Insulated Current Sensor Using Magnetic Saturation for Avionics
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Solution Overview
Problem
Existing current sensors face challenges in accurately measuring high-voltage currents due to high heat dissipation, sensitivity to temperature variations, and magnetic offset issues, leading to inaccuracies and the need for frequent maintenance, especially in harsh environments like aerospace.
Innovation Solution
A current sensor device featuring a partially wound magnetic core with a primary and secondary coil, an oscillator, and an integrator circuit, which uses a square signal generator to saturate the magnetic core and extract the average current, providing electrical isolation and high accuracy through ampere-turn offsetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a shunt resistor is used to measure current, then the measurement is simple, but heat dissipation is high and accuracy is compromised
Solution Approach 1:
The patent replaces the direct electrical measurement method (shunt resistor) with a magnetic field-based measurement system. The magnetic core and pickup coil detect current through magnetic flux coupling, eliminating the need for direct electrical contact and associated heat dissipation while maintaining measurement simplicity.
Solution Approach 2:
The patent introduces a magnetic core as an intermediary between the measured current and the measurement circuit. The magnetic core concentrates and transmits magnetic flux from the current-carrying conductor to the pickup coil, enabling indirect measurement that avoids the heat dissipation problems of direct resistive measurement.
2Measurement precision
If a Hall-effect sensor is used, then current measurement is achieved, but the sensor is highly sensitive to temperature variations and requires frequent maintenance
Solution Approach 1:
The patent replaces the Hall-effect sensor (which uses semiconductor physics and is temperature-sensitive) with a passive magnetic core and pickup coil system. This electromagnetic induction-based system has no active electronic components in the measurement path, eliminating temperature drift and offset voltage issues inherent in Hall-effect sensors.
Solution Approach 2:
The patent uses a simple, robust magnetic core structure that can withstand harsh environments without degradation. The magnetic core and pickup coil form a passive, maintenance-free system that does not require calibration or replacement due to temperature effects, unlike Hall-effect sensors.
3Loss of energy
If a low-value resistor is used to minimize heat dissipation, then energy loss is reduced, but voltage levels become very low causing significant accuracy loss
Solution Approach 1:
The patent substitutes the voltage measurement approach with a magnetic flux measurement approach. Instead of measuring tiny voltages across low-value resistors, the system measures magnetic flux through the core, which provides sufficient signal strength without requiring high power dissipation, thus avoiding the accuracy-heat dissipation trade-off.
Solution Approach 2:
The patent transitions from electrical domain measurement (voltage across resistor) to magnetic domain measurement (flux through core). This dimensional change allows the system to achieve both low power consumption and high measurement accuracy by operating in a different physical domain where the measurement signal is inherently stronger relative to the energy input.
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 achieves high accuracy and linearity, reduces maintenance needs, and operates effectively across a wide temperature range, suitable for harsh industrial settings such as aerospace applications.
Implementation Method 1
a magnetic core, characterized by its geometric dimensions, its effective length Le and its effective area Ae... whose role is to bring together the field lines created by passing the current Iprim through the main conductor 101
Implementation Method 2
an electronic oscillator connected between an electrical ground and a first terminal of the secondary coil... which uses a square signal generator to saturate the magnetic core
Data Source
AI summary
To produce an insulated current sensor for slaving power devices in the field of avionics, use is made of a magnetic core through which there passes an element traversed by a current to be measured. The magnetic core comprises a secondary winding across the terminals of which are connected an oscillator and a measurement device. The cooperation of the oscillator and of the measurement device makes it possible to circumvent all the traditional drifting of current sensors.