Wireless Rogowski Coil for High-Current Measurement
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Solution Overview
Problem
Conventional current measurement tools, such as multimeters and Rogowski coils, face limitations in convenience, safety, and flexibility, especially in confined spaces, due to the need for physical contact and the constraints of magnetic cores and cables, which can be hazardous and impractical for high-current measurements.
Innovation Solution
A wireless remote-controlled Rogowski coil system that uses an elongated coil with an integrator circuit and analog-to-digital converter to measure current without physical contact, allowing for safe and flexible placement of the coil and transmission of data to a multimeter or control device, reducing the need for internal fuses and improving safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wired Rogowski coil is used to measure current, then current measurement capability is improved, but the parasitic resistance, capacitance and inductance of the connecting cable increase, limiting the distance between the coil and the technician
Solution Approach 1:
The patent extracts the signal processing functions (integrator, analog-to-digital converter, transmitter) from the Rogowski coil itself and places them in a separate remote device. This allows the coil to be positioned close to the conductor for accurate measurement while the processing electronics are located remotely, eliminating the need for long connecting cables and their associated parasitic effects.
Solution Approach 2:
The patent introduces a wireless communication intermediary (transmitter and receiver) to transfer measurement data from the Rogowski coil to the display device without requiring physical cable connections. This mediator eliminates the parasitic effects of cables while maintaining data transmission capability.
2Ease of operation
If a clamp-on multimeter with magnetic core is used, then current measurement is enabled without breaking the circuit, but the magnetic core becomes saturated at high current levels, limiting measurement capability
Solution Approach 1:
The patent changes the fundamental parameter of the sensing element from a magnetic core to an air-core Rogowski coil. This parameter change eliminates magnetic saturation effects, allowing the system to measure very high current levels (up to 100 kA or more) without the limitations imposed by magnetic material saturation.
3Measurement precision
If a clamp-on multimeter with mechanical jaws is used, then current measurement is enabled, but the device requires large physical space to open and close the jaws, making it difficult to use in confined spaces
Solution Approach 1:
The patent segments the measurement system into two independent parts: a flexible Rogowski coil that can be easily positioned around conductors in confined spaces, and a separate processing unit. The coil can be manipulated independently without requiring large mechanical jaw movements, enabling use in tight electrical cabinets and confined areas.
Solution Approach 2:
The Rogowski coil is constructed with flexible wiring and lacks rigid mechanical jaws, allowing it to be easily bent and positioned around conductors in confined spaces. The flexible construction enables the coil to adapt to various conductor shapes and locations without requiring large opening/closing movements.
4Measurement precision
If general purpose multimeter with internal current shunt is used, then current measurement is enabled, but the maximum current is limited to ten amperes due to test lead and circuitry capacity
Solution Approach 1:
The patent extracts the high-current sensing function from the multimeter body and places it in an external Rogowski coil. This allows the multimeter to measure current beyond its internal circuitry capabilities by using the coil's air-core design that can handle very high currents without damage to the multimeter's internal components.
Solution Approach 2:
The Rogowski coil acts as an intermediary device that senses high currents and converts them to proportional voltage signals that can be safely processed by the multimeter. This mediator protects the multimeter from exposure to high currents while enabling measurement of such currents.
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 safe and flexible current measurement in confined spaces with reduced parasitic effects from cables, allowing for higher current measurement capabilities and improved user safety by eliminating the need for physical contact and internal fuses, while maintaining accuracy and convenience.
Implementation Method 1
The current clamp is closed around the current-carrying conductor, which may include copper wires and buss bars, to sense the magnetic field created by the current flow
Implementation Method 2
The voltage is integrated by an integrator circuit or device to provide an output signal representative of current in the conductor
Data Source
AI summary
A Rogowski coil in a sensor unit has voltage induced by a conductor surrounded by the Rogowski coil. The voltage is integrated to represent current which is converted to digital data representing current in the conductor and sent wirelessly to a multimeter. The sensor unit may receive control signals from the multimeter and a remote control apparatus. A plurality of sensor units may be networked and controlled by the remote control apparatus.