Current Measuring Device Using Magnetic Saturation Shift
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Solution Overview
Problem
Current sensors are inadequate for precise detection of small direct and alternating currents due to interference from external magnetic fields, limited sensitivity, and complexity in design, making them unsuitable for applications requiring high accuracy and resistance to external interference.
Innovation Solution
A current measuring device with a magnetic loop magnetized by a periodic signal, using an excitation device to detect shifts in the excitation current caused by the current to be measured, allowing for precise detection of both DC and AC currents without significant external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors based on open magnetic circuit and Hall sensor are used, then small currents can be measured, but measurement results are falsified by external magnetic fields penetrating through the air gap
Solution Approach 1:
The patent converts the harmful effect of external magnetic fields into a useful measurement signal. By intentionally saturating the magnetic core with an AC excitation signal and measuring the DC component of the excitation current that results from the superposition of the measured DC current and the AC excitation, the system transforms potential interference into the measurement mechanism itself. The DC current to be measured causes a DC magnetization component that shifts the operating point of the magnetic core, which is detected through the resulting DC component in the excitation current.
Solution Approach 2:
The patent changes the operating parameters of the magnetic circuit by intentionally driving the magnetic core into saturation with a periodic AC excitation signal. This parameter change allows the system to operate in a nonlinear regime where the DC component of the excitation current becomes a function of the measured DC current, enabling measurement while avoiding the problems of traditional linear operating modes that are susceptible to external field interference.
2Device complexity
If current sensors based on transformer principle are used, then circuit design is simple and no external power supply is required, but direct currents cannot be measured
Solution Approach 1:
The patent creates a universal current sensor that can measure both DC and AC currents using a single device. By superimposing a periodic AC excitation signal on the DC current to be measured and detecting the resulting DC component of the excitation current, the system achieves multi-functionality. The same magnetic core and measurement circuit can handle both direct currents (through their effect on the DC component) and alternating currents (through their effect on the AC component characteristics).
Solution Approach 2:
The patent applies preliminary action by intentionally saturating the magnetic core with a periodic AC excitation signal before the actual measurement takes place. This pre-established saturation state creates a known operating condition that allows the DC current to be measured through its effect on the DC component of the excitation current, enabling DC measurement capability that would otherwise require a completely different sensor type.
3Adaptability or versatility
If current sensors based on magnetic multivibrator method are used, then direct currents can be recorded, but sensitivity is low and measurement results are influenced by supply voltage
Solution Approach 1:
The patent employs feedback by continuously monitoring the excitation current and using its DC component as a direct indication of the measured DC current. The periodic saturation and demagnetization of the magnetic core creates a feedback mechanism where the excitation current's DC component automatically reflects the magnitude of the measured current, providing stable and sensitive measurement that is independent of supply voltage variations.
4Measurement precision
If universal current sensors capable of measuring very small currents with high accuracy are used, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent introduces an intermediary AC excitation signal as a mediator between the DC current to be measured and the measurement system. This intermediary signal facilitates the measurement process by creating a detectable DC component in the excitation current that reflects the measured DC current, while avoiding the need for complex sensor circuits. The magnetic core acts as an intermediary that couples the DC and AC components in a measurable way.
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 simple, highly accurate, and robust method for detecting currents, capable of operating in environments with external interference, with a design that is not influenced by external magnetic fields and can measure currents up to several amperes with high precision.
Implementation Method 1
an excitation device which is designed to magnetize the magnetic loop by means of such a periodic signal that the excitation current always oscillates between two saturation limits
Implementation Method 2
a first current sensor, which is designed to detect an excitation current flowing in the excitation device due to the periodic signal and/or the current to be detected
Data Source
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AI summary
The invention relates to a current measuring device for detecting a current flowing through a power line, said device comprising: a magnetic loop for receiving the power line; an excitation device designed to magnetise the magnetic loop by means of a periodic signal; a first current sensor designed to detect an exciting current flowing in the excitation device on the basis of the periodic signal and/or the current to be detected; and a determination device that determines a shift of the detected exciting current on the current axis, said shift being caused by the current, and, as a result, deduces the intensity of the current to be detected. The invention also relates to a solar inverter and to a method for detecting a current.