Closed-loop fluxgate current sensor wide range measurement
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Solution Overview
Problem
Conventional closed-loop fluxgate sensors are not well-suited for measuring a wide range of currents, particularly struggling with both small amplitude and large amplitude currents, which is a challenge in applications like battery monitoring and electrical motor control, where currents can vary from milliamperes to hundreds of amperes.
Innovation Solution
A closed-loop fluxgate current sensor using a saturable magnetic core and a secondary coil with an alternating excitation current, where the measuring circuit determines the primary current by measuring the saturation times and average excitation current, allowing for accurate measurement across a large current range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional closed-loop fluxgate sensor is used, then measurement sensitivity for small currents is improved, but measurement range for large currents is limited
Solution Approach 1:
The patent implements dynamic switching between two measurement methods based on the amplitude of the primary current. For small currents, a fluxgate measurement method is used to achieve high sensitivity. For large currents, an alternative measurement method is employed to extend the measurement range. This dynamic adaptation resolves the contradiction by allowing the sensor to optimize its measurement approach based on real-time current conditions.
Solution Approach 2:
The patent changes measurement parameters (measurement method) based on the current amplitude. By detecting the primary current amplitude and switching between different measurement methods accordingly, the sensor maintains high precision for small currents while extending capability for large currents, thus resolving the contradiction between measurement sensitivity and measurement range.
2Measurement precision
If a sensor designed for high precision measurement is used, then accuracy for small currents is improved, but cost increases
Solution Approach 1:
The patent segments the measurement function into two distinct methods: a fluxgate measurement method for small currents and an alternative measurement method for large currents. By dividing the measurement task based on current amplitude ranges, the system achieves high accuracy where needed while using more cost-effective methods for other ranges, thereby reducing overall production costs while maintaining accuracy requirements.
Solution Approach 2:
The patent changes the measurement method parameter based on current amplitude. For small currents where high accuracy is critical, the fluxgate method is used. For large currents, a different measurement method is employed that is more cost-effective to implement. This parameter switching resolves the contradiction between accuracy and production cost.
3Adaptability or versatility
If multiple measurement methods are implemented, then adaptability for different current ranges is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal measurement circuit that can perform multiple measurement methods. The same hardware infrastructure supports both the fluxgate measurement method for small currents and the alternative measurement method for large currents. This multi-functionality approach resolves the contradiction by providing wide current range coverage without proportionally increasing device complexity.
Solution Approach 2:
The patent uses feedback from the primary current amplitude detection to automatically select the appropriate measurement method. The measurement circuit monitors the current amplitude and switches between measurement methods accordingly, eliminating the need for complex manual configuration or multiple independent measurement systems. This feedback-based switching resolves the contradiction between adaptability and device complexity.
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 provides a cost-effective, accurate, and compact current sensor capable of measuring a wide range of currents with high precision, suitable for applications requiring both small and large current measurements.
Implementation Method 1
a secondary coil for applying an alternating excitation current i configured to alternatingly saturate the magnetic core
Implementation Method 2
The magnetic field of the excitation coil saturates the core in an alternating manner. In the presence of a magnetic field, for example an external magnetic field generated by a current flowing in a primary conductor, the saturation characteristic of the soft magnetic core becomes (apparently, as seen from the secondary side) asymmetric
Implementation Method 3
In a closed-loop sensor, this signal is used in a feedback loop to drive a secondary coil on a magnetic circuit configured to cancel the effect of the external magnetic field
Data Source
AI summary
Electrical current sensor comprising a measuring circuit (6) and an inductor (4) for measuring a primary current IP flowing in a primary conductor (2), the inductor comprising a saturable magnetic core (10) made of a highly permeable magnetic material and a secondary coil (12) for carrying an alternating excitation i configured to alternatingly saturate the magnetic core, the coil being connected to the measuring circuit. The measuring circuit is configured to supply a positive or negative voltage to the inductor, to switch off the voltage when a condition signalling saturation is reached, to measure the time to saturation t1 in one direction and the time to saturation t2 in the other direction of the magnetic core and determine therefrom a value of the primary current for small current amplitudes, the measuring circuit being further configured for evaluating the average value of the excitation current i and determining therefrom the value of the primary current for large currents.