Switched Rogowski Coil Current Sensor for Isolated AC/DC Measurement
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Solution Overview
Problem
Current sensors struggle to accurately measure both AC and DC currents over a wide bandwidth while providing electrical isolation and controllability, especially when measuring low currents, and often require complex signal conditioning due to environmental factors and limited dynamic range.
Innovation Solution
A current sensor combining semiconductor switches with a Rogowski coil and signal conditioning circuit to convert AC/DC currents into a pulsed waveform, allowing for galvanic isolation and wide dynamic range measurements, with the ability to disconnect loads based on control inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If shunt-based current sensors are used to measure high currents, then bandwidth is improved, but electrical isolation is lost and measurement accuracy deteriorates for low currents
Solution Approach 1:
The patent implements dynamic switching between two current paths: a low-resistance shunt path for high currents and a high-resistance path for low currents. The controller dynamically selects the appropriate path based on the current magnitude, enabling accurate measurements across a wide dynamic range while maintaining high bandwidth through the shunt path when needed.
Solution Approach 2:
The patent changes the resistance parameter of the measurement path by switching between a low-resistance shunt (for high currents) and a high-resistance path (for low currents). This parameter change allows the system to optimize for both high-current accuracy and low-current sensitivity, resolving the contradiction between measuring different current ranges effectively.
2Loss of energy
If low-resistance shunt is used to measure high currents, then power dissipation is reduced, but voltage drop becomes too small for accurate measurement of low currents
Solution Approach 1:
The system dynamically switches between a low-resistance shunt path (minimizing power dissipation for high currents) and a high-resistance path (providing sufficient voltage drop for accurate low-current measurement). The controller activates the appropriate path based on current magnitude, resolving the contradiction between power efficiency and measurement accuracy.
Solution Approach 2:
The measurement function is segmented into two separate current paths: one optimized for high currents (low resistance, low power dissipation) and another optimized for low currents (high resistance, high voltage drop). This segmentation allows each path to excel at its designated current range without compromise.
3Reliability
If isolated amplifier is used to achieve galvanic isolation, then electrical isolation is improved, but input characteristics are dictated and dynamic range is restricted
Solution Approach 1:
The patent segments the measurement function into multiple current paths with different resistance values, each optimized for specific current ranges. This segmentation allows the system to maintain galvanic isolation through the isolated amplifier while adapting to a wide dynamic range by selecting the appropriate path for the current being measured.
Solution Approach 2:
The patent creates a universal current sensor that can accurately measure both high and low currents across a wide dynamic range while maintaining galvanic isolation. The multi-functional design incorporates multiple current paths and a controller that automatically selects the optimal path, making the sensor adaptable to various current measurement requirements.
4Device complexity
If passive current sensor is used, then device complexity is reduced, but controllability and ability to disconnect loads is lost
Solution Approach 1:
The patent merges the current sensing function with the load disconnect function into a single integrated device. The semiconductor switches used in the current paths can simultaneously perform measurement and circuit interruption, eliminating the need for separate disconnect devices and reducing overall system complexity while adding controllability.
Solution Approach 2:
The current sensor is designed as a multi-functional device that can both measure currents accurately and disconnect loads when required. The controller manages both measurement and disconnection operations, making the device versatile and reducing the need for additional components in the 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
Enables accurate measurement of both AC and DC currents with wide bandwidth and isolation, minimizing component count and customization, while providing controllability and integration with monitoring systems.
Implementation Method 1
a Rogowski coil current sensor having an aperture. At least one of the first current path and the second current path can pass through the aperture
Data Source
AI summary
An exemplary embodiment of the present disclosure provides a current sensor comprising a current input, a current output, a first current path, and a second current path parallel to the first current path, a Rogowski coil current sensor, and a controller. The first current path can comprise a first switch. When the first switch is in a closed position, current can flow along the first current path between the current input and the current output. The second current path can comprise a second switch. When the second switch is in a closed position, current can flow along the second current path between the current input and the current output. At least one of the first current path and the second current path can pass through an aperture of the Rogowski coil. The controller can be configured to control the first and second switches.