimal measurement precision across different current ranges without requiring manual reconfiguration.
3Adaptability or versatility
If larger transformer coil windows are used to accommodate multiple conductors for ground fault detection, then the adaptability for different conductor configurations is improved, but the measurement precision for small current values deteriorates due to increased window size requirements
Solution Approach 1:
The patent applies dynamics by using an active circuit that dynamically adjusts the burden resistance to maintain optimal measurement conditions. When measuring small currents with larger coil windows, the active circuit increases the burden resistance to compensate for the reduced current density, thereby maintaining measurement precision across different conductor configurations.
Solution Approach 2:
The patent implements parameter changes by dynamically modifying the burden resistance value based on the current range and conductor configuration. The active circuit adjusts this critical parameter in real-time to maintain the relationship between the transformer coil impedance and burden resistance, ensuring accurate measurements regardless of window size or conductor arrangement.
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
Enables accurate current measurement in single-phase and multi-phase systems, including ground fault detection, with minimal error and adaptive configuration for varying current ranges, using the same conditioning and monitoring circuitry across different transformer coil sizes.
Implementation Method 1
pass a conductor through a ring-like coil and measure current induced in the coil resulting from the field produced by a current flowing through the conductor
Data Source
AI summary
A current measurement technique is disclosed in which a family of transformer coils having the same number of turns and the same winding resistance may be associated an active circuit for presenting a burden resistance of substantially zero value. The impedance of the coils will vary with their window size, and the active circuitry will reduce the burden resistance accordingly so that reductions and impedance do not result in introducing additional error into measurements. The circuitry may be used for measuring current in single conductors or in multiple conductors passing through the transformer coil, such as for ground fault measurement, monitoring and control.