Shunt Resistor and Rogowski Coil Current Sensor
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Solution Overview
Problem
Current methods for measuring high-power switching currents face challenges such as insertion inductance, limited bandwidth, and inability to accurately measure large and rapidly changing currents due to issues with Rogowski coils, current transformers, and coaxial shunts, particularly at high frequencies.
Innovation Solution
A test and measurement accessory device with a shunt structured as a washer, minimizing electrical path length and inductance, combined with a Rogowski coil to achieve DC capabilities and broad measurement bandwidth, using a compensating pole to cancel mutual inductance and optimize coil design for high-frequency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a Rogowski coil is used to measure high-frequency currents, then bandwidth is improved, but DC measurement capability is lost
Solution Approach 1:
The patent combines a Rogowski coil (for AC/high-frequency measurement) with a shunt resistor (for DC/low-frequency measurement) into a single integrated current sensor assembly. The Rogowski coil provides broadband AC measurement capability while the shunt resistor maintains DC measurement capability, resolving the contradiction between bandwidth improvement and DC capability preservation.
2Adaptability or versatility
If a shunt resistor is used to measure current, then DC and low-frequency measurement is improved, but bandwidth is limited due to inductive drop
Solution Approach 1:
The integrated sensor assembly merges the shunt resistor's DC measurement strength with the Rogowski coil's high-frequency capability. The shunt resistor handles DC and low-frequency components while the Rogowski coil captures high-frequency transients, achieving broad bandwidth without sacrificing DC measurement capability.
3Measurement precision
If a coaxial shunt is used to eliminate measurement inductance, then measurement accuracy at high frequency is improved, but insertion inductance increases
Solution Approach 1:
The patent extracts the measurement function from the current path by using a Rogowski coil that measures magnetic field externally, rather than placing a shunt directly in the current path. This eliminates insertion inductance while maintaining measurement accuracy through the coil's broadband response.
4Object-generated harmful factors
If the electrical path length through a shunt is extended to reduce insertion inductance, then insertion inductance is reduced, but measurement inductance increases
Solution Approach 1:
The Rogowski coil extracts the measurement function from the physical current path, measuring current indirectly through magnetic field sensing. This allows the electrical path to be minimized for low insertion inductance while the coil's compact winding minimizes its own self-inductance, avoiding the trade-off between insertion and measurement inductance.
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 effectively measures high-power switching currents with minimized inductance and extended bandwidth, maintaining accuracy across a wide range of frequencies while reducing magnetic flux pickup and power dissipation.
Implementation Method 1
A Rogowski coil senses the time derivative of this magnetic field; the voltage induced on the Rogowski coil can then be integrated to determine the current flow.
Implementation Method 2
One approach often used is to place a series resistor (or 'shunt') in the current path, measure the voltage drop caused by the current, and divide by the resistance.
Implementation Method 3
using a compensating pole to cancel mutual inductance and optimize coil design for high-frequency operation
Data Source
AI summary
A current measurement device with a shunt resistor of a resistive core with an opening and measurement leads, a Rogowski coil with electrical contacts surrounding the resistive core, conductive layers on first and second sides of the resistive core, one or more insulative layers between the conductive layers and the Rogowski coil, the current measurement device configured to combine signals from the shunt resistor and the Rogowski core. The current measurement device may have a Rogowski coil on a flexible substrate at least partially wrapped around the shunt resistor. A current measurement device has a rigid substrate, vias filled with a conductive material through the rigid substrate, conductive layers on the top surface and the bottom surface connecting to the vias to form a Rogowski coil structure, one or more insulative layers directly on the coil structure, a shunt resistor directly on the one or more insulative layers.